Tech Arsenal 1/Tech Arsenal (Arsenal Computer).ISO/tek-05/man_9106.zip/KA9QNOS.TXT

Text File | 1991-06-11 | 154KB | 4,489 lines

             NET User Reference Manual (NOS Version)


                         Phil Karn, KA9Q






1.  The NET.EXE Program

The MS-DOS executable file net.exe  provides  Internet  (TCP/IP),
NET/ROM  and AX.25 facilities.  Because it has an internal multi-
tasking operating system, net.exe can  act  simultaneously  as  a
client, a server and a packet switch for all three sets of proto-
cols. That is, while a local user accesses remote  services,  the
system can also provide those same services to remote users while
also switching IP, NET/ROM and AX.25 packets and  frames  between
other client and server nodes.

The keyboard and display is used by the local operator to control
both host and gateway level functions, for which a number of com-
mands are provided.

1.1.  Installation

Net.exe uses the following directory structure:

        /spool
        /spool/help
        /spool/mail
        /spool/mqueue
        /spool/rqueue
        /spool/news


By default, the /spool directory is placed in the root  directory
of  the  current  drive. However, a subdirectory may be specified
with the -d command-line option described below. If  a  subdirec-
tory  is  given,  the alias, autoexec.net, dialer, domain.txt and
ftpusers configuration files must also be located there.

The "/spool" directory and its sub-directories are  used  by  the
bbs,  SMTP  and  NNTP services.  The areas, forward.bbs, history,
mail.log, rewrite and signatur configuration  files  are  located
here.

1.2.  net [-b] [-s <sockets>] [-d <directory>] [<startup file>]





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1.2.1.  -b

The -b option specifies the use of BIOS for console  output;  the
default  is  to  write  directly to the video display buffer. Use
this option if you are running under a windowing package and have
trouble with output "bleeding through" on top of other windows.

1.2.2.  -s

The -s option specifies the size of the socket array to be  allo-
cated  within  net.exe. This limits the number of network connec-
tions that may exist simultaneously.  The default is 40.

1.2.3.  -d

The -d option allows the user to specify a directory for the con-
figuration  and spool files; it defaults to the root directory of
the system.

1.2.4.  Startup file

After all command-line options, the name of a startup file may be
specified.   If no startup file is specified, net.exe attempts to
open a file named autoexec.net in the configuration directory  of
the  current  drive.  If the file exists, it is read and executed
as though its contents were typed on  the  console  as  commands.
(See  the Commands chapter.) This feature is useful for attaching
communication  interfaces,  configuring  network  addresses,  and
starting the various services.

2.  Console modes

The console may be in one of two modes: command mode and converse
mode.   In  command mode, the prompt net> is displayed and any of
the commands described in the Commands chapter  may  be  entered.
In  converse  mode,  keyboard input is processed according to the
current session.

Sessions come in many types, including Telnet, FTP, AX25, NETROM,
Ping,  More, Hopcheck and Tip.  In a Telnet, AX25, NETROM, or Tip
session, keyboard input is sent to the remote system and any out-
put from the remote system is displayed on the console.  In a FTP
session, keyboard input is first examined to see if it is a known
local  command;  if  so  it  is  executed locally.  If not, it is
"passed through" to the remote FTP server.  (See the FTP  Subcom-
mands  chapter).  In a Ping session the user may test the path to
a remote site, and in a More session,  the  user  may  examine  a
local file. A Hopcheck session is used to trace the path taken by
packets to reach a specified destination. A Tip session  provides
a "dumb terminal" service that bypasses all network protocols.

The keyboard also has cooked and raw states.   In  cooked  state,
input  is line-at-a-time; the user may use the line editing char-
acters ^U, ^R and backspace to erase the line, redisplay the line



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and  erase  the  last  character,  respectively.   Hitting either
return or line feed passes the complete line up to  the  applica-
tion.   In raw state, each character is immediately passed to the
application as it is typed.

The keyboard is always in cooked state in command  mode.   It  is
also  cooked in converse mode on an AX25, FTP or NET/ROM session.
In a Telnet session it depends on  whether  the  remote  end  has
issued  (and  the  local  end  has accepted) the Telnet WILL ECHO
option (see the echo command).

On the IBM-PC, the user may escape back to command mode  by  hit-
ting  the  F10  key.   On  other systems, the user must enter the
escape character, which is by default control-]  (hex  1d,  ASCII
GS).  (Note that this is distinct from the ASCII character of the
same name).  The escape character can be changed (see the  escape
command).

In the IBM PC version, each session (including the command  "ses-
sion")  has  its  own screen.  When a new session is created, the
command display is saved in memory and  the  screen  is  cleared.
When  the  command  escape  key (usually F10) is hit, the current
session screen is saved and the command screen is restored.  When
a  session  is  resumed,  its  screen  is  restored exactly as it
appeared when it was last current.

3.  Commands

This chapter describes the commands recognized in  command  mode,
or  within  a startup file such as autoexec.net.  These are given
in the following notation:

        command
        command literal_parameter
        command subcommand <parameter>
        command [<optional_parameter>]
        command a | b


Many commands  take  subcommands  or  parameters,  which  may  be
optional  or  required.  In  general, if a required subcommand or
parameter is omitted, an error message will summarize the  avail-
able  subcommands or required parameters.  (Giving a '?' in place
of the subcommand will also generate the message.  This is useful
when  the  command  word  alone is a valid command.) If a command
takes an optional value parameter, issuing  the  command  without
the  parameter  generally displays the current value of the vari-
able. (Exceptions to this rule are noted in the  individual  com-
mand descriptions.)

Two or more parameters separated  by  vertical  bar(s)  denote  a
choice  between  the  specified  values.  Optional parameters are
shown enclosed in [brackets], and a parameter enclosed in  <angle
brackets> should be replaced with an actual value or string.  For



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example, the notation <hostid> denotes an actual host or gateway,
which  may  be  specified  in  one  of  two ways: as a numeric IP
address in dotted decimal notation (eg. 44.0.0.1), or as  a  sym-
bolic name listed in the file domain.txt.

All commands and many subcommands may be  abbreviated.  You  only
need  type enough of a command's name to distinguish it from oth-
ers that begin with the same series of letters. Parameters,  how-
ever, must be typed in full.

Certain FTP subcommands (eg. put, get, dir, etc)  are  recognized
only  in converse mode with the appropriate FTP session; they are
not  recognized  in  command  mode.   (See  the  FTP  Subcommands
chapter.)

Note that certain commands may have  been  configured  out  of  a
given  copy of net.exe to save disk and memory.  If a command has
been configured out, it will not appear in the list  produced  by
the  "?" command, nor will it be recognized by the command inter-
preter.

3.1.  <CR>

Entering a carriage return (empty line)  while  in  command  mode
puts  you  in converse mode with the current session. If there is
no current session, net.exe remains in command mode.

3.2.  !

An alias for the shell command.

3.3.  #

Commands starting with the hash mark (#)  are  ignored.  This  is
mainly useful for comments in the autoexec.net file.

3.4.  abort [<session #>]

Abort a FTP get, put or dir  operation  in  progress.  If  issued
without  an  argument, the current session is aborted. (This com-
mand works only on FTP sessions.) When receiving  a  file,  abort
simply  resets the data connection; the next incoming data packet
will generate a TCP RST (reset)  response  to  clear  the  remote
server.   When  sending  a  file, abort sends a premature end-of-
file. Note that in both cases abort will leave a partial copy  of
the  file on the destination machine, which must be removed manu-
ally if it is unwanted.

3.5.  arp

Display the  Address  Resolution  Protocol  table  that  maps  IP
addresses to their subnet (link) addresses on subnetworks capable
of broadcasting.  For each IP address entry the subnet type  (eg.
Ethernet, AX.25), subnet address and time to expiration is shown.



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If the link address  is  currently  unknown,  the  number  of  IP
datagrams awaiting resolution is also shown.

3.5.1.  arp add <hostid> ethernet |  ax25  <ethernet  address>  |
<ax25_address>

Add a permanent entry to the table. It will not time out as  will
an  automatically-created entry, but must be removed with the arp
drop command.

3.5.2.  arp publish <hostid> ethernet | ax25 <ethernet address> |
<ax25_address>

This command is similar to the arp add command, but  system  will
also respond to any ARP request it sees on the network that seeks
the specified address.  Use this feature with great care.

3.5.3.  arp drop <hostid> ax25 | ethernet

Remove the specified entry from the ARP table.

3.5.4.  arp flush

Drop all automatically-created entries in  the  ARP  table.  Per-
manent entries are not affected.

3.6.  asystat

Display statistics on attached asynchronous communications inter-
faces  (8250  or  16550A), if any. The display for each port con-
sists of three lines. The first line gives the port label and the
configuration  flags; these indicate whether the port is a 16550A
chip, the trigger character if any, whether CTS flow  control  is
enabled,  whether  RLSD (carrier detect) line control is enabled,
and the speed in bits per second.  (Receiving the trigger charac-
ter causes the driver to signal upper layer software that data is
ready; it is automatically set to the appropriate frame end char-
acter for SLIP, PPP and NRS lines.)

The second line of the status display shows receiver  (RX)  event
counts:  the total number of receive interrupts, received charac-
ters, receiver overruns (lost characters) and the  receiver  high
water mark.  The high water mark is the maximum number of charac-
ters ever read from the device during a single interrupt. This is
useful  for  monitoring  system  interrupt  latency margins as it
shows how close the port hardware has come to overflowing due  to
the  inability  of  the CPU to respond to a receiver interrupt in
time. 8250 chips have no FIFO, so the high water mark  cannot  go
higher  than  2  before overruns occur. The 16550A chip, however,
has a 16-byte receive FIFO which the software programs to  inter-
rupt  the  CPU when the FIFO is one-quarter full.  The high water
mark should typically be 4 or 5 when a  16550A  is  used;  higher
values  indicate  that  the  CPU  has  at least once been slow to
respond to a receiver interrupt.



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When the 16550A is  used,  a  count  of  FIFO  timeouts  is  also
displayed  on  the  RX status line. These are generated automati-
cally by the 16550A when three character  intervals  go  by  with
more  than  0  but  less than 4 characters in the FIFO. Since the
characters that make up a SLIP or NRS frame are normally sent  at
full  line speed, this count will usually be a lower bound on the
number of frames received on the port, as only the last  fragment
of a frame generally results in a timeout (and then only when the
frame is not a multiple of 4 bytes long.)

Finally, the software fifo  overruns  and  high  water  mark  are
displayed.  These indicate whether the <bufsize> parameter on the
attach command needs to be  adjusted  (see  the  Attach  Commands
chapter).

The third line shows transmit (TX) statistics, including a  total
count  of transmit interrupts, transmitted characters, the length
of the transmit queue in bytes, the number of status  interrupts,
and the number of THRE timeouts.  The status interrupt count will
be zero unless CTS flow control or RLSD  line  control  has  been
enabled.   The  THRE  timeout  is a stopgap measure to catch lost
transmit interrupts, which seem to happen when there is a lot  of
activity (ideally, this will be zero).

3.7.  attach <hw type> ...

Configure  and  attach  a  hardware  interface  to  the   system.
Detailed  instructions for each driver are in the Attach Commands
chapter.  An easy way to  obtain  a  summary  of  the  parameters
required  for a given device is to issue a partial attach command
(eg. attach packet).  This produces a usage  message  giving  the
complete command format.

3.8.  ax25 ...

These commands are used to control the AX.25 amateur  radio  link
level protocol.

3.8.1.  ax25 blimit [<count>]

Display or set the AX25 retransmission  backoff  limit.  Normally
each successive AX25 retransmission is delayed by twice the value
of the previous interval; this is called binary exponential back-
off.   When  the backoff reaches the blimit setting it is held at
that value, which defaults to 30.  To prevent the possibility  of
"congestive  collapse"  on a loaded channel, blimit should be set
at least as high as the number of stations sharing  the  channel.
Note  that this is applicable only on actual AX25 connections; UI
frames will never be retransmitted by the AX25 layer.

3.8.2.  ax25 dest

Display the AX25 destination monitoring database.  Each  callsign
seen in the destination field of an AX25 frame is displayed (most



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recent first), along with the time since it was last  referenced.
The  time  since  the  same  callsign was last seen in the source
field of an AX25 frame on the same interface is  also  shown.  If
the  callsign has never been seen in the source field of a frame,
then this field is left blank. (This indicates that the  destina-
tion is either a multicast address or a "hidden station".)

3.8.3.  ax25 digipeat [on | off]

Display or set the digipeater enable flag.

3.8.4.  ax25 flush

Clear the AX.25 "heard" list (see ax25 heard).

3.8.5.  ax25 heard

Display the AX.25 "heard" list. For each interface that  is  con-
figured  to use AX.25, a list of all callsigns heard through that
interface is shown, along with a count of the number  of  packets
heard  from  each station and the interval, in hr:min:sec format,
since each station was last heard.  The list is sorted  in  most-
recently-heard order.  The local station is included in the list-
ing; the packet count reflects the number of packets transmitted.
This  count will be correct whether or not the modem monitors its
own transmissions.

3.8.6.  ax25 irtt [<milliseconds>]

Display or set the initial value of smoothed round trip  time  to
be  used  when  a new AX25 connection is created. The value is in
milliseconds.  The actual round trip  time  will  be  learned  by
measurement once the connection has been established.

3.8.7.  ax25 kick <axcb>

Force a retransmission on the specified AX.25 control block.

3.8.8.  ax25 maxframe [<count>]

Establish the maximum number of frames that will  be  allowed  to
remain  unacknowledged at one time on new AX.25 connections. This
number cannot be greater than 7.

3.8.9.  ax25 mycall [<call>]

Display or set the local AX.25 address.  The standard  format  is
used (eg. KA9Q-0 or WB6RQN-5).  This command must be given before
any attach commands using AX.25 mode are given.

3.8.10.  ax25 paclen [<size>]

Limit the size of I-fields  on  new  AX.25  connections.   If  IP
datagrams  or  fragments  larger  than this are transmitted, they



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will be transparently fragmented at the AX.25 level,  sent  as  a
series  of  I  frames,  and  reassembled  back into a complete IP
datagram or fragment at the other end of the link.  To  have  any
effect  on  IP  datagrams,  this parameter should be less than or
equal to the MTU of the associated interface.

3.8.11.  ax25 pthresh [<size>]

Display or set the poll threshold to be used for new  AX.25  Ver-
sion  2  connections.  The poll threshold controls retransmission
behavior as follows. If the oldest unacknowledged I-frame size is
less  than  the poll threshold, it will be sent with the poll (P)
bit set if a timeout occurs.  If the oldest unacked I-frame  size
is  equal  to  or  greater  than  the threshold, then a RR or RNR
frame, as appropriate, with the poll bit set will be  sent  if  a
timeout occurs.

The idea behind the poll threshold is that the extra time  needed
to  send  a  "small"  I-frame instead of a supervisory frame when
polling after a timeout is small, and since there's a good chance
the  I-frame  will  have to be sent anyway (i.e., if it were lost
previously) then you might as well send it as the  poll.  But  if
the I-frame is large, send a supervisory (RR/RNR) poll instead to
determine first if retransmitting the  oldest  unacknowledged  I-
frame  is necessary; the timeout might have been caused by a lost
acknowledgement.  This is obviously  a  tradeoff,  so  experiment
with  the  poll  threshold setting. The default is 128 bytes, one
half the default value of paclen.

3.8.12.  ax25 reset <axcb>

Delete the  AX.25  connection  control  block  at  the  specified
address.

3.8.13.  ax25 retry [<count>]

Limit  the  number  of  successive  unsuccessful   retransmission
attempts  on  new  AX.25  connections. If this limit is exceeded,
link re-establishment is attempted. If this  fails  retry  times,
then  the connection is abandoned and all queued data is deleted.
A value of 0 means  "infinity";  the  retry  limit  is  disabled.
retry

3.8.14.  ax25 route

Display the AX.25 routing table that specifies the digipeaters to
be used in reaching a given station.

3.8.14.1.  ax25 route add <target> [digis ... ]

Add an entry to the AX.25 routing table.  An automatic ax25 route
add  is  executed if digipeaters are specified in an AX25 connect
command, or if a connection is received from a remote station via
digipeaters.  Such automatic routing table entries won't override



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locally created entries, however.

3.8.14.2.  ax25 route drop <target>

Drop an entry from the AX.25 routing table.

3.8.15.  ax25 status [<axcb>]

Without an argument, display a one-line  summary  of  each  AX.25
control  block.   If the address of a particular control block is
specified, the contents of that control block are dumped in  more
detail.  Note  that  the  send  queue units are frames, while the
receive queue units are bytes.

