 
 
 
 
 
 
 
 
 
             NET User Reference Manual (NOS Version)
 
 
                         Phil Karn, KA9Q
 
 
 
 
 
 
_1.  _T_h_e _N_E_T._E_X_E _P_r_o_g_r_a_m
 
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.  _I_n_s_t_a_l_l_a_t_i_o_n
 
Net.exe uses the following directory structure:
 
        /net
        /net/spool
        /net/spool/help
        /net/spool/mail
        /net/spool/mqueue
        /net/spool/rqueue
        /net/spool/news
 
 
The "/net" directory is not strictly necessary, and  defaults  to
the  root of the current drive.  Any name may be chosen using the
-d   command-line   option   (described   below).    The   alias,
autoexec.net, dialer, domain.txt and ftpusers configuration files
are located here.
 
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.
 
The alias, forward.bbs and rewrite files  are  described  in  the
document "maildoc", which should be found at the same location as
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 2 -
 
 
this file.
 
_1._2.  _n_e_t [-_b] [-_s <_s_o_c_k_e_t_s>] [-_d <_d_i_r_e_c_t_o_r_y>] [<_s_t_a_r_t_u_p _f_i_l_e>]
 
_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 _s_o_c_k_e_t 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.  _S_t_a_r_t_u_p _f_i_l_e
 
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.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 3 -
 
 
_2.  _C_o_n_s_o_l_e _m_o_d_e_s
 
The console may be in one of two modes: _c_o_m_m_a_n_d _m_o_d_e and _c_o_n_v_e_r_s_e
_m_o_d_e.   In  _c_o_m_m_a_n_d _m_o_d_e, the prompt net> is displayed and any of
the commands described in the Commands chapter  may  be  entered.
In  _c_o_n_v_e_r_s_e  _m_o_d_e,  keyboard input is processed according to the
_c_u_r_r_e_n_t _s_e_s_s_i_o_n.
 
Sessions come in many types, including _T_e_l_n_e_t, _F_T_P, _A_X_2_5, _N_E_T_R_O_M,
_P_i_n_g,  _M_o_r_e, _H_o_p_c_h_e_c_k and _T_i_p.  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.
 
The keyboard also has _c_o_o_k_e_d and _r_a_w states.   In  _c_o_o_k_e_d  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
and  erase  the  last  character,  respectively.   Hitting either
return or line feed passes the complete line up to  the  applica-
tion.   In _r_a_w state, each character is immediately passed to the
application as it is typed.
 
The keyboard is always in _c_o_o_k_e_d state in command  mode.   It  is
also  _c_o_o_k_e_d 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 _c_o_m_m_a_n_d _m_o_d_e  by  hit-
ting  the  F10  key.   On  other systems, the user must enter the
_e_s_c_a_p_e character, which is by default control-]  (hex  1d,  ASCII
GS).  (Note that this is distinct from the ASCII character of the
same name).  The _e_s_c_a_p_e 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.
 
 
 
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 4 -
 
 
_3.  _C_o_m_m_a_n_d_s
 
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
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.)
 
_3._1.  <_C_R>
 
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.
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 5 -
 
 
_3._3.  #
 
Commands starting with the hash mark (#)  are  