3.8.16.  ax25 t3 [<milliseconds>]

Display or set the AX.25 idle "keep alive"  timer.  Value  is  in
milliseconds.

3.8.17.  ax25 version [1 | 2]

Display or set the version of the AX.25 protocol  to  attempt  to
use  on  new connections. The default is 1 (the version that does
not use the poll/final bits).

3.8.18.  ax25 window [<size>]

Set the number of bytes that can be pending on an  AX.25  receive
queue  beyond  which I frames will be answered with RNR (Receiver
Not Ready) responses.  This presently applies only  to  suspended
interactive  AX.25  sessions,  since incoming I-frames containing
network (IP, NET/ROM) packets are  always  processed  immediately
and  are not placed on the receive queue.  However, when an AX.25
connection carries both interactive and network  packet  traffic,
an  RNR  generated because of backlogged interactive traffic will
also stop network packet traffic from being sent.

3.9.  BOOTP

The bootp  client  and  server  are  added  to  KA9Q  to  provide
automatic  configuration capabilities.  With this suite of exten-
sions, a KA9Q host can automatically configure  its  IP  address,
subnet  mask,  broadcast address, host name, the default gateway,
the name servers, and default boot file.   This  simplifies  host
configuration.

The bootp server supports dynamic IP address  assignment.   If  a
bootp  request  is  made  by a host to the server, and the server
doesn't have a static record for the PC making the request, an IP
address  may  be assigned from a list of dynamic addresses.  This
simplifies server configuration, so that machines  don't  require
prior IP address assignment.  This is useful in environments such
as university dormitories, where network service is provided, and
the  computers configurations change frequently.  When the server



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list of free addresses reaches a minimum threshold, it will begin
attempts to reclaim the address.

The bootp client and server code are written according to RFC 951
and 1048.

3.9.1.  bootp  [<net_name>] [silent] [noisy]

Send a request to a bootp server,  and  wait  for  a  reply.   On
receipt of the server reply, the information is used to configure
the host.  If a reply is not received, the command will time out.
Without  arguments,  bootp sends a request to the first interface
in the interface list.

This command requires that there exist a routing entry for the IP
broadcast  address  255.255.255.255  pointing  to the appropriate
interface. If the interface uses ARP, there must also be  an  ARP
entry that maps that address to the appropriate link level broad-
cast address.  For example, if you  have  an  Ethernet  interface
named  "ethernet",  use  the  following commands before the bootp
command:

     route add 255.255.255.255 ethernet

     arp add 255.255.255.255 ether ff:ff:ff:ff:ff:ff

The following bootp subcommands are available:

3.9.1.1.  bootp <net_name>

Send a request over the specified network.

3.9.1.2.  bootp silent

Set bootp so that it will not print the configuration.

3.9.1.3.  bootp noisy

Set bootp so that it will print the configuration.

3.9.2.  bootpd ...

This command starts and stops the bootp server, and sets the con-
figuration  for  the  information it will provide in replies.  If
the file bootptab exists, it will read the file for configuration
information.   On  receipt  of  a  request,  if bootptab has been
changed, the server will reread the file for the  changed  confi-
guration.  The following subcommands are available:

3.9.2.1.  bootpd start

Start the bootp server, reading from the file bootptab for confi-
guration information.




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3.9.2.2.  bootpd stop

Stop the bootp server.

3.9.2.3.  bootpd dns

Print the address of the domain name servers supplied in replies.

3.9.2.4.  bootpd dns <IP addr of domain name server>...

Set the addresses.

3.9.2.5.  bootpd dynip

Print the range and use of the dynamic IP address.

3.9.2.6.  bootpd dynip <net_name> <IP address> <IP address>

Set the range of IP address  to  be  used  for  network  netname.
These address will be supplied to hosts that are not found in the
static record.

3.9.2.7.  bootpd dynip <netname> off

Turn off dynamic ip for network interface netname.

3.9.2.8.  bootpd host

Print the information in the static host table.

3.9.2.9.   bootpd  host   <hostname>    ethernet|ax25   <ethernet
addr>|<ax25 addr> <ip addr> [boot file]

Add a host to the host table.  The LANSTAR packet drivers provide
an Ethernet interface to upper layer applications, so configure a
LANSTAR network as an Ethernet.

3.9.2.10.  bootpd rmhost <hostname>

Remove host <hostname> from the static host tables.

3.9.2.11.  bootpd homedir

Print the default directory for the bootp file name used when the
bootp  file  is not specified in the static host record, and when
dynamic addresses are supplied.  Default is the null string.

3.9.2.12.  bootpd homedir <directory name>

Set the default directory.

3.9.2.13.  bootpd defaultfile

Print the default file for the bootp  file  name  used  when  the



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bootp  file  is not specified in the static host record, and when
dynamic addresses are supplied.  Default is the null string.

3.9.2.14.  bootpd defaultfile <filename>

Set the default file.

3.9.2.15.  bootpd logfile

Print the status of logging to a log file.

3.9.2.16.  bootpd logfile <filename | default> on|off

Sets the file for logging to <filename> or the default, bootplog.
Turn logging to that file on or off.

3.9.2.17.  bootpd logscreen

Print the status of logging to the screen.

3.9.2.18.  bootpd logscreen on|off

Turn logging to the screen on or off.

3.10.  cd [<dirname>]

Change the current working directory, and display  the  new  set-
ting.  Without an argument, cd simply displays the current direc-
tory without change.  The pwd command is an alias for cd.

3.11.  close [<session>]

Close the specified  session;  without  an  argument,  close  the
current  session.   On an AX.25 session, this command initiates a
disconnect.  On a FTP or Telnet session, this command sends a FIN
(i.e.,  initiates a close) on the session's TCP connection.  This
is an alternative to asking the remote server to initiate a close
(QUIT  to  FTP,  or the logout command appropriate for the remote
system in the case of Telnet).  When either FTP  or  Telnet  sees
the  incoming  half  of  a TCP connection close, it automatically
responds by closing the outgoing half of the  connection.   Close
is  more  graceful  than  the  reset  command, in that it is less
likely to leave the remote TCP in a "half-open" state.

3.12.  connect <iface> <callsign> [<digipeater> ... ]

Initiate a "vanilla" AX.25 session to  the  specified  call  sign
using the specified interface. Data sent on this session goes out
in conventional AX.25 packets with no upper layer protocol.   The
de-facto  presentation  standard  format  is  used,  in that each
packet holds one line of text, terminated by a  carriage  return.
A  single  AX.25 connection may be used for terminal-to-terminal,
IP and NET/ROM traffic.  The three types of  data  are  automati-
cally separated by their AX.25 Level 3 Protocol IDs.



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                           - 13 -


Up to 7 optional digipeaters may be given; note that the word via
is  NOT  needed. If digipeaters are specified, they are automati-
cally added to the AX25 routing table as though  the  ax25  route
add command had been given before issuing the connect command.

3.13.  delete <filename>

Delete a filename in the current working directory.

3.14.  detach <iface>

Detach a previously attached interface from the  system.  All  IP
routing  table  entries  referring to this interface are deleted,
and forwarding references by any other interface to  this  inter-
face are removed.

3.15.  dialer <iface> [<dialer-file> [<seconds>  [<tests>  [<hos-
tid>]]]]

Setup an autodialer session  for  the  interface.   Whenever  the
interface  is  idle for the interval in <seconds>, the autodialer
will ping the <hostid>.  If there  is  no  answer  after  <tests>
attempts,  or  the  interface  is otherwise known to be down, the
autodialer will execute the special  commands  contained  in  the
<dialer-file>.

The <dialer-file> may have any valid name, and must be located in
the  configuration  directory  (see the Installion section).  The
commands in the file are  described  in  the  Dialer  Subcommands
chapter.

If the <dialer-file> is missing, any previous dialer command pro-
cess will be removed.  If <seconds> is missing, the <dialer-file>
will be executed  immediately  without  any  further  tests.   If
<tests> is missing, the default is 2.  If <hostid> is missing and
the interface uses the PPP encapsulation, the PPP LCP  echo  will
be used instead.

3.16.  dir [<dirname>]

List the contents of the specified directory on the  console.  If
no  argument is given, the current directory is listed. Note that
this command works by first listing the  directory  into  a  tem-
porary  file,  and  then  creating  a more session to display it.
After this completes, the temporary file is deleted.

3.17.  disconnect [<session #>]

An alias for the close command (for the benefit of AX.25 users).

3.18.  domain ...

These commands control the operation of the Internet Domain  Name
Service (DNS).



                        June 7, 1991





                           - 14 -


3.18.1.  domain addserver <hostid>

Add one or more  domain  name  server(s)  to  the  list  of  name
servers.

3.18.2.  domain dropserver <hostid>

Remove one or more domain name server(s) from the  list  of  name
servers.

3.18.3.  domain listservers

List the currently configured domain  name  servers,  along  with
statistics  on  how  many queries and replies have been exchanged
with each one, response times, etc.

3.18.4.  domain query <hostid>

Send a query to a domain server asking for all  resource  records
associated with this <hostid>, and list the records.

3.18.5.  domain retry [<count>]

Display or set the number of attempts to reach each server on the
list during one call to the resolver.  If this count is exceeded,
a failure indication is returned.  If set to  0,  the  list  will
cycle  forever; this may be useful for unattended operation.  The
default is 3.

3.18.6.  domain suffix [<domain suffix>]

Display or specify the default domain name suffix to be  appended
to  a  host name when it contains no periods. For example, if the
suffix is set to ampr.org and the user enters  telnet  ka9q,  the
domain  resolver  will attempt to find ka9q.ampr.org. If the host
name being sought contains one  or  more  periods,  however,  the
default  suffix  is  NOT applied (eg. telnet foo.bar would NOT be
turned into foo.bar.ampr.org).

3.18.7.  domain trace [on | off]

Display or set the flag controlling the tracing of domain  server
requests  and  responses.  Trace  messages will be seen only if a
domain name being sought is not found in the  local  cache  file,
domain.txt.

3.18.8.  domain cache ...

These commands are used for the use of the resource  record  file
domain.txt, and the local memory cache.

3.18.8.1.  domain cache clean [on | off]

Display or set the  flag  controlling  the  removal  of  resource



                        June 7, 1991





                           - 15 -


records  from  the domain.txt file whose time-to-live has reached
zero.

When  clean  is  off  (the  default),  expired  records  will  be
retained;  if  no replacement can be obtained from another domain
name server, these records will continue to be used.

When clean is on, expired records will be removed from  the  file
whenever any new record is added to the file.

3.18.8.2.  domain cache list

List the current contents of the local memory cache.

3.18.8.3.  domain cache size [<count>]

Display or set the nominal  maximum  size  of  the  local  memory
cache.  The default is 20.

(Note: The cache may be temporarily larger when waiting  for  new
records to be written to the domain.txt file.)

3.18.8.4.  domain cache wait [<seconds>]

Display or set the interval in seconds  to  wait  for  additional
activity before updating the domain.txt file.  The default is 300
seconds (5 minutes).

3.19.  echo [accept | refuse]

Display or set the flag controlling client Telnet's response to a
remote WILL ECHO offer.

The Telnet presentation protocol specifies that in the absence of
a  negotiated  agreement to the contrary, neither end echoes data
received from the other.  In this mode, a Telnet  client  session
echoes  keyboard input locally and nothing is actually sent until
a carriage return is typed. Local line editing is also performed:
backspace  deletes  the  last  character  typed,  while control-U
deletes the entire line.

When communicating from keyboard to keyboard the  standard  local
echo  mode  is  used,  so  the  setting  of this parameter has no
effect. However, many timesharing systems (eg. UNIX) prefer to do
their  own  echoing  of  typed input.  (This makes screen editors
work right, among other things). Such systems send a Telnet  WILL
ECHO  offer immediately upon receiving an incoming Telnet connec-
tion request. If echo accept is in effect, a client  Telnet  ses-
sion  will automatically return a DO ECHO response. In this mode,
local echoing and editing is turned off and each  key  stroke  is
sent immediately (subject to the congestion control algorithms in
TCP).  While this mode is just fine across  an  Ethernet,  it  is
clearly  inefficient  and  painful  across slow paths like packet
radio channels. Specifying echo refuse causes  an  incoming  WILL



                        June 7, 1991





                           - 16 -


ECHO  offer  to  be  answered with a DONT ECHO; the client Telnet
session remains in the local echo mode.  Sessions already in  the
remote  echo  mode are unaffected. (Note: Berkeley Unix has a bug
in that it will still  echo  input  even  after  the  client  has
refused  the  WILL  ECHO offer. To get around this problem, enter
the stty -echo command to the shell once you have logged in.)

3.20.  eol [unix | standard]

Display or set Telnet's end-of-line behavior when in remote  echo
mode.   In  standard  mode, each key is sent as-is. In unix mode,
carriage returns are translated to line feeds.  This  command  is
not  necessary  with  all UNIX systems; use it only when you find
that a particular system responds to line feeds but not  carriage
returns.   Only SunOS release 3.2 seems to exhibit this behavior;
later releases are fixed.

3.21.  escape [<char>]

Display or set the current command-mode escape character in  hex.
(This  command  is  not  provided  on  the IBM-PC; on the PC, the
escape char is always F10.)

3.22.  etherstat

Display 3-Com Ethernet controller statistics (if configured).

3.23.  exit

Exit the net.exe program and return to MS-DOS.

3.24.  finger <user@hostid> [<user@hostid> ...]

Issue a network finger request for user user at host hostid. This
creates  a  client  session  which  may  be interrupted, resumed,
reset, etc, just like a Telnet client session.

3.25.  ftp <hostid>

Open an FTP control channel to  the  specified  remote  host  and
enter  converse  mode  on  the  new  session.  Responses from the
remote server are displayed directly on the screen. See  the  FTP
Subcommands chapter for descriptions of the commands available in
a FTP session.

3.26.  help

Display a brief summary of top-level commands.

3.27.  hop ...

These commands are used to test the connectivity of the network.





                        June 7, 1991





                           - 17 -


3.27.1.  hop check <hostid>

Initiate a hopcheck session to the specified host.  This  uses  a
series  of  UDP  "probe" packets with increasing IP TTL fields to
determine the sequence of gateways in the path to  the  specified
destination. This function is patterned after the UNIX traceroute
facility.

ICMP message tracing should be turned off before this command  is
executed (see the icmp trace command).

3.27.2.  hop maxttl [<hops>]

Display or set the maximum TTL value to be used in hop check ses-
sions.  This effectively bounds the radius of the search.

3.27.3.  hop maxwait [<seconds>]

Display or set the maximum interval that a hopcheck session  will
wait  for  responses at each stage of the trace. The default is 5
seconds.

3.27.4.  hop queries [<count>]

Display or set the number of UDP probes that will be sent at each
stage of the trace. The default is 3.

3.27.5.  hop trace [on | off]

Display or set the flag that controls the display  of  additional
information during a hop check session.

3.28.  hostname [<name>]

Display or set the local host's name. By convention  this  should
be  the  same  as  the host's primary domain name. This string is
used only  in  the  greeting  messages  of  the  various  network
servers; note that it does NOT set the system's IP address.

If <name> is the same as an  <iface>  (see  the  Attach  commands
chapter),  this  command  will search for a CNAME domain resource
record which corresponds to the IP address of the <iface>.

3.29.  hs

Display statistics about the HS high speed HDLC driver  (if  con-
figured and active).

3.30.  icmp ...

These commands are used for the Internet Control Message Protocol
service.





                        June 7, 1991





                           - 18 -


3.30.1.  icmp echo [on | off]

Display or set the flag controlling the asynchronous  display  of
ICMP Echo Reply packets.  This flag must be on for one-shot pings
to work (see the ping command.)

3.30.2.  icmp status

Display statistics about the Internet  Control  Message  Protocol
(ICMP),  including  the number of ICMP messages of each type sent
or received.

3.30.3.  icmp trace [on | off]

Display or set the flag controlling the  display  of  ICMP  error
messages.  These informational messages are generated by Internet
routers in response to routing, protocol or congestion  problems.
This  option  should  be  turned  off  before using the hop check
facility because it relies on ICMP Time  Exceeded  messages,  and
the  asynchronous  display of these messages will be mingled with
hop check command output.

3.31.  ifconfig

Display a list of interfaces, with a short status for each.

3.31.1.  ifconfig <iface>

Display an extended status of the interface.

3.31.2.  ifconfig <iface> broadcast <address>

Set the broadcast address for the interface.  The <address> takes
the  form  of  an  IP  address  with  1's in the host part of the
address.  This is related to the netmask sub-command.   See  also
the arp command.

3.31.3.  ifconfig <iface> encapsulation <name>

Not fully implemented.

3.31.4.  ifconfig <iface> forward <forward-iface>

Set a forwarding interface for multiple channel  interfaces.   To
remove the forward, set <forward-iface> to <iface>.

3.31.5.  ifconfig <iface> ipaddress <hostid>

Set the IP address for this interface.  It is  standard  Internet
practice that each interface has its own address.  For hosts with
only one interface, the interface address is usually the same  as
the host address.  See also the hostname and ip address commands.





                        June 7, 1991





                           - 19 -


3.31.6.  ifconfig <iface> linkaddress <hardware-dependant>

Set the hardware dependant address for this interface.

3.31.7.  ifconfig <iface> mtu <mtu>

Set the MTU for this interface.  See the Setting ... MTU, MSS and
Window chapter for more information.

3.31.8.  ifconfig <iface> netmask <address>

Set the sub-net mask for this interface.  The <address> takes the
form of an IP address with 1's in the network and subnet parts of
the address, and 0's in the host part of the  address.   This  is
related  to  the  broadcast sub-command.  See also the route com-
mand.

3.31.9.  ifconfig <iface> rxbuf <?>

Not yet implemented.

3.32.  ip ...

These commands configure the Internet Protocol (IP) service.

3.32.1.  ip address [<hostid>]

Display or set the default local IP address. This command must be
given before an attach command if it is to be used as the default
IP address for the interface.

3.32.2.  ip rtimer [<seconds>]

Display or set the IP  reassembly  timeout.  The  default  is  30
seconds.

3.32.3.  ip status

Display Internet Protocol (IP) statistics, such as  total  packet
counts and error counters of various types.

3.32.4.  ip ttl [<hops>]

Display or set the time-to-live value placed in each outgoing  IP
datagram.   This  limits  the  number of switch hops the datagram
will be allowed to take. The idea is to bound the lifetime of the
packet  should  it  become  caught in a routing loop, so make the
value slightly larger than the number of hops across the  network
you expect to transit packets.  The default is set at compilation
time to the official recommended value for the Internet.

3.33.  isat [on | off]

Display or set the AT flag.  Currently, there is no sure-fire way



                        June 7, 1991





                           - 20 -


to  determine  the  type of clock-chip being used.  If an AT type
clock is in use, this command will allow measurement of  time  in
milliseconds,  rather than clock ticks (55 milliseconds per clock
tick).

3.33.1.  kick [<session>]

Kick all sockets associated with a session;  if  no  argument  is
given,  kick  the current session.  Performs the same function as
the ax25 kick and tcp kick commands, but is easier to type.

3.34.  log [stop | <filename>]

Display or set the filename for logging server sessions. If  stop
is  given  as  the  argument,  logging is terminated (the servers
themselves are unaffected).  If a file name is given as an  argu-
ment, server session log entries will be appended to it.

3.35.  mbox

Display the status of the mailbox server system (if configured).

3.36.  memory ...

These commands are used to display memory allocation statistics.

3.36.1.  memory free

Display the storage allocator free list. Each entry consists of a
starting address, in hex, and a size, in decimal bytes.

3.36.2.  memory ibuffs

Display or set the number of  buffers  on  the  interrupt  buffer
pool.  The default is 5.

3.36.3.  memory ibufsize

Display or set the size of each buffer on  the  interrupt  buffer
pool.   Since  the  interrupt  buffer pool consists of fixed-size
buffers, the value chosen must be large  enough  to  satisfy  the
needs of the most demanding driver. The default is 2048.

3.36.4.  memory sizes

Display a histogram of storage allocator request sizes. Each his-
togram bin is a binary order of magnitude (i.e., a factor of 2).

3.36.5.  memory status

Display a summary of storage allocator statistics. The first line
shows the base address of the heap, its total size, the amount of
heap memory available in bytes and as a percentage of  the  total
heap  size,  and the amount of memory left over (i.e., not placed



                        June 7, 1991





                           - 21 -


on the heap at startup) and therefore available for shell subcom-
mands.

The second line shows the total number of calls to  allocate  and
free  blocks of memory, the difference of these two values (i.e.,
the number of allocated blocks outstanding), the number of  allo-
cation  requests  that were denied due to lack of memory, and the
number of calls to free() that attempted to free garbage (eg.  by
freeing the same block twice or freeing a garbled pointer).

The third line shows the number of calls to malloc and free  that
occurred  with  interrupts off. In normal situations these values
should be zero.  The fourth line shows statistics for the special
pool of fixed-size buffers used to satisfy requests for memory at
interrupt time. The variables shown are  the  number  of  buffers
currently  in  the  pool,  their size, and the number of requests
that failed due to exhaustion of the pool.

3.37.  mkdir <dirname>

Create a sub-directory in the current working directory.

3.38.  mode <iface> [vc | datagram]

Control the default transmission  mode  on  the  specified  AX.25
interface. In datagram mode, IP packets are encapsulated in AX.25
UI frames and transmitted without any other  link  level  mechan-
isms, such as connections or acknowledgements.

In vc (virtual circuit) mode,  IP  packets  are  encapsulated  in
AX.25  I  frames and are acknowledged at the link level according
to the AX.25 protocol.  Link  level  connections  are  opened  if
necessary.

In both modes, ARP is used to map IP  to  AX.25  addresses.   The
defaults can be overridden with the type-of-service (TOS) bits in
the IP header. Turning on the "reliability" bit causes  I  frames
to  be used, while turning on the "low delay" bit uses UI frames.
(The effect of turning on both bits is undefined and  subject  to
change).

In both modes, IP-level fragmentation is done if the datagram  is
larger  than  the  interface  MTU.  In virtual circuit mode, how-
ever, the resulting datagram (or fragments) is further fragmented
at  the  AX.25  layer  if  it (or they) are still larger than the
AX.25 paclen parameter. In  AX.25  fragmentation,  datagrams  are
broken into several I frames and reassembled at the receiving end
before being passed to IP. This is preferable to IP fragmentation
whenever  possible  because  of decreased overhead (the IP header
isn't repeated in each fragment) and increased robustness (a lost
fragment is immediately retransmitted by the link layer).






                        June 7, 1991





                           - 22 -


3.39.  more <file> [<file> ...]

Display the specified file(s) a screen at a time. To  proceed  to
the  next screen, press the space bar; to cancel the display, hit
the 'q' key.  The more command creates a  session  that  you  can
suspend and resume just like any other session.

3.40.  param <iface> [<param> [value]] ...

Invoke a device-specific control routine.  The following  parame-
ter  names  are  recognized by the parameter command, but not all
are supported by each device type. Most commands deal  only  with
half-duplex packet radio interfaces.

        TxDelay - transmit keyup delay
        Persist - P-persistence setting
        SlotTime - persistence slot time setting
        txTail - transmit done holdup delay
        FullDup - enable/disable full duplex
        Hardware - hardware specific command
        TxMute - experimental transmit mute command
        DTR - control Data Terminal Ready (DTR) signal to modem
        RTS - control Request to Send (RTS) signal to modem
        Speed - set line speed
        EndDelay
        Group
        Idle
        Min
        MaxKey
        Wait
        Down - drop modem control lines
        Up - raise modem control lines
        Return - return a KISS TNC to command mode


Depending on the interface, some parameters can be read  back  by
omitting  a  new  value.  This  is not possible with KISS TNCs as
there are no KISS  commands  for  reading  back  previously  sent
parameters.

On a KISS TNC interface, the param command  generates  and  sends
control  packets  to the TNC.  Data bytes are treated as decimal.
For example, param ax0 txdelay 255   will  set  the  keyup  timer
(type  field  =  1)  on  the  KISS  TNC configured as ax0 to 2.55
seconds (255 x .01 sec).  On all asy interfaces (slip, kiss/ax25,
nrs, ppp) the param <iface> speed command allows the baud rate to
be read or set.

The implementation of this  command  for  the  various  interface
drivers is incomplete and subject to change.

3.41.  ping <hostid> [<length> [<seconds> [<incflag>]]]

Ping (send ICMP Echo Request packets to) the specified  host.  By



                        June 7, 1991





                           - 23 -


default  the data field contains only a small timestamp to aid in
determining round trip time; if the optional length  argument  is
given,  the  appropriate  number of data bytes (consisting of hex
55) are added to the ping packets.

If interval is specified, pings will be repeated indefinitely  at
the  specified  number of seconds; otherwise a single, "one shot"
ping is done.  Responses to one-shot pings appear  asynchronously
on the command screen, while repeated pings create a session that
may be suspended and resumed.  Pinging continues until  the  ses-
sion is manually reset.

The incflag option causes a repeated ping to increment the target
IP  address  for  each  ping;  it  is an experimental feature for
searching blocks of IP addresses for active hosts.

3.42.  ppp ...

These commands are used to  configure  Point  to  Point  Protocol
interfaces.

This implementation of PPP is designed to be as complete as  pos-
sible.   Because  of  this,  the  number of options can be rather
daunting.  However, a typical PPP configuration might include the
following commands:

        attach asy 0x3f8 4 ppp pp0 4096 1500 9600 r
        dial pp0 dialer.pp0 30
        #
        ppp pp0 quick
        ppp pp0 lcp open
        #
        route add default pp0


3.42.1.  ppp <iface>

Display the status of the PPP interface.

3.42.2.  ppp <iface> quick

Quick setup for the PPP link.  By popular demand, this command is
a shortcut for the following commands:

        ppp pp0 ipcp local compress tcp 16 1
        ppp pp0 ipcp open
        ppp pp0 lcp local accm 0
        ppp pp0 lcp local acfc on
        ppp pp0 lcp local pfc on
        ppp pp0 lcp local magic on







                        June 7, 1991





                           - 24 -


3.42.3.  ppp <iface> lcp ...

These commands are used for the LCP [Link Control Protocol]  con-
figuration.

3.42.3.1.  ppp <iface> lcp close

Shutdown the PPP interface.

3.42.3.2.  ppp <iface> lcp local ...

These commands control the configuration of the local side of the
link.   If an option is specified, the parameters will be used as
the initial values in configuration requests.  If not  specified,
that option will not be requested.

For each of these options, the allow parameter  will  permit  the
remote  to  include  that  option  in its response, even when the
option is not included in the request.  By default,  all  options
are allowed.

3.42.3.2.1.  ppp <iface> lcp local accm [ <bitmap> | allow [on  |
off] ]

Display or set the Async Control Character Map.  The  default  is
0xffffffff.

3.42.3.2.2.  ppp <iface> lcp local authenticate [ pap  |  none  |
allow [on | off] ]

Display or set the authentication protocol.  The default is none.

3.42.3.2.3.  ppp <iface> lcp local acfc [ on | off | allow [on  |
off] ]

Display or set the option to compress  the  address  and  control
fields  of the PPP HLDC-like header.  This is generally desirable
for slow asynchronous links, and undesirable for fast or synchro-
nous links.  The default is off.

3.42.3.2.4.  ppp <iface> lcp local pfc [ on | off | allow  [on  |
off] ]

Display or set the option to compress the protocol field  of  the
PPP HLDC-like header.  This is generally desirable for slow asyn-
chronous links, and undesirable for fast  or  synchronous  links.
The default is off.

3.42.3.2.5.  ppp <iface> lcp local magic [ on | off |  <value>  |
allow [on | off] ]

Display or set the initial Magic  Number.   The  default  is  off
(zero).




                        June 7, 1991





                           - 25 -


3.42.3.2.6.  ppp <iface> lcp local mru [ <size>  |  allow  [on  |
off] ]

Display or set the Maximum Receive Unit.  The default is 1500.

3.42.3.2.7.  ppp <iface> lcp local default

Reset the options to their default values.

3.42.3.3.  ppp <iface> lcp listen

Wait for the physical layer to come up, then wait for  configura-
tion negotiation from the remote.  The open command is preferred.

3.42.3.4.  ppp <iface> lcp open

Wait for the physical layer to come up, then initiate  configura-
tion negotiation.

3.42.3.5.  ppp <iface> lcp remote ...

These commands control the configuration of the  remote  side  of
the  link.  The options are identical to those of the local side.
If an option  is  specified,  the  parameters  will  be  used  in
responses  to the remote's configuration requests.  If not speci-
fied, that option will be accepted if it is allowed.

For each of these options, the allow parameter  will  permit  the
remote  to  specify  that option in its request.  By default, all
options are allowed.

3.42.3.6.  ppp <iface> lcp timeout [<seconds>]

Display or set the interval to wait between configuration or ter-
mination attempts.  The default is 3 seconds.

3.42.3.7.  ppp <iface> lcp try ...

These commands are used for the various counters.

3.42.3.7.1.  ppp <iface> lcp try configure [<count>]

Display or set the number of configuration  requests  sent.   The
default is 20.

3.42.3.7.2.  ppp <iface> lcp try failure [<count>]

Display or set the number of bad configuration  requests  allowed
from the remote.  The default is 10.

3.42.3.7.3.  ppp <iface> lcp try terminate [<count>]

Display or set the number of  termination  requests  sent  before
shutdown.  The default is 2.



                        June 7, 1991





                           - 26 -


3.42.4.  ppp <iface> ipcp ...

These commands are used for the IPCP [Internet  Protocol  Control
Protocol] configuration.

The close, listen, open, timeout and try sub-commands are identi-
cal to the LCP (described above).

3.42.4.1.  ppp <iface> ipcp local ...

These commands control the configuration of the local side of the
link.   If an option is specified, the parameters will be used as
the initial values in configuration requests.  If not  specified,
that option will not be requested.

For each of these options, the allow parameter  will  permit  the
remote  to  include  that  option  in its response, even when the
option is not included in the request.  By default,  all  options
are allowed.

3.42.4.1.1.  ppp <iface> ipcp local address [  <hostid>  |  allow
[on | off] ]

Display or set the local address for negotiation purposes.  If an
address of 0 is specified, the other side of the link will supply
the address.  By default, no addresses are negotiated.

3.42.4.1.2.  ppp  <iface>  ipcp  local  compress  [  tcp  <slots>
[<flag>] | none | allow [on | off] ]

Display or set the compression protocol.  The default is none.

The tcp <slots> specifies the  number  of  "conversation"  slots,
which must be 1 to 255.  (This may be limited at compilation time
to a smaller number.) A good choice is in the range 4 to 16.

The tcp <flag> is 0 (don't compress the slot number) or 1 (OK  to
compress  the  slot  number).   KA9Q  can  handle compressed slot
numbers, so the default is 1.

3.42.4.2.  ppp <iface> ipcp remote ...

These commands control the configuration of the  remote  side  of
the  link.  The options are identical to those of the local side.
If an option  is  specified,  the  parameters  will  be  used  in
responses  to the remote's configuration requests.  If not speci-
fied, that option will be accepted if it is allowed.

For each of these options, the allow parameter  will  permit  the
remote  to  specify  that option in its request.  By default, all
options are allowed.






                        June 7, 1991





                           - 27 -


3.42.4.3.  ppp <iface> ipcp pool [<ip-address> [<count>]]

Specify a pool of addresses to be assigned to the  <iface>.   The
<count> is the number of addresses in the pool; the default is 1.

The addresses will be used in rotation.   Overlapping  series  of
addresses may be assigned to more than one <iface>, and conflicts
will be resolved.

3.42.5.  ppp <iface> pap ...

These commands are used for the PAP [Password Authentication Pro-
tocol] configuration.

The timeout  and  try  sub-commands  are  identical  to  the  LCP
(described above).  However, the terminate counter is unused.

3.42.5.1.  ppp <iface> pap user [ <username> [<password>] ]

Display or set the username (the password may  be  set,  but  not
displayed).   When  the username is specified, but no password is
supplied, the ftpusers file is searched for the password.  When a
username/password  is  unknown or rejected, a session will appear
at the console to prompt for a new username/password.

3.42.6.  ppp <iface> trace [<flags>]

Display or set the flags that control the logging of  information
during PPP link configuration.

The flag value is 0 for none, 1 for basic,  and  2  for  general.
Values greater than 2 are usually not compiled, and are described
in the appropriate source files where they are defined.

3.43.  ps

Display all current processes in the system. The  fields  are  as
follows:

PID - Process ID (the address of the process descriptor).

SP - The current value of the process stack pointer.

stksize - The size of the stack allocated to the process.

maxstk - The apparent peak stack  utilization  of  this  process.
This  is  done  in  a  somewhat heuristic fashion, so the numbers
should be treated as  approximate.  If  this  number  reaches  or
exceeds  the  stksize  figure,  the  system  is almost certain to
crash; the net.exe program should be recompiled to give the  pro-
cess a larger allocation when it is started.

event - The event this task is waiting for, if it  is  not  runn-
able.



                        June 7, 1991





                           - 28 -


fl -  Process  status  flags.  There  are  three:  I  (Interrupts
enabled),  W (Waiting for event) and S (Suspended). The I flag is
set whenever a task has executed a pwait() call (wait for  event)
without first disabling hardware interrupts. Only tasks that wait
for hardware interrupt events will turn off this  flag;  this  is
done to avoid critical sections and missed interrupts. The W flag
indicates that the process is waiting for  an  event;  the  event
column will be non-blank. Note that although there may be several
runnable processes at any time (shown in the ps listing as  those
without  the W flag and with blank event fields) only one process
is actually running at any one instant  (The  Refrigerator  Light
Effect  says  that  the ps command is always the one running when
this display is generated.)

3.44.  pwd [<dirname>]

An alias for the cd command.

3.45.  record [off | <filename>]

Append to filename all data  received  on  the  current  session.
Data  sent  on  the current session is also written into the file
except for Telnet sessions in  remote  echo  mode.   The  command
record off stops recording and closes the file.

3.46.  remote [-p <port>] [-k  <key>]  [-a  <kickaddr>]  <hostid>
exit | reset | kick

Send a UDP packet to the specified host commanding it to exit the
net.exe  program,  reset the processor, or force a retransmission
on TCP connections.  For this command to be accepted, the  remote
system  must  be  running  the  remote server and the port number
specified in the remote command must match the port number  given
when  the  server  was started on the remote system.  If the port
numbers do not match, or if the remote server is not  running  on
the  target  system,  the command packet is ignored.  Even if the
command is accepted there is no acknowledgement.

The kick command forces a retransmission timeout on all TCP  con-
nections that the remote node may have with the local node.  If a
connection is idle, a current ACK packet (without data) is  sent.
If  the  -a option is used, connections to the specified host are
kicked instead. No key is required for the kick subcommand.

The exit and reset subcommands are mainly useful  for  restarting
the  net.exe program on a remote unattended system after the con-
figuration file has  been  updated.   The  remote  system  should
invoke the net.exe program automatically upon booting, preferably
in an infinite loop.  For example, under  MS-DOS  the  boot  disk
should contain the following in autoexec.net:

        :loop
        net
        goto :loop



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                           - 29 -


3.47.  remote -s <key>

The exit and reset subcommands of remote require a password.  The
password  is  set on a given system with the -s option, and it is
specified in a command to a remote system with the -k option.  If
no  password  is  set with the -s option, then the exit and reset
subcommands are disabled.

Note that remote is an experimental feature in NOS; it is not yet
supported by any other TCP/IP implementation.

3.48.  rename <oldfilename> <newfilename>

Rename oldfilename to newfilename.

3.49.  reset [<session>]

Reset the specified session; if no argument is given,  reset  the
current  session.  This command should be used with caution since
it does not reliably inform the remote end that the connection no
longer  exists.   (In TCP a reset (RST) message will be automati-
cally generated should the remote TCP send anything after a local
reset  has been done.  In AX.25 the DM message performs a similar
role.  Both are used to get rid of a lingering half-open  connec-
tion after a remote system has crashed.)

3.50.  rip ...

These commands are used for the RIP service.

3.50.1.  rip accept <gateway>

Remove the specified gateway from the RIP filter table,  allowing
future broadcasts from that gateway to be accepted.

3.50.2.  rip add <hostid> <seconds> [<flags>]

Add an entry to the RIP broadcast table.  The  IP  routing  table
will be sent to hostid every interval seconds. If flags is speci-
fied as 1, then "split horizon" processing will be performed  for
this  destination. That is, any IP routing table entries pointing
to the interface that will be used to send this  update  will  be
removed  from  the  update.   If  split horizon processing is not
specified, then all routing table  entries  except  those  marked
"private"  will  be  sent  in  each update.  (Private entries are
never sent in RIP packets).

Triggered updates are always done. That is,  any  change  in  the
routing  table  that causes a previously reachable destination to
become unreachable will trigger an  update  that  advertises  the
destination with metric 15, defined to mean "infinity".

Note that for RIP packets to be  sent  properly  to  a  broadcast
address,  there  must  exist  correct  IP  routing  and ARP table



                        June 7, 1991





                           - 30 -


entries that will first steer the broadcast to the correct inter-
face  and  then place the correct link-level broadcast address in
the link-level destination field.  If  a  standard  IP  broadcast
address  convention  is  used  (eg. 128.96.0.0 or 128.96.255.255)
then chances are you already have the necessary IP routing  table
entry,  but  unusual  subnet  or  cluster-addressed  networks may
require special attention.  However, an arp add command  will  be
required  to translate this address to the appropriate link level
broadcast address.  For example,


arp add 128.96.0.0 ethernet ff:ff:ff:ff:ff:ff


for an Ethernet network, and


arp add 44.255.255.255 ax25 qst-0


for an AX25 packet radio channel.

3.50.3.  rip drop <dest>

Remove an entry from the RIP broadcast table.

3.50.4.  rip merge [on | off]

This flag controls  an  experimental  feature  for  consolidating
redundant  entries  in  the IP routing table. When rip merging is
enabled, the table is scanned after processing each  RIP  update.
An entry is considered redundant if the target(s) it covers would
be routed identically by a less "specific" entry already  in  the
table.  That is, the target address(es) specified by the entry in
question must  also  match  the  target  addresses  of  the  less
specific  entry  and the two entries must have the same interface
and gateway fields. For example, if the routing table contains


Dest            Len Interface    Gateway          Metric  P Timer  Use
1.2.3.4         32  ethernet0    128.96.1.2       1       0 0      0
1.2.3           24  ethernet0    128.96.1.2       1       0 0      0


then the first entry would be deleted as redundant since  packets
sent  to  1.2.3.4  will  still  be routed correctly by the second
entry. Note that the relative metrics of the entries are ignored.

3.50.5.  rip refuse <gateway>

Refuse to accept RIP updates from the specified gateway by adding
the gateway to the RIP filter table. It may be later removed with
the rip accept command.




                        June 7, 1991





                           - 31 -


3.50.6.  rip request <gateway>

Send a RIP Request packet to the specified gateway, causing it to
reply with a RIP Response packet containing its routing table.

3.50.7.  rip status

Display RIP status, including a count of the  number  of  packets
sent  and  received,  the  number  of requests and responses, the
number of unknown RIP packet types, and the number of refused RIP
updates  from  hosts in the filter table. A list of the addresses
and intervals to which periodic RIP updates  are  being  sent  is
also shown, along with the contents of the filter table.

3.50.8.  rip trace [0 | 1 | 2]

This variable controls the tracing of incoming and  outgoing  RIP
packets.   Setting it to 0 disables all RIP tracing. A value of 1
causes changes in the routing table to be displayed, while  pack-
ets  that  cause no changes cause no output. Setting the variable
to 2 produces maximum output, including tracing  of  RIP  packets
that cause no change in the routing table.

3.51.  rmdir <dirname>

Remove a sub-directory from the current working directory.

3.52.  route

With no arguments, route displays the IP routing table.

3.52.1.   route  add  <dest_hostid>[/bits]  |   default   <iface>
[<gateway_hostid> [<metric>]]

This command adds an entry to the routing table. It  requires  at
least  two  more  arguments, the hostid of the target destination
and the name of the interface to  which  its  packets  should  be
sent.   If  the  destination  is  not local, the gateway's hostid
should also be specified. (If the interface is  a  point-to-point
link,  then  gateway_hostid  may be omitted even if the target is
non-local because this  field  is  only  used  to  determine  the
gateway's  link  level  address,  if  any.  If the destination is
directly reachable, gateway_hostid is also unnecessary since  the
destination  address  is  used  to  determine  the interface link
address).

The optional /bits suffix to the destination  host  id  specifies
how  many leading bits in the host id are to be considered signi-
ficant in the routing comparisons.  If  not  specified,  32  bits
(i.e., full significance) is assumed.  With this option, a single
routing table entry may refer to many hosts all sharing a  common
bit  string prefix in their IP addresses. For example, ARPA Class
A, B and C networks would use suffixes of /8, /16 and /24 respec-
tively; the command



                        June 7, 1991





                           - 32 -



route add 44/8 sl0 44.64.0.2


causes any IP addresses beginning with "44" in the first  8  bits
to  be  routed  to  44.64.0.2;  the remaining 24 bits are "don't-
cares".

When an IP address to be routed matches more than  one  entry  in
the  routing  table, the entry with largest bits parameter (i.e.,
the "best" match) is used. This allows individual hosts or blocks
of  hosts  to  be  exceptions to a more general rule for a larger
block of hosts.

The special destination default is used  to  route  datagrams  to
addresses  not matched by any other entries in the routing table;
it is equivalent to specifying a /bits suffix of /0 to any desti-
nation hostid.  Care must be taken with default entries since two
nodes with default entries pointing  at  each  other  will  route
packets to unknown addresses back and forth in a loop until their
time-to-live (TTL) fields expire.  (Routing  loops  for  specific
addresses  can  also be created, but this is less likely to occur
accidentally). The best way to use default routes is to pick  one
node in your network that has the "best" connections to the world
outside your network. Create a spanning tree with  that  node  as
the  root  and have each node install a default route pointing in
the direction of that node, with the exception of the root node.

Here are some examples of the route command:

# Route datagrams to IP address 44.0.0.3 to SLIP line #0.
# No gateway is needed because SLIP is point-to point.
route add 44.0.0.3 sl0

# Route all default traffic to the gateway on the local Ethernet
# with IP address 44.0.0.1
route add default ec0 44.0.0.1

# The local Ethernet has an ARPA Class-C address assignment;
# route all IP addresses beginning with 192.4.8 to it
route add 192.4.8/24 ec0

# The station with IP address 44.0.0.10 is on the local AX.25 channel
route add 44.0.0.10 ax0


3.52.2.  route addprivate <dest hostid>[/bits] | default  <iface>
[<gateway hostid> [<metric>]]

This command is identical to route add except that it also  marks
the  new  entry as private; it will never be included in outgoing
RIP updates.





                        June 7, 1991





                           - 33 -


3.52.3.  route drop <dest hostid>

route drop deletes an entry from the table. If a  packet  arrives
for the deleted address and a default route is in effect, it will
be used.

3.53.  session [<session #>]

Without arguments, displays the list of current sessions, includ-
ing  session  number, remote TCP or AX.25 address and the associ-
ated socket index.  An asterisk (*) is shown next to the  current
session; entering a blank line at this point puts you in converse
mode with that session.  Entering a session number as an argument
to  the  session  command will put you in converse mode with that
session.  If the Telnet server is enabled, the user  is  notified
of  an  incoming  request  and  a session number is automatically
assigned.  The user may then select the session normally to  con-
verse with the remote user as though the session had been locally
initiated.

3.54.  shell

Suspends net.exe and executes a  sub-shell  ("command  processor"
under  MS-DOS).  When the sub-shell exits, net.exe resumes (under
MS-DOS,  enter  the  exit  command).   Background  activity  (FTP
servers, etc) is also suspended while the subshell executes. Note
that this will fail unless there is sufficient unused memory  for
the sub-shell and whatever command the user tries to run.

3.55.  smtp ...

These commands control the operation of the Simple Mail  Transfer
Protocol (that is, mail).

3.55.1.  smtp gateway [<hostid>]

Displays or sets the host to be used as a "smart" mail relay. Any
mail sent to a host not in the host table will instead be sent to
the gateway for forwarding.

3.55.2.  smtp kick

Run through the outgoing mail queue and attempt  to  deliver  any
pending  mail.   This  command allows the user to "kick" the mail
system manually.  Normally, this command is periodically  invoked
by a timer whenever net.exe is running.

3.55.3.  smtp maxclients [<count>]

Displays or sets the maximum number of simultaneous outgoing SMTP
sessions  that  will  be allowed. The default is 10; reduce it if
network congestion is a problem.





                        June 7, 1991





                           - 34 -


3.55.4.  smtp timer [<seconds>]

Displays or sets the interval between "kicks" (scans) of the out-
bound mail queue. For example, smtp timer 600 will cause the sys-
tem to check for outgoing mail every 10 minutes  and  attempt  to
deliver  anything  it  finds,  subject of course to the smtp max-
clients limit. Setting a value of zero  disables  queue  scanning
altogether,  note that this is the default!  This value is recom-
mended for stand alone IP gateways that never handle mail,  since
it saves wear and tear on the floppy disk drive.

3.55.5.  smtp trace [<value>]

Displays or sets the trace flag in the SMTP client, allowing  you
to  watch  SMTP's  conversations  as it delivers mail.  Zero (the
default) disables tracing.

3.56.  socket [<socket #>]

Without an argument, displays all active  sockets,  giving  their
index  and  type,  the address of the associated protocol control
block and the and owner process ID and name. If the index  to  an
active socket is supplied, the status display for the appropriate
protocol is called.  For example, if the socket refers to  a  TCP
connection, the display will be that given by the tcp status com-
mand with the protocol control block address.

3.57.  start ax25 | discard | echo | ftp | netrom | remote | smtp
| telnet | ttylink

Start the specified Internet server, allowing  remote  connection
requests.

3.58.  stop ax25 | discard | echo | ftp | netrom | remote |  smtp
| telnet | ttylink

Stop the specified Internet server, rejecting any further  remote
connect  requests.  Existing  connections are allowed to complete
normally.

3.59.  tcp ...

These commands are used for  the  Transmission  Control  Protocol
service.

3.59.1.  tcp irtt [<milliseconds>]

Display or set the initial round  trip  time  estimate,  in  mil-
liseconds,  to  be  used  for  new TCP connections until they can
measure and adapt to the actual value.  The default is 5000  mil-
liseconds  (5 seconds).  Increasing this when operating over slow
channels will avoid the flurry of retransmissions that would oth-
erwise occur as the smoothed estimate settles down at the correct
value. Note that this command should be given before servers  are



                        June 7, 1991





                           - 35 -


started in order for it to have effect on incoming connections.

TCP also caches measured round trip  times  and  mean  deviations
(MDEV)  for  current  and recent destinations. Whenever a new TCP
connection is opened, the system first looks in  this  cache.  If
the  destination  is  found,  the cached IRTT and MDEV values are
used. If not, the default IRTT value  mentioned  above  is  used,
along  with a MDEV of 0.  This feature is fully automatic, and it
can improve performance greatly when a series of connections  are
opened  and  closed  to  a given destination (eg. a series of FTP
file transfers or directory listings).

3.59.2.  tcp kick <tcb_addr>

If there is unacknowledged data on the send queue of  the  speci-
fied TCB, this command forces an immediate retransmission.

3.59.3.  tcp mss [<size>]

Display or set the TCP Maximum Segment Size in bytes that will be
sent  on  all  outgoing TCP connect request (SYN segments).  This
tells the remote end the size of the largest segment (packet)  it
may  send. Changing MSS affects only future connections; existing
connections are unaffected.

3.59.4.  tcp reset <tcb_addr>

Deletes the TCP control block at the specified address.

3.59.5.  tcp rtt <tcb_addr> <rtt> <mdev>

Replaces the automatically computed  round  trip  time  and  mean
deviation  values  in  the  specified TCB with new values in mil-
liseconds.  This command is useful to speed up  recovery  from  a
series  of  lost packets since it provides a manual bypass around
the normal backoff retransmission timing mechanisms.

3.59.6.  tcp status [<tcb_addr>]

Without arguments, displays several TCP-level statistics, plus  a
summary  of  all existing TCP connections, including TCB address,
send and receive queue sizes, local and remote sockets, and  con-
nection  state. If tcb_addr is specified, a more detailed dump of
the specified  TCB  is  generated,  including  send  and  receive
sequence numbers and timer information.

3.59.7.  tcp window [<size>]

Displays or sets the default receive window size in bytes  to  be
used  by  TCP when creating new connections. Existing connections
are unaffected.






                        June 7, 1991





                           - 36 -


3.60.  telnet <hostid>

Creates a Telnet session to the specified host  and  enters  con-
verse mode.

3.61.  tip <iface>

Creates a tip session that connects to the specified interface in
"dumb  terminal"  mode.   The  interface  must  have already been
attached  with  the  attach  command.   Any  packet  traffic  (IP
datagrams, etc) routed to the interface while this session exists
will be discarded.  To close a tip session, use  the  reset  com-
mand. It will then revert to normal slip, nrs or kiss mode opera-
tion.

This feature is primarily useful for manually  establishing  SLIP
connections.   At  present,  only the built-in "com" ports can be
used with this command.

3.62.  trace [<iface> [off | <btio> [<tracefile>]]]

Controls packet tracing by the interface drivers.  Specific  bits
enable tracing of the various interfaces and the amount of infor-
mation produced.  Tracing is controlled on a per-interface basis;
without  arguments,  trace gives a list of all defined interfaces
and their tracing status.  Output can  be  limited  to  a  single
interface  by  specifying it, and the control flags can be change
by specifying them as well. The flags are given as a  hexadecimal
number which is interpreted as follows:

    O - Enable tracing of output packets if 1, disable if 0
    I - Enable tracing of input packets if 1, disable if 0
    T - Controls type of tracing:
        0 - Protocol headers are decoded, but data is not displayed
        1 - Protocol headers are decoded, and data (but not the
            headers themselves) are displayed as ASCII characters,
            64 characters/line. Unprintable characters are displayed
            as periods.
        2 - Protocol headers are decoded, and the entire packet
            (headers AND data) is also displayed in hexadecimal
            and ASCII, 16 characters per line.
    B - Broadcast filter flag. If set, only packets specifically addressed
        to this node will be traced; broadcast packets will not be displayed.

If tracefile is not specified, tracing will be to the console.

3.63.  udp status

Displays the status of all UDP receive queues.

3.64.  upload [<filename>]

Opens filename and sends it on the current session as  though  it
were typed on the terminal.



                        June 7, 1991





                           - 37 -


3.65.  watch

Displays the current software stopwatch values, with min and  max
readings  for  each. This facility allows a programmer to measure
the execution time of critical sections of code with  microsecond
resolution.   This  command  is supported only on the IBM PC, and
the meaning of each stopwatch value depends on  where  the  calls
have  been  inserted  for test purposes; the distribution copy of
net.exe usually has no stopwatch calls.

3.66.  ?

Same as the help command.

4.  Attach Commands

This chapter details the attach commands for the various hardware
interface  drivers.  Not  all  of these drivers may be configured
into every net.exe binary; a list of the available types  may  be
obtained by entering the command attach ?.

Some parameters are accepted by several drivers. They are:

4.0.1.  <bufsize>

For asynchronous devices (eg. COM ports operating in SLIP or  NRS
mode)  this  parameter  specifies the size of the receiver's ring
buffer.  It should be large enough to hold incoming data at  full
line  speed  for  the longest time that the system may be busy in
MS-DOS or the BIOS doing a slow I/O operation (eg.  to  a  floppy
disk). A kilobyte is usually more than sufficient.

For synchronous devices (eg. the scc, hs, pc100,  hapn  and  drsi
interfaces  operating in HDLC mode), the bufsize parameter speci-
fies the largest packet that may be received  on  the  interface.
This should be set by mutual agreement among stations sharing the
channel. For standard AX.25 with a maximum I-frame data  size  of
256  bytes, a value of 325 should provide an adequate safety mar-
gin. On higher speed channels (eg. 56kb/s) larger values (eg.  2K
bytes)  will provide much better performance and allow full-sized
Ethernet packets to be carried without fragmentation.

4.0.2.  <ioaddr>

The base address of the interface's control registers, in hex.

4.0.3.  <vector>

The interface's hardware interrupt (IRQ) vector, in hex.

4.0.4.  <iface>

The name (an arbitrary character string) to be assigned  to  this
interface.  It  is used to refer to the interface in ifconfig and



                        June 7, 1991





                           - 38 -


route commands and in trace output.

4.0.5.  <mtu>

The Maximum Transmission Unit size, in bytes.   Datagrams  larger
than  this  limit will be fragmented at the IP layer into smaller
pieces. For AX.25 UI frames, this limits the size of the informa-
tion field.  For AX.25 I frames, however, the ax25 paclen parame-
ter is also relevant.  If  the  datagram  or  fragment  is  still
larger  than paclen, it is also fragmented at the AX.25 level (as
opposed to the IP level)  before  transmission.   (See  the  ax25
paclen command for further information).

4.0.6.  <speed>

The speed in bits per second (eg. 2400).

4.1.  attach 3c500 <ioaddr> <vector> arpa  <iface>  <qlen>  <mtu>
[<ip_addr>]

Attach a 3Com 3C501 Ethernet  interface.   qlen  is  the  maximum
allowable transmit queue length.  If the ip_addr parameter is not
given, the value associated with a prior ip address command  will
be used.

The use of this driver is not recommended; use the packet  driver
interface with the loadable 3C501 packet driver instead.

4.2.  attach asy <ioaddr> <vector>  ax25  |  nrs  |  ppp  |  slip
<iface> <bufsize> <mtu> <speed> [<crv>]

Attach a standard PC "com port" (asynchronous serial port), using
the  National 8250 or 16550A chip.  Standard values on the IBM PC
and clones for ioaddr and vector are 0x3f8 and 4  for  COM1,  and
0x2f8 and 3 for COM2.  If the port uses a 16550A chip, it will be
detected automatically and the FIFOs enabled.

4.2.1.  ax25

Similar to slip, except that an AX.25 header and a KISS TNC  con-
trol  header  are  added to the front of the datagram before SLIP
encoding.  Either UI (connectionless) or I  (connection-oriented)
AX.25 frames can be used; see the mode command for details.

4.2.2.  nrs

Use the NET/ROM asynchronous framing technique for  communication
with a local NET/ROM TNC.

4.2.3.  ppp

Point-to-Point-Protocol.  Encapsulates datagrams in an  HDLC-like
frame.   This  is a new Internet standard for point-to-point com-
munication, compatible with CCITT standards.



                        June 7, 1991





                           - 39 -


4.2.4.  slip

Serial  Line  Internet  Protocol.   Encapsulates   IP   datagrams
directly in SLIP frames without a link header. This is for opera-
tion on point-to-point lines and is compatible with  4.2BSD  UNIX
SLIP.

4.2.5.  <crv>

The optional flags are a string of characters  "crv":  c  enables
RTS/CTS  detection, r enables RLSD (Carrier Detect) physical line
sensing, v enables Van Jacobson TCP/IP Header Compression, and is
valid only for SLIP.

4.3.  attach drsi <ioaddr> <vector> ax25 <iface> <bufsize>  <mtu>
<ch_a_speed> <ch_b_speed>

N6TTO driver for the Digital Radio Systems PCPA 8530 card.  Since
there are two channels on the board, two interfaces are attached.
They will be named iface with 'a' and 'b' appended.   bufsize  is
the  receiver  buffer  size  in bytes; it must be larger than the
largest frame to be received.  ch_a_speed and ch_b_speed are  the
speeds, in bits/sec, for the A and B channels, respectively.

4.4.  attach eagle <ioaddr> <vector> ax25 <iface> <bufsize> <mtu>
<speed>

WA3CVG/NG6Q driver for the Eagle Computer card (Zilog 8530).

4.5.  attach hapn <ioaddr> <vector> ax25 <iface> <bufsize>  <mtu>
csma | full

KE3Z driver for  the  Hamilton  Amateur  Packet  Network  adapter
(Intel  8273).   The  csma | full parameter specifies whether the
port should operate in carrier sense multiple access (CSMA)  mode
or in full duplex.

4.6.  attach hs <ioaddr> <vector> ax25  <iface>  <bufsize>  <mtu>
<keyup_delay> <p>

Attach a DRSI PCPA or Eagle Computer interface card using a  spe-
cial  "high speed" 8530 driver.  This driver uses busy-wait loops
to send and receive each byte instead of  interrupts,  making  it
usable  with  high speed modems (such as the WA4DSY 56kb/s modem)
on slow systems.  This does have the side  effect  of  "freezing"
the  system whenever the modem transmitter or receiver is active.
This driver can operate only in CSMA mode, and it is  recommended
that  no  other interfaces requiring small interrupt latencies be
attached to the same machine.

The keyup_delay parameter specifies the transmitter  keyup  delay
in  milliseconds.  The  p  value  specifies  the transmitter per-
sistence value in the range 1-255; the corresponding slot time is
fixed at one hardware clock tick, about 55 ms on the PC.



                        June 7, 1991





                           - 40 -


As with the other 8530 drivers, this driver actually attaches two
interfaces, one for each 8530 channel.

4.7.  attach packet <intvec> <iface> <txqlen> <mtu>

Attach a  separate  software  "packet  driver"  meeting  the  FTP
Software,  Inc, Software Packet Driver specification.  The driver
must have already been installed as a TSR (e.g., by invocation in
autoexec.bat).   Packet  drivers  in  the Ethernet, ARCNET, SLIP,
SLFP, and KISS/AX25 classes are supported.

intvec is the software interrupt vector used for communication to
the  packet  driver,  and txqlen is the maximum number of packets
that will be allowed on the transmit queue.

4.8.  attach  pc100  <ioaddr>  <vector>  ax25  <iface>  <bufsize>
<speed>

Driver for the PACCOMM PC-100  (Zilog  8530)  card.   Only  AX.25
operation is supported.

4.9.  attach scc <devices> init <addr>  <spacing>  <Aoff>  <Boff>
<Dataoff> <intack> <vec> [p|r]<clock> [<hdwe>] [<param>]

PE1CHL driver to initialize a generic SCC (8530) interface  board
prior to actually attaching it. The parameters are as follows:

4.9.1.  <devices>

The number of SCC chips to support.

4.9.2.  <addr>

The base address of the first SCC chip (hex).

4.9.3.  <spacing>

The spacing between the SCC chip base addresses.

4.9.4.  <Aoff>

The offset from a chip's base address to its  channel  A  control
register.

4.9.5.  <Boff>

The offset from a chip's base address to its  channel  B  control
register.

4.9.6.  <Dataoff>

The offset from each  channel's  control  register  to  its  data
register.




                        June 7, 1991





                           - 41 -


4.9.7.  <intack>

The address of the INTACK/Read Vector port. If none, specify 0 to
read from RR3A/RR2B.

4.9.8.  <vec>

The CPU interrupt vector for all connected SCCs.

4.9.9.  <clock>

The clock frequency (PCLK/RTxC) of all  SCCs  in  hertz.   Prefix
with 'p' for PCLK, 'r' for RTxC clock (for baudrate gen).

4.9.10.  <hdwe>

Optional hardware type. The following values are  currently  sup-
ported:  1  -  Eagle card, 2 - PACCOMM PC-100, 4 - PRIMUS-PC card
(DG9BL), 8 - DRSI PCPA card.

4.9.11.  <param>

Optional extra parameter. At present, this is used only with  the
PC-100  and PRIMUS-PC cards to set the modem mode. The value 0x22
is used with the PC-100 and 0x2 is used with the PRIMUS-PC card.

The attach scc ... init command must be given before  the  inter-
faces are actually attached with the following command.

4.10.  attach scc <chan> slip | kiss | nrs | ax25  <iface>  <mtu>
<speed> <bufsize> [<call>]

Attach an initialized SCC port to the system. The parameters  are
as follows:

4.10.1.  <chan>

The SCC channel number to attach, 0 or 1 for the first  chip's  A
or B port, 2 or 3 for the second chip's A or B port, etc.

4.10.2.  slip | kiss | nrs | ax25

The operating mode of the  interface.  slip,  kiss  and  nrs  all
operate   the   port  hardware  in  asynchronous  mode;  slip  is
Internet-standard serial line IP mode, kiss generates SLIP frames
containing  KISS  TNC  commands  and  AX.25  packets and nrs uses
NET/ROM local serial link framing conventions  to  carry  NET/ROM
packets.  Selecting ax25 mode puts the interface into synchronous
HDLC mode that is suitable for direct connection to a half duplex
radio modem.

4.10.3.  <speed>

The interface speed in bits per second (eg. 1200).   Prefix  with



                        June 7, 1991





                           - 42 -


'd'  when  an  external  divider  is available to generate the TX
clock. When the clock source is PCLK, this can be a  /32  divider
between  TRxC  and  RTxC.  When the clock is at RTxC, the TX rate
must be supplied at TRxC. This is needed  only  for  full  duplex
synchronous  operation.  When  this  arg  is  given as 'ext', the
transmit and receive clocks are external, and the  internal  baud
rate generator (BRG) and digital phase locked loop (DPLL) are not
used.

4.11.  Attach Examples

Here are some examples of the attach command:


# Attach a 3Com Ethernet controller using the standard 3Com address and
# vector (i.e., as it comes out of the box) to use ARPA-standard encapsulation.
# The receive queue is limited to 5 packets, and outgoing packets larger
# than 1500 bytes will be fragmented
attach 3c500 0x300 3 arpa ec0 5 1500

# Attach the PC asynch card normally known as "com1" (the first controller)
# to operate in point-to-point slip mode at 9600 baud, calling it "sl0".
# A 1024 byte receiver ring buffer is allocated. Outgoing packets larger
# than 256 bytes are fragmented.
attach asy 0x3f8 4 slip sl0 1024 256 9600

# Attach the secondary PC asynch card ("com2") to operate in AX.25 mode
# with an MTU of 576 bytes at 9600 baud with a KISS TNC, calling it "ax0".
# By default, IP datagrams are sent in UI frames
attach asy 0x2f8 3 ax25 ax0 1024 576 9600

# Attach the packet driver loaded at interrupt 0x7e
# The packet driver is for an Ethernet interface
attach packet 0x7e ethernet 8 1500



5.  FTP Subcommands

During converse mode with an FTP server, everything typed on  the
console  is  first  examined to see if it is a locally-known com-
mand. If not, the line is passed intact to the remote  server  on
the control channel. If it is one of the following commands, how-
ever, it is executed locally. (Note that this generally  involves
other  commands  being  sent  to the remote server on the control
channel.)

5.1.  dir [<file> | <directory> [<local file>]]

Without arguments, dir requests that a full directory listing  of
the  remote  server's  current directory be sent to the terminal.
If one argument is given, this is passed along in the  LIST  com-
mand;  this  can be a specific file or subdirectory that is mean-
ingful to the remote file system. If two arguments are given, the



                        June 7, 1991





                           - 43 -


second  is taken as the local file into which the directory list-
ing should be put (instead of being sent to  the  console).   The
PORT command is used before the LIST command is sent.

5.2.  get <remote file> [<local file>]

Asks the remote server to send the file specified  in  the  first
argument.  The second argument, if given, will be the name of the
file on the local machine; otherwise it will have the  same  name
as on the remote machine.  The PORT and RETR commands are sent on
the control channel.

5.3.  hash

A synonym for the verbose 3 command.

5.4.  ls [<file> | <directory> [<local file>]]

ls is identical to the dir command except that the "NLST" command
is sent to the server instead of the "LIST" command. This results
in an abbreviated directory listing, i.e., one showing  only  the
file names themselves without any other information.

5.5.  mget <file> [<file> ...]

Fetch a collection of files  from  the  server.  File  names  may
include  wild  card  characters;  they  will  be  interpreted and
expanded into a list of files by the remote system using the NLST
command.  The  files  will have the same name on the local system
that they had on the server.

5.6.  mkdir <remote directory>

Creates a directory on the remote machine.

5.7.  mput <file> [<file> ...]

Send a collection of files to the server. File names may  include
wild  card  characters; they will be expanded locally into a list
of files to be sent. The files will have the  same  name  on  the
server as on the local system.

5.8.  put <local file> [<remote file>]

Asks the remote server to accept data, creating the file named in
the  first  argument.  The second argument, if given, will be the
name of the file on the remote machine; otherwise  it  will  have
the  same  name  as on the local machine.  The PORT and STOR com-
mands are sent on the control channel.

5.9.  rmdir <remote directory>

Deletes a directory on the remote machine.




                        June 7, 1991





                           - 44 -


5.10.  type [a | i | l <bytesize>]

Tells both the local client and remote server the  type  of  file
that is to be transferred.  The default is 'a', which means ASCII
(i.e., a text file).  Type 'i' means  image,  i.e.,  binary.   In
ASCII  mode,  files  are  sent as varying length lines of text in
ASCII separated by cr/lf sequences; in IMAGE mode, files are sent
exactly  as they appear in the file system.  ASCII mode should be
used whenever transferring text between dissimilar  systems  (eg.
UNIX  and  MS-DOS)  because of their different end-of-line and/or
end-of-file conventions.   When  exchanging  text  files  between
machines  of  the same type, either mode will work but IMAGE mode
is usually faster.  Naturally, when exchanging raw  binary  files
(executables,  compressed archives, etc) IMAGE mode must be used.
Type 'l' (logical byte size) is used when exchanging binary files
with  remote servers having oddball word sizes (eg. DECSYSTEM-10s
and 20s).  Locally it works exactly like IMAGE,  except  that  it
notifies  the  remote system how large the byte size is. bytesize
is typically 8.  The type command sets the  local  transfer  mode
and generates the TYPE command on the control channel.

5.11.  verbose [0 | 1 | 2 | 3]

Set or display the level of message  output  in  file  transfers.
Verbose 0 gives the least output, and verbose 3 the most, as fol-
lows:

0 - Display error messages only.
1 - Display error messages plus a one-line summary after each transfer
    giving the name of the file, its size, and the transfer time and rate.
2 - Display error and summary messages plus the progress messages generated
    by the remote FTP server. (This setting is the default.)
3 - Display all messages. In addition, a "hash mark" (#) is displayed for
    every 1,000 bytes sent or received.

If a command is sent to the  remote  server  because  it  is  not
recognized  locally, the response is always displayed, regardless
of the setting of verbose.  This is necessary for  commands  like
pwd (display working directory), which would otherwise produce no
message at all if verbose were set to 0 or 1.

6.  Dialer Subcommands

Each dialer command may (should) have a  different  dialer  file.
The  file resides in the configuration directory, as specified in
the Installation section (see chapter 1).  A typical dialer  file
might be:










                        June 7, 1991





                           - 45 -



        # Set the speed, and toggle DTR to ensure modem is in command mode.
        control down
        wait 3000
        speed 2400
        control up
        wait 3000
        # Dial, and wait for connection
        send "atdt555-1212"
        wait 45000 "CONNECT " speed
        wait 2000
        # PAD specific initialization
        send ""
        wait 15000 "Terminal ="
        send "ppp"
        wait 10000 "


6.0.1.  control down | up

Control asy interface.  The down option drops DTR and  RTS.   The
up option asserts DTR and RTS.

6.0.2.  send "string" [<milliseconds>]

This dialer command will write the specified string to the inter-
face.   The  string  quote marks are required, and the string may
not contain embedded control characters.  However, the standard C
string escape sequences are recognized (\0 should not be used).

There may be a wait of  <milliseconds>  between  each  character.
This  is  used  when  the dialer cannot process a string at modem
speeds.

6.0.3.  speed [ 9600 | 4800 | 2400 | 1200 | 300 ]

This dialer command will set the speed of the interface to one of
the available speeds.  If the speed is missing, the speed will be
displayed in the dialer session window.

6.0.4.  wait <milliseconds> [ "test string" ] [ speed ]

If only the time is specified, the dialer pauses for the  desired
number of milliseconds.

Otherwise, the dialer reads until the test string is detected  on
the  interface.  If the string is not detected within the desired
time, the autodialer will reset.   The  string  quote  marks  are
required, and the string may not contain embedded control charac-
ters.  However, the standard C string escape sequences are recog-
nized (\0 should not be used).

Finally, if the speed parameter is  specified,  the  dialer  will
continue  to  read characters until a non-digit is detected.  The



                        June 7, 1991





                           - 46 -


string read is converted to an  integer,  and  used  to  set  the
interface  speed.   If  the  trailing  non-digit  is not detected
within the desired time, or the integer  value  is  not  a  valid
speed,  the  autodialer  will reset.  The speed feature is useful
for reading back the CONNECT <speed> message generated by  Hayes-
compatible modems.

7.  The /ftpusers File

Since MS-DOS is a single-user operating system (some might say it
is  a glorified bootstrap loader), it provides no access control;
all files can be read, written or deleted by the local user.   It
is  usually  undesirable  to give such open access to a system to
remote network users.  Net.exe therefore provides its own  access
control mechanisms.

The file /ftpusers controls remote FTP and mailbox  access.   The
FTP  default  is  no access; if this file does not exist, the FTP
server will be unusable.  A remote user must first  "log  in"  to
the  system  with the USER and PASS commands, giving a valid name
and password listed in /ftpusers, before he or she  can  transfer
files.

Each entry in /ftpusers consists of a single line of the form

username password /path permissions


There must be exactly four fields, and there must be exactly  one
space  between  each field.  Comments may be added after the last
field. Comment lines begin with '#' in column one.

username is the user's login name.

password is the required password.  Note that this  is  in  plain
text;  therefore  it is not a good idea to give general read per-
mission to the root directory.   A  password  of  '*'  (a  single
asterisk) means that any password is acceptable.

/path is the allowable prefix on accessible  files.   Before  any
file  or directory operation, the current directory and the user-
specified file name are joined to form an absolute path  name  in
"canonical"  form  (i.e.,  a full path name starting at the root,
with "./" and "../" references, as well as redundant /'s,  recog-
nized and removed). The result MUST begin with the allowable path
prefix; if not, the operation is denied.  This field must  always
begin with a "/", i.e., at the root directory.

permissions is a decimal number  granting  permission  for  read,
create  and write operations.  If the low order bit (0x1) is set,
the user is allowed to read a file subject to the path name  pre-
fix  restriction.   If  the  next  bit  (0x2) is set, the user is
allowed to create a new file if it does not overwrite an existing
file.   If  the  third  bit  (0x4) is set, the user is allowed to



                        June 7, 1991





                           - 47 -


write a file even if it overwrites an existing file, and in addi-
tion he may delete files.  Again, all operations are allowed sub-
ject to the path name prefix  restrictions.  Permissions  may  be
combined  by  adding  bits,  for example, 0x3 (= 0x2 + 0x1) means
that the user is  given  read  and  create  permission,  but  not
overwrite/delete permission.

For example, suppose /ftpusers on machine  pc.ka9q.ampr.org  con-
tains the line

friendly test /testdir 7


A session using this account would look like this:

net> ftp pc.ka9q.ampr.org
Resolving pc.ka9q.ampr.org... Trying 128.96.160.1...
FTP session 1 connected to pc.ka9q.ampr.org
220 pc.ka9q.ampr.org FTP version 900418 ready at Mon May 7 16:27:18 1990
Enter user name: friendly
331 Enter PASS command
Password: test [not echoed]
230 Logged in
ftp>


The user now has read, write, overwrite and delete privileges for
any file under /testdir; he may not access any other files.

Here are some more sample entries in /ftpusers:

karn foobar / 7         # User "karn" with password "foobar" may read,
                        # write, overwrite and delete any file on the
                        # system.

guest bletch /g/bogus 3 # User "guest" with password "bletch" may read
                        # any file under /g/bogus and its subdirectories,
                        # and may create a new file as long as it does
                        # not overwrite an existing file. He may NOT
                        # delete any files.

anonymous * /public 1   # User "anonymous" (any password) may read files
                        # under /public and its subdirectories; he may
                        # not create, overwrite or delete any files.


This last entry is the standard convention for keeping a  reposi-
tory  of public files; in particular, the username "anonymous" is
an established ARPA convention.

8.  The domain.txt File

Net.exe translates domain names (eg.  "pc.ka9q.ampr.org")  to  IP
addresses  (eg.  128.96.160.3)  through  the  use  of an Internet



                        June 7, 1991





                           - 48 -


Domain Name resolver and a local "cache" file, domain.txt.  When-
ever  the  user  specifies  a  domain  name,  the  local cache is
searched for the desired entry.  If it is present, it is used; if
not,  and  if domain name server(s) have been configured, a query
is sent over the network to the current server.   If  the  server
responds,  the  answer is added to the domain.txt file for future
use.  If the server does not respond, any additional  servers  on
the  list  are tried in a round-robin fashion until one responds,
or the retry limit is reached (see the domain retry command).  If
domain.txt  does  not  contain the desired entry and there are no
configured domain name  servers,  then  the  request  immediately
fails.

If a domain name server is available, and if  all  references  to
host-ids  in  your  /autoexec.net  file are in IP address format,
then it is possible to start with a completely  empty  domain.txt
file and have net.exe build it for you.  However, you may wish to
add your own entries to domain.txt, either because you prefer  to
use symbolic domain names in your /autoexec.net file or you don't
have access to a domain server and you need to create entries for
all of the hosts you may wish to access.

Each entry takes one line, and the fields are  separated  by  any
combination of tabs or spaces.  For example:

pc.ka9q.ampr.org.       IN      A       128.96.160.3

IN is the class of the record.  It means Internet, and it will be
found  in all entries.  A is the type of the record, and it means
that this is an address  record.   Domain  name  pc.ka9q.ampr.org
therefore has Internet address 128.96.160.3.

Another possible entry is the CNAME (Canonical Name) record.  For
example:

ka9q.ampr.org.          IN      CNAME   pc.ka9q.ampr.org.

This says that domain name "ka9q.ampr.org" is actually  an  alias
for   the   system  with  (primary,  or  canonical)  domain  name
"pc.ka9q.ampr.org." When a domain name having a CNAME  record  is
given  to net.exe, the system automatically follows the reference
to the canonical name and returns the IP address associated  with
that entry.

Entries added automatically by net.exe will  have  an  additional
field  between  the  domain  name  and the class (IN) field.  For
example:

pc.ka9q.ampr.org.       3600    IN      A       128.96.160.3

This is the time-to-live value, in seconds, associated  with  the
record  received from the server. Clients (such as net.exe) cach-
ing these records are supposed to delete them after the  time-to-
live  interval has expired, allowing for the possibility that the



                        June 7, 1991





                           - 49 -


information in the record may become out of date.

This implementation of net.exe will decrement the  TTL  to  zero,
but will not delete the record unless the "clean" flag is on (see
the domain cache clean command).  When a  remote  server  is  not
available, the old entry will be used.

When the TTL value is missing (as in  the  examples  above),  the
record  will  never  expire,  and must be managed by hand.  Since
domain.txt is a plain text file, it may be easily edited  by  the
user to add, change or delete records.

Additional types of records include MX (mail exchanger), NS (name
server)  and  SOA  (start  of authority) may appear in domain.txt
from remote server  responses.  Only  MX  is  currently  used  by
net.exe  (in  the  mailbox).  The  others are retained for future
development (such as the incorporation of a smarter resolver or a
full-blown domain name server).

9.  Setting Bufsize, Paclen, Maxframe, MTU, MSS and Window

Many net.exe users are confused by these parameters  and  do  not
know  how  to  set  them properly. This chapter will first review
these parameters and then discuss how to choose values for  them.
Special  emphasis  is given to avoiding interoperability problems
that may appear when communicating with  non-net.exe  implementa-
tions of AX.25.

9.1.  Hardware Parameters


9.1.1.  Bufsize

This parameter is required by most  of  net.exe's  built-in  HDLC
drivers  (eg. those for the DRSI PCPA and the Paccomm PC-100). It
specifies the size  of  the  buffer  to  be  allocated  for  each
receiver  port.  HDLC  frames  larger  than  this value cannot be
received.

There is no default bufsize; it must be specified in  the  attach
command for the interface.

9.2.  AX25 Parameters

9.2.1.  Paclen

Paclen limits the size of the data field  in  an  AX.25  I-frame.
This  value  does  not include the AX.25 protocol header (source,
destination and digipeater addresses).

Since unconnected-mode (datagram)  AX.25  uses  UI  frames,  this
parameter has no effect in unconnected mode.

The default value of paclen is 256 bytes.



                        June 7, 1991





                           - 50 -


9.2.2.  Maxframe

This parameter controls the number of I-frames that  net.exe  may
send  on  an AX.25 connection before it must stop and wait for an
acknowledgement.  Since the AX.25/LAPB sequence number field is 3
bits wide, this number cannot be larger than 7.

Since unconnected-mode (datagram) AX.25 uses UI  frames  that  do
not  have  sequence  numbers,  this  parameter  does not apply to
unconnected mode.

The default value of maxframe in net.exe is 1.

9.3.  IP and TCP Parameters

9.3.1.  MTU

The MTU (Maximum Transmission Unit)  is  an  interface  parameter
that  limits the size of the largest IP datagram that it may han-
dle.  IP datagrams routed to an interface that  are  larger  than
its MTU are each split into two or more fragments.  Each fragment
has its own IP header and is handled by the network as if it were
a distinct IP datagram, but when it arrives at the destination it
is held by the IP layer until all of the other fragments  belong-
ing to the original datagram have arrived. Then they are reassem-
bled back into the complete, original IP  datagram.  The  minimum
acceptable  interface MTU is 28 bytes: 20 bytes for the IP (frag-
ment) header, plus 8 bytes of data.

There is no default MTU in net.exe; it must be explicitly  speci-
fied for each interface as part of the attach command.

9.3.2.  MSS

MSS (Maximum Segment Size) is a TCP-level parameter  that  limits
the  amount of data that the remote TCP will send in a single TCP
packet. MSS values are exchanged in the SYN (connection  request)
packets that open a TCP connection. In the net.exe implementation
of TCP, the MSS actually used by TCP is further reduced in  order
to  avoid  fragmentation  at the local IP interface. That is, the
local TCP asks IP for the MTU of the interface that will be  used
to reach the destination. It then subtracts 40 from the MTU value
to allow for the overhead of the  TCP  and  IP  headers.  If  the
result  is  less than the MSS received from the remote TCP, it is
used instead.

The default value of MSS is 512 bytes.

9.3.3.  Window

This is a TCP-level parameter that controls  how  much  data  the
local  TCP  will allow the remote TCP to send before it must stop
and wait for an acknowledgement. The actual window value used  by
TCP  when  deciding  how much more data to send is referred to as



                        June 7, 1991





                           - 51 -


the effective window.  This is the smaller  of  two  values:  the
window advertised by the remote TCP minus the unacknowledged data
in flight, and the congestion window, an  automatically  computed
time-varying estimate of how much data the network can handle.

The default value of Window is 2048 bytes.

9.4.  Discussion


9.4.1.  IP Fragmentation vs AX.25 Segmentation

IP-level fragmentation often makes it  possible  to  interconnect
two  dissimilar  networks, but it is best avoided whenever possi-
ble.  One reason is that when a single IP fragment is  lost,  all
other  fragments  belonging  to the same datagram are effectively
also lost and the entire datagram must be  retransmitted  by  the
source.   Even  without loss, fragments require the allocation of
temporary buffer memory at the destination, and it is never  easy
to decide how long to wait for missing fragments before giving up
and discarding those that have  already  arrived.   A  reassembly
timer  controls  this  process.  In net.exe it is (re)initialized
with the ip rtimer parameter (default 30 seconds)  whenever  pro-
gress is made in reassembling a datagram (i.e., a new fragment is
received).  It is not necessary that all of the fragments belong-
ing  to  a datagram arrive within a single timeout interval, only
that the interval between fragments be less than the timeout.

Most subnetworks that carry IP have MTUs of 576 bytes or more, so
interconnecting  them  with subnetworks having smaller values can
result in considerable fragmentation. For this reason, IP  imple-
mentors  working  with  links  or  subnets having unusually small
packet size limits are encouraged to use  transparent  fragmenta-
tion,  that  is, to devise schemes to break up large IP datagrams
into a sequence of link or subnet  frames  that  are  immediately
reassembled  on the other end of the link or subnet into the ori-
ginal, whole IP datagram without the use of  IP-level  fragmenta-
tion.  Such  a  scheme  is provided in AX.25 Version 2.1.  It can
break a large IP or NET/ROM datagram into  a  series  of  paclen-
sized  AX.25 segments (not to be confused with TCP segments), one
per AX.25 I-frame, for transmission and reassemble  them  into  a
single datagram at the other end of the link before handing it up
to the IP or NET/ROM  module.   Unfortunately,  the  segmentation
procedure  is a new feature in AX.25 and is not yet widely imple-
mented; in fact, net.exe is so far the only known implementation.
This  creates  some interoperability problems between net.exe and
non-net.exe nodes, in particular, standard  NET/ROM  nodes  being
used  to carry IP datagrams. This problem is discussed further in
the section on setting the MTU.

9.4.2.  Setting paclen and bufsize

The more data you put into an AX.25  I  frame,  the  smaller  the
AX.25  headers  are in relation to the total frame size. In other



                        June 7, 1991





                           - 52 -


words, by increasing paclen, you lower the AX.25  protocol  over-
head. Also, large data packets reduce the overhead of keying up a
transmitter, and this can be  an  important  factor  with  higher
speed modems. On the other hand, large frames make bigger targets
for noise and interference. Each link has  an  optimum  value  of
paclen that is best discovered by experiment.

Another thing to remember when setting paclen is that  the  AX.25
version  2.0  specification  limits  it  to  256  bytes. Although
net.exe can handle much larger values, some other AX.25 implemen-
tations (including digipeaters) cannot and this may cause intero-
perability problems. Even net.exe may have trouble  with  certain
KISS  TNCs  because  of fixed-size buffers. The original KISS TNC
code for the TNC-2 by K3MC can handle frames limited in size only
by the RAM in the TNC, but some other KISS TNCs cannot.

Net.exe's built-in HDLC drivers (SCC, PC-100, DRSI, etc) allocate
receive  buffers according to the maximum expected frame size, so
it is important that these devices be configured with the correct
bufsize. To do this, you must know the size of the largest possi-
ble frame that can be received.  The  paclen  parameter  controls
only  the  size of the data field in an I-frame and not the total
size of the frame as it appears on the air. The AX.25 spec allows
up  to  8 digipeaters, so the largest possible frame is (paclen +
72) bytes. So you should make bufsize at least this large.

Another important consideration is that the more recent  versions
of  NOS  improve interrupt response by maintaining a special pool
of buffers for use by the receive routines.   These  buffers  are
configured  by  the  memory  nibufs and memory ibufsize commands.
ibufsize defaults to 2048 bytes. The setting of  ibufsize  limits
bufsize;  in fact, attempting to set a larger value may cause the
driver not to work at all. This situation can be detected by run-
ning  the  memory status command and looking for a non-zero count
of Ibuffail events, although these events can  also  occur  occa-
sionally during normal operation.

One of the drawbacks of AX.25 that there is no way for  one  sta-
tion  to tell another how large a packet it is willing to accept.
This requires the stations sharing a channel to agree  beforehand
on a maximum packet size.  TCP is different, as we shall see.

9.4.3.  Setting Maxframe

For best performance on a  half-duplex  radio  channel,  maxframe
should always be set to 1. The reasons are explained in the paper
Link Level Protocols Revisited by  Brian  Lloyd  and  Phil  Karn,
which  appeared  in the proceedings of the ARRL 5th Computer Net-
working Conference in 1986.

9.4.4.  Setting MTU

TCP/IP header overhead considerations similar  to  those  of  the
AX.25  layer  when  setting  paclen  apply  when choosing an MTU.



                        June 7, 1991





                           - 53 -


However, certain  subnetwork  types  supported  by  net.exe  have
well-established MTUs, and these should always be used unless you
know what you're doing: 1500 bytes for Ethernet,  and  508  bytes
for  ARCNET.   The  MTU  for PPP is automatically negotiated, and
defaults to 1500.  Other subnet types, including SLIP and  AX.25,
are not as well standardized.

SLIP has no official MTU, but the most common implementation (for
BSD  UNIX)  uses  an  MTU of 1006 bytes.  Although net.exe has no
hard wired limit on the size of a received SLIP  frame,  this  is
not true for other systems.  Interoperability problems may there-
fore result if larger MTUs are used in net.exe.

Choosing an MTU for an AX.25 interface is more complex. When  the
interface operates in datagram (UI-frame) mode, the paclen param-
eter does not apply. The MTU effectively becomes  the  paclen  of
the  link.   However, as mentioned earlier, large packets sent on
AX.25 connections are automatically segmented  into  I-frames  no
larger  than paclen bytes.  Unfortunately, as also mentioned ear-
lier, net.exe is so far the only known implementation of the  new
AX.25  segmentation procedure. This is fine as long as all of the
NET/ROM nodes along a path are running  net.exe,  but  since  the
main  reason net.exe supports NET/ROM is to allow use of existing
NET/ROM networks, this is unlikely.

So it is usually important to avoid AX.25 segmentation when  run-
ning  IP  over  NET/ROM.  The way to do this is to make sure that
packets larger than paclen are never handed to AX.25.  A  NET/ROM
transport  header  is  5  bytes long and a NET/ROM network header
takes 15 bytes, so 20 bytes must be added to the size  of  an  IP
datagram  when figuring the size of the AX.25 I-frame data field.
If paclen is 256, this leaves 236 bytes for the IP datagram. This
is  the default MTU of the netrom pseudo-interface, so as long as
paclen is at least 256 bytes, AX.25  segmentation  can't  happen.
But  if  smaller  values  of paclen are used, the netrom MTU must
also be reduced with the ifconfig command.

On the other hand, if you're running IP directly on top of AX.25,
chances  are  all  of  the  nodes are running net.exe and support
AX.25 segmentation.  In this case there is no reason not to use a
larger MTU and let AX.25 segmentation do its thing. If you choose
an MTU on the order of 1000-1500 bytes,  you  can  largely  avoid
IP-level fragmentation and reduce TCP/IP-level header overhead on
file transfers to a very low level.  And you are  still  free  to
pick whatever paclen value is appropriate for the link.

9.4.5.  Setting MSS

The setting of this TCP-level parameter is somewhat less critical
than  the IP and AX.25 level parameters already discussed, mainly
because it is automatically lowered according to the MTU  of  the
local  interface  when a connection is created. Although this is,
strictly speaking, a protocol layering violation (TCP is not sup-
posed to have any knowledge of the workings of lower layers) this



                        June 7, 1991





                           - 54 -


technique does work well in practice.  However, it can be fooled;
for  example, if a routing change occurs after the connection has
been opened and the new local interface has a  smaller  MTU  than
the previous one, IP fragmentation may occur in the local system.

The only drawback to setting a large MSS is that it  might  cause
avoidable  fragmentation  at  some other point within the network
path if it includes a "bottleneck" subnet  with  an  MTU  smaller
than  that  of  the  local  interface.   (Unfortunately, there is
presently no way to know when this is the case.  There is ongoing
work  within  the  Internet  Engineering  Task  Force  on  a "MTU
Discovery" procedure to determine the largest datagram  that  may
be  sent  over  a given path without fragmentation, but it is not
yet complete.) Also, since the MSS you specify  is  sent  to  the
remote  system,  and  not all other TCPs do the MSS-lowering pro-
cedure yet, this might cause the remote  system  to  generate  IP
fragments unnecessarily.

On the other hand, a too-small MSS can result in  a  considerable
performance  loss,  especially  when operating over fast LANs and
networks that can handle larger packets. So the  best  value  for
MSS is probably 40 less than the largest MTU on your system, with
the 40-byte margin allowing for the TCP and IP headers. For exam-
ple,  if  you  have  a SLIP interface with a 1006 byte MTU and an
Ethernet interface with a 1500 byte MTU, set MSS to  1460  bytes.
This allows you to receive maximum-sized Ethernet packets, assum-
ing the path to your system does not have any bottleneck  subnets
with smaller MTUs.

9.4.6.  Setting Window

A sliding window protocol like TCP cannot transfer more than  one
window's  worth  of  data  per  round trip time interval. So this
TCP-level parameter controls the ability of  the  remote  TCP  to
keep a long "pipe" full. That is, when operating over a path with
many hops, offering a large TCP window will help keep  all  those
hops busy when you're receiving data. On the other hand, offering
too large a window can congest the network if  it  cannot  buffer
all  that  data. Fortunately, new algorithms for dynamic control-
ling the effective TCP flow control window  have  been  developed
over  the  past  few  years and are now widely deployed.  Net.exe
includes them, and you can watch them  in  action  with  the  tcp
status  <tcb>  or  socket  <sockno>  commands.  Look at the cwind
(congestion window) value.

In most cases it is safe to set the TCP window to a small integer
multiple  of  the  MSS  (eg.  4 times), or larger if necessary to
fully utilize a high bandwidth*delay product path. One  thing  to
keep  in  mind, however, is that advertising a certain TCP window
value declares that the system has that much buffer space  avail-
able  for  incoming  data.  Net.exe does not actually preallocate
this space; it keeps it in a common pool and may well  "overbook"
it,  exploiting  the  fact that many TCP connections are idle for
long periods  and  gambling  that  most  applications  will  read



                        June 7, 1991





                           - 55 -


incoming  data  from  an active connection as soon as it arrives,
thereby quickly freeing the buffer memory.  However, it is possi-
ble  to  run  net.exe out of memory if excessive TCP window sizes
are advertised and either the applications go to  sleep  indefin-
itely (eg. suspended Telnet sessions) or a lot of out-of-sequence
data arrives.  It is wise to keep an eye on the amount of  avail-
able  memory  and  to  decrease the TCP window size (or limit the
number of simultaneous connections) if it gets too low.

Depending on the channel access method and link  level  protocol,
the  use  of  a  window setting that exceeds the MSS may cause an
increase in channel collisions. In particular, collisions between
data  packets  and  returning acknowledgements during a bulk file
transfer may become common. Although this is, strictly  speaking,
not TCP's fault, it is possible to work around the problem at the
TCP level by decreasing the window so that the protocol  operates
in  stop-and-wait  mode.  This is done by making the window value
equal to the MSS.

9.5.  Summary

In most cases, the default values provided by net.exe for each of
these  parameters will work correctly and give reasonable perfor-
mance. Only in special circumstances such  as  operation  over  a
very  poor  link or experimentation with high speed modems should
it be necessary to change them.

10.  Mail Forwarding

10.1.  Intended audience

This section is intended for the NOS system operator desiring  to
enable  the  forwarding  of  mail  to other systems. They are NOT
intended as a user guide for the mail capabilities of NOS.

10.2.  Background

This section of the NOS docs deals with the intricacies  of  mail
forwarding.  You  should  read  and understand this documentation
thoroughly before attempting to forward mail through your NOS box
to  the AX.25 BBS world, otherwise you might grossly misconfigure
your system and be the  unhappy  recipient  of  flames  from  BBS
sysops.

This section does NOT deal with the minutae of  the  mailbox  and
its  various  commands;  it  assumes that you understand concepts
such as user areas (both public and private) and how to list  and
send  mail. If you need help with these, please look elsewhere in
the NOS docs.

Apart from the usual domain.txt and  other  files  necessary  for
ordinary  functionality  of NOS, three files are important in the
mail forwarding process. These  are:  /spool/forward.bbs,  /alias
and  /spool/rewrite.  The contents of these will now be addressed



                        June 7, 1991





                           - 56 -


individually.

10.3.  /spool/forward.bbs

This file describes the actions taken by  NOS  in  forwarding  to
AX.25  BBSes.  The  file contains a series of forwarding records,
each record being separated by a  line  containing  two  or  more
hyphens. The template for a forwarding record is:

BBS callsign
Connection route
Connection commands                <zero or more lines>
List of areas to be forwarded      <one per line>
------------                       <end of record>

10.4.  BBS callsign

This is simply the ordinary call of the  remote  BBS.  A  typical
(but not random!) entry might be simply the line:

sm0rgv

The callsign may be followed,  on  the  same  line,  by  a  comma
separated  list  of  valid  intervals  when forwarding is to take
place. Each valid interval is a four digit number: the first  two
digits are the beginning hour of the valid interval, the last two
digits are the final hour of the valid interval. For example,  if
the first line of a forwarding record looks like:

sm0rgv 0006,1414

then forwarding to sm0rgv will take place only during hours  num-
bered  00, 01, 02, 03, 04, 05, 06 and 14. Ticks of the mbox timer
outside of these times will not cause mail  to  be  forwarded  to
sm0rgv. The default interval for forwarding is 0023.

10.5.  Connection route

This is the method by which communication is  to  be  established
with  the  remote BBS. The first token on the line is the type of
protocol to be used. This is one of ax25, netrom or tcp.  Follow-
ing  this  is  whatever  further  information the chosen protocol
requires to make the connection. An example connection route  for
a simple ax25 connection on interface ax0 is:

ax25 ax0 g3dlh


10.6.  Connection commands

Connection commands may, optionally, follow the connection route.
These take the form of a full stop (period), followed by the com-
mand which will be transmitted once the connection defined in the
first line of the connection route is established.



                        June 7, 1991





                           - 57 -


For example, suppose that we wish to establish a  netrom  connec-
tion with sm0rgv-2, through the netrom node #sth67. Then the con-
nection route and connection command portion of the record  would
look like:

netrom #sth67
 .c sm0rgv-2     [ Please note that the full stop would be placed at
                   the beginning of the line; I have placed it here
                   indented by one column simply so that gateways
                   which handle this message do not complain at
                   having a line beginning with a full stop; this
                   convention is followed throughout this documentation]

If the station is reached through  digipeating,  then  the  digi-
peater  callsigns  should be in the ax25 route to the destination
callsign.  That is, if you wish  to  forward  traffic  to  w0ljf,
using k2na as a digipeater, then you should have the line:

ax25 route add w0ljf k2na

in your autoexec file.


10.7.  List of areas to be forwarded

This is a list, one per  line,  of  entries  in  the  /spool/mail
directory  which will be forwarded to the remote BBS. An entry of
the form:

callsign

will cause the file /spool/mail/callsign.txt to  be  scanned  for
unread messages. Any such messages are sent to the remote BBS and
deleted from the file.

One can also forward user areas using this mechanism. To do this,
simply  place  a  line  containing  the  name  of the area in the
record. So, to forward amsat bulletins to the BBS, one would have
a line:

amsat

This will search the  /spool/mail/amsat.txt  file;  any  messages
contained  therein  which  have  not been forwarded to the BBS in
question will be forwarded. They will NOT be deleted. The  deter-
mining factor as to whether or not entries are deleted is that if
the filename is present in the /spool/areas file, then  there  is
NO deletion, otherwise there is.

Please note that ONLY FILES IN /spool/mail are checked.  In  par-
ticular, the outbound SMTP mail queue is NOT checked.






                        June 7, 1991





                           - 58 -


10.8.  Changing the recipient address

Normally, NOS uses the information in  the  To:  header  line  to
determine  the parameters used by the "S" command during BBS for-
warding. As the  To:  header  is  unchanged  by  all  /alias  and
/spool/rewrite  machinations,  the  mail  will be sent to the BBS
addressed precisely as the originator of the  message  typed  it.
Occasionally,  one  might  want to change this behaviour. In this
case, a line of the form:

area  new_address

in the list of areas to be forwarded will replace the  originally
typed destination with the string new_address instead.

11.  /alias

The alias file is used to map LOCAL names to other  names,  which
may  be either local or remote; additionally, from a single input
message, the alias file permits one to  produce  multiple  output
messages.  Thus, typical uses for the /alias file are: converting
one local name to another, converting a local name  to  a  remote
name,  and  exploding  a  mail message so that it is passed on to
several recipients.

The format of a record in the alias file is very simple:

aliasname       recipient1 recipient2 recipient3
<tab> or <SP>   recipient4 ... recipientN


There is no separation between records in the /alias  file  other
than a newline.

The aliasname is a local username; that is, it does  not  contain
an  "@" symbol. When the alias file is processed, if the destina-
tion of the message matches precisely  the  aliasname,  then  the
mail is redirected to ALL of the alieased recipients.

Scanning of the /alias file is performed by the SMTP server.  The
SMTP  timer  (which  controls the SMTP client) is kicked whenever
the mailbox or SMTP server queues something for delivery by SMTP.
Mail  transport  within  a single NOS system is performed through
the SMTP client/server mechanism. The result of  these  facts  is
that  as  soon  as a piece of mail is entered to the mailbox, the
SMTP client is kicked and attempts to deliver the mail (which has
already  been  scanned  by the rewrite mechanism - see below). If
the mail is local to the NOS system (i.e.  no  "@"  sign  in  the
address),  then the /alias file will be scanned and the name map-
pings take place.

A few lines in the /alias file might look something like:

bdale   bdale@n3eua



                        June 7, 1991





                           - 59 -


local   fred@k0yum bdale@n3eua [e-mail]
        n5op@n5op jim@k0jtz n0esg@n0esg
g4bki   g4bki@gb7bil._2712.gbr.eu


The system must know how to deliver traffic to each of the  indi-
vidual  addresses  in  the style in which they are entered in the
/alias file.  If the system does not know how to deliver  one  of
the  new addresses, then it will send it to the SMTP gateway sta-
tion defined by the 'smtp gateway' command.

Note that it is reasonable, and  sometimes  desireable,  to  have
alias records of the form:

area    area dest1 dest2 ...

As the /alias file is scanned only once (see  below),  this  does
not result in an infinite recursion.

12.  /spool/rewrite


The rewrite file is used to perform a one-to-one mapping  between
destination   addresses   as  received  by  NOS  and  destination
addresses as actually used by NOS. Each record within the rewrite
file  comprises  a  single  line,  containing either two or three
entries separated by spaces. The  first  field  is  the  template
field;  if  a  destination  address  matches  the template, it is
replaced by the second field. The third field, which is optional,
is  the single letter "r", which, if present, tells NOS to rescan
the rewrite file, using the new destination address to attempt to
match against the templates.

A template may contain asterisks. These stand for a match of  any
number  of  characters (including zero). In the second field, the
character "$", followed by a single digit in the range  1  to  9,
represents the string that matched the respective asterisk in the
template. By way of example, suppose that there is a line in  the
rewrite file which looks like:

*@* $1%$[e-mail]

Then, any traffic reaching the system through the mailbox or  the
SMTP server, but which is supposed to go to a remote system, will
be redirected to go through g1emm.ampr.org. Suppose that  a  user
logs on, and sends a message to n0gbe@nq0i. Then the rewrite file
attempts to match "n0gbe@nq0i" against the entry *@*. It matches,
and  assignes $1 the value n0gbe, and $2 the value nq0i. The mail
file as written to the disk will no longer be to n0gbe@nq0i, but,
rather,    to    [e-mail].   [The   nomenclature
station1%station2@station3  means  the   final   destination   is
station1@station2,  and  this traffic is to be routed through the
gateway station3.]




                        June 7, 1991





                           - 60 -


As soon as a template match is found, the conversion is performed
and  scanning  is stopped, unless the third "r" field is present,
in which case scanning restarts from the top of the file.

N.B. It is a good idea to have a line of the form:

*@*.ampr.org $1@$2.ampr.org

at the beginning of  your  rewrite  file.  This  will  cause  all
amprnet  traffic  to  be caught early in the rewrite scan, and no
further scanning (and, hence, no unexpected  substitutions)  will
take place.

12.1.  Scanning procedure

The two files which are used  to  determine  the  disposition  of
traffic  are scanned under slightly different circumstances. Note
that neither the /alias nor the  /spool/rewrite  scan  makes  any
actual changes to the contents of the traffic. In particular, the
To: field remains exactly as it was first entered into  the  sys-
tem.

There are four possible entry routes for traffic into the system:
SMTP,  through  the  mailbox  by a user, through the mailbox by a
BBS, and via an external program (like BM)  or  creation  of  the
files manually.  NOS determines if a piece of traffic was entered
into the system by a BBS by looking for a BBS system ID (like the
"[NET-H$]"  block issued by NOS) on the incoming connection prior
to messages being uploaded.

12.2.  Traffic received by SMTP server

1. The rewrite file is scanned and any  changes  applied  (unless
the traffic was recieved through the local mailbox; in that case,
this step does not occur);
2. If the traffic appears to be local  then  the  alias  file  is
scanned and any changes or explosions applied.
3. Any copies local to  the  system  are  delivered;  copies  for
remote delivery are placed in the SMTP queue.

12.3.  Traffic received by mailbox from user

1. The rewrite file is scanned and any changes applied;
2. The traffic is passed to the SMTP client.

12.4.  Traffic received by mailbox from BBS

1. The rewrite file is scanned and any changes applied;
2. The traffic is passed to the SMTP client.

12.5.  Traffic entered by external mechanism

1. No scanning occurs;
2. The traffic is passed to the SMTP client.



                        June 7, 1991





                           - 61 -


12.6.  Headers

Appropriate RFC-822 headers are added to  all  incoming  traffic.
Traffic  entering  through the mailbox recieves a full complement
of RFC-822 headers; traffic coming through the  SMTP  server  has
only  a "Received:" header applied. On forwarding to a BBS, if an
item of traffic contains BBS R: headers, the  RFC-822  header  is
converted to an appropriate R: line at the time that NOS forwards
the message. (This change only occurs for  BBS  forwarding;  for-
warding by SMTP retains the RFC-822 headers.)

12.7.  Bulletin Identifiers (BIDs)

The AX.25 BBS system has evolved a reasonably  efficient  way  of
reducing  overhead  when forwarding bulletins. When a bulletin is
originated on a BBS, it is given  a  unique  bulletin  identifier
(BID).  This BID should (theoretically) travel with the bulletin,
and should never be changed during the distribution of  the  bul-
letin.  Each  system  keeps track of all received BIDs. If a for-
warding station wishes to forward a bulletin to a BBS,  then  the
receiving station checks its local list of known BIDs and informs
the transmitting station if it already posesses the  bulletin  in
question.  The  NOS  mailbox  conforms to this protocol. Received
BIDs are stored in the file /spool/history, and  are  encoded  in
the Message-ID: header line of the message by NOS.  Messages for-
warded from areas listed in the /areas file will have  their  BID
(re)generated  from  the Message-ID: line. Note that ALL messages
from public areas are forwarded with a BID, whether  or  not  the
message was produced with the "SB" command. Like other BBSes, NOS
will inform a transmitting station not to transmit a bulletin  if
it  is one that NOS already has locally; likewise, it understands
similar messages from other stations to which it  tries  to  for-
ward.

Note that the BID mechanism is not a part of the SMTP  world.  If
you  are forwarding bulletins through SMTP, there is no mechanism
by which the receiving station can reject the attempted  delivery
of a bulletin, even if it already exists on the recipient system.
(Note that a possible  workaround  is  to  deliver  bulletins  to
TCP/IP  stations  using  TCP  instead of SMTP. Alternatively, one
could use NNTP, as NNTP commands utilise  the  Message-ID:  line,
from  which  the  BID is derived.) The BID is preserved no matter
which mechanism is used to deliver the bulletin.


12.8.  Traffic in practice

Now, the big question is, how does one set up these various files
to perform intelligent manipulation of mail? A number of examples
follow.  Note that, often, there is more than one way  to  accom-
plish  an  objective.  The following are merely examples (and not
necessarily the most efficient  method  possible  for  any  given
case). The format used will be:




                        June 7, 1991





                           - 62 -


typed destination -> intended destination

followed by the necessary entries in the alias (/alias),  rewrite
(/spool/rewrite) and forwarding (/spool/forward.bbs) files.


12.9.  Using familiar names - SMTP destination

bdale -> [e-mail]

alias:
bdale   [e-mail]

rewrite:
forward:


12.10.  Exploding local mail

sysops -> nq0i, [e-mail]

alias:
sysops  nq0i n5op@[e-mail]

rewrite:
forward:


12.11.  Using familiar names - BBS forwarding

g4bki -> g4bki@gb7bil._2712.gbr.eu, to be forwarded by ai0c

alias:
rewrite:
forward:
ai0c
ax25 ax1 ai0c
g4bki g4bki@gb7bil._2712.gbr.eu
ai0c


12.12.  Handling incoming bulletins by subject

tcpip@* -> nq0i, tcpip, [e-mail], ai0c@ai0c [a BBS]

alias:
tcpip   nq0i tcpip [e-mail] ai0c

rewrite:
tcpip@* tcpip

forward:
ai0c
ax25 ai0c



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                           - 63 -


ai0c

Let's walk through the above example. An incoming item  comes  in
addressed  to  TCPIP@ALLUS.  A  scan  is made through the rewrite
file, and a match is found. The item is redirected to tcpip.  The
alias  file  is scanned; a total of four copies of the item exist
after this, three in local areas tcpip, nq0i and ai0c, and one on
the SMTP queue (for [e-mail]). When the mailbox timer
next ticks, the mail in the local ai0c area will be forwarded  on
the ax1 interface to ai0c.


12.13.  Routing based on Hierarchical addressing


Wyoming -> KE7VS (SMTP)
Nebraska -> AG0N (BBS over the NETROM, NETROM ID WNBBS)
Europe -> W0LJF (BBS over AX.25)

alias:
rewrite:
*.noam            $1.na r
*.us              $1.usa.na r
*.usa             $1.usa.na r

*.ne              $1.ne.usa.na r
*.wy              $1.wy.usa.na r

*@*.*.wy.usa.na   $1%$2.$3.wy.usa.na@ke7vs
*@*.wy.usa.na     $1%$2.wy.usa.na@ke7vs

*.ne.usa.na     ag0n

*.eu            w0ljf

forward:
ag0n
netrom ax0 wnbbs
ag0n
----------
w0ljf
ax25 ax1 w0ljf
w0ljf
----------

Why is the example rewrite file apparently so  complicated?  This
is  to handle poorly constructed hierarchical addresses in a rea-
sonable way.  A full U.S.  hierarchical  address  has  the  form:
callsign@BBS.#localid.state.usa.na.  Many states have no #localid
field. In the example rewrite file above, the first  three  lines
convert  non-standard,  but  frequently used, U.S. designators to
the more standard format. It is common for users  not  to  use  a
full hierarchical address if the destination is relatively local.
For eample, a user might easily use only .wy instead of the  full



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                           - 64 -


grouping  of two lines handles this problem. Note the third, "r",
field in all the entries so far.

The remainder of the file handles properly formatted hierarchical
addresses.  The  two  Wyoming  entries  handle the cases with and
without a #localid field. Differentiation between these cases  is
not necessary for BBS forwarding.

12.14.  General bulletin handling

The details of bulletin handling will vary somewhat from place to
place,  as there are several distinct styles of bulletin handling
currently in use in the AX.25 BBS world. In general, it is neces-
sary  to  arrange  one's system so that it accepts bulletins from
BBSes, forwards them to one or more stations,  and  also  handles
intelligently bulletins input by users into NOS.

Suppose that we sish to handle bulletins @JUNK. We are to deposit
them  locally in the junk area, and also forward to BBS g4bki. We
also know that we generally receive @JUNK bulletins from g4amj, a
local BBS which handles much bulletin traffic.
alias:
rewrite:
*@junk   junk

forward:
g4bki
ax25 ax1 g4bki
g4bki
junk
----------
g4amj
ax25 ax1 g4amj
g4amj
junk
----------

All incoming @JUNK traffic is written to  the  junk  area  (which
should  be an explicit entry in the /spool/areas file). Each tick
of the mailbox timer, NOS scans the junk  area  for  traffic  not
forwarded  to  g4bki or g4amj and attempts to deliver unforwarded
bulletins. Usually, g4amj will respond with a "Have  it"  message
and the bulletin will not be forwarded. Any bulletins @JUNK depo-
sited locally by users will automatically be sent to  both  g4bki
and g4amj.

13.  Questions and Answers

Q. Under what circumstances does NOS request  reverse  forwarding
from a BBS?

A. NOS requests a reverse forward after completing  any  forwards
of  its own to the BBS. If no traffic was queued for a given BBS,
then no connection is attempted, so no reverse forward request is



                        June 7, 1991





                           - 65 -


issued.

Q. What kinds of message types does the NOS mbox support?

A. Basically, NOS supports all two letter commands starting  with
an  "S".  If  the  mailbox  has  not  received an SID banner (the
"[NET-H$]") from a connected station, then  an  SF  command  will
send a followup to the address specified on the command line. The
SR command will send a reply to the current message. One can also
issue  the command "SR <number>", where <number> is the number of
the message to which you want to  generate  a  reply.  All  other
variations  cause  an  X-BBS-Msg-Type:  header to be added to the
message. When a message with such a line is forwarded to  a  BBS,
it  is  sent  to the BBS with the appropriate message type as the
second letter in the "S" command to the BBS.

If NOS has received a valid SID, then ALL S commands are  handled
by the X-BBS-Msg-Type: mechanism outlined above.







































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                           - 66 -


14.  Logic map of the mailbox


============== AX.25 === NET/ROM === Ethernet === Loopback =================
       |                   |                   |                   |
       |                   |                   |                   |
+--------------+    +--------------+    +--------------+    +--------------+
|              |    |              |    |              |    |              |
|   Mailbox    |    | SMTP client  |    | SMTP server  |    | BBS Forward  |
|              |    |              |    |              |    |              |
+--------------+    +--------------+    +--------------+    +--------------+
       |                   ^                   |                   ^
       |                   |                   |                   |
       v                   |                   v                   |
+--------------+    +--------------+    +--------------+    +--------------+
|              |    |              |    |              |    |              |
| Add RFC822   |    | Use MX or A  |    | Add Received |    | Add own R:   |
| header suite |    | type records |    | line         |  +>| line         |
|              |    |              |    |              |  | |              |
+--------------+    +--------------+    +--------------+  | +--------------+
       |                   ^                   |          |        ^
       |                   |                   |          |        |
       v                   |                   v          |        |
+--------------+    +--------------+    +--------------+  | +--------------+
|              |    |              |    |              |  | |              |
| Get Rewrite  |    | Use optional |    | Apply Rewrite|  | | Strip RFC822 |
| file address |    | SMTP gateway |    | file address |  | | header suite |
|              |    |              |    |              |  | |              |
+--------------+    +--------------+    +--------------+  | +--------------+
       |                   ^                   |          |        ^
       |                   |                   |          |        | Yes
       v                   |                   v          |        |
+--------------+           |            +--------------+  | +--------------+
|              |   No      |            |              |  | |              |
| Local addr?  |-------+   |            | Alias file   |  +-| Any R: lines?|
|              |       |   |            |              | No |              |
+--------------+       |   |            +--------------+    +--------------+
       |               |   |                |  |  |                ^
       | Yes           |   |                |  |  |                |
       v               |   |                v  v  v                |
+--------------+       v   |            +--------------+    +--------------+
|              |    +--------------+    |              |    |              |
| Apply Rewrite|    |              | No | Local        |Yes | /spool/mail/ |
| file address |--->| SMTP queue   |<---| address?     |--->| directory    |
|              |    |              |    |              |    |              |
+--------------+    +--------------+    +--------------+    +--------------+

15.  Credits

Several people have contributed to this manual. I would  particu-
larly  like  to thank Bill Simpson and Michael Westerhof, KA9WSB,
for their significant editorial contributions to  this  document.
Deborah  Swanberg  wrote  the original BOOTP documentation,.  and
G4AMJ/NQ0I and SM0RGV contributed the section on mail forwarding.



                        June 7, 1991





                           - 67 -


Although I am the primary author of this software  package,  many
others  have  contributed  substantial additions and refinements.
Here is a partial list; additions and  corrections  are  welcome.
See  the  individual  source code files for additional authorship
details.

15.1.  ARCNET

Written by Russ Nelson of Clarkson University.

15.2.  Autodialer

Bill  Simpson  substantially  rewrote  my  original  version  and
created a much improved control file format.

15.3.  Bootstrap Protocol (BOOTP)

Written by Deborah Swanberg of the University of Michigan.

15.4.  Domain resolver

Bill Simpson substantially extended my original  version,  adding
record caching and automatic expiration.

15.5.  DRSI driver

Written by Stu Phillips, N6TTO.

15.6.  Eagle 8530 board driver

Written by Art Goldman, WA3CVG, and Richard Bisbey, NG6Q.

15.7.  HAPN 8273 HDLC board driver

Written by Jon Bloom, KE3Z, with fixes by John Tanner, VK2ZXQ.

15.8.  Hop Check utility

Written by Katie Stevens of UC Davis; enhancements by Bill  Simp-
son.

15.9.  Mailbox server & SMTP

My original,  primitive  SMTP  server  was  vastly  enhanced  and
expanded  by  Bdale  Garbee,  N3EUA and Dave Trulli, NN2Z. Anders
Klemets, SM0RGV,  wrote  the  first  "mailbox"  specifically  for
AX.25;  he then expanded it into a full-blown bulletin board sys-
tem and integrated it with the SMTP facilities.

15.10.  NET/ROM

The original NET/ROM code was done by Dan  Frank,  W9NK.  It  was
ported to the NOS platform by Anders Klemets, SM0RGV.




                        June 7, 1991





                           - 68 -


15.11.  Netnews Transfer Protocol (NNTP)

Written by Anders Klements, SM0RGV, with help from  Bernie  Roehl
and Gerard Van Der Grinten, PA0GRI.

15.12.  Packet Drivers

Although not really part of this  package,  the  Clarkson  Packet
Driver Collection by Russ Nelson of Clarkson University has enor-
mously enhanced the utility of this package by allowing it to use
virtually every PC Ethernet controller board on the market.

15.13.  PI 8530 DMA HDLC driver

Written by Dave Perry, VE3IFB.

15.14.  Post Office Protocol (POP)

Originally authored by Mike Stockett, WA7DYX. Updates and modifi-
cations  by  Allen  Gwinn, N5CKP, Gerard Van Der Grinten, PA0GRI,
and Mark Edwards, WA6SMN.

15.15.  Point to Point Protocol (PPP)

Written by Katie Stevens of  UC  Davis,  based  on  the  original
implementation  by  Drew  Perkins of CMU. Updated by Bill Simpson
and Glenn McGregor of the University of Michigan.

15.16.  Routing Information Protocol (RIP)

Original (pre-NOS) version written by Al Broscious N3FCT.

15.17.  SCC - Generic 8530 driver

Originally written for the old "NET" code by Rob Janssen, PE1CHL.
Ported to NOS by Ken Mitchum, KY3B.

15.18.  Socket-level stream compression

Written by Anders Klemets, SM0RGV

15.19.  TCP/IP Header Compression

Adapted from Van Jacobson's original BSD UNIX  implementation  by
Katie Stevens of UC Davis. Updated by Bill Simpson.












                        June 7, 1991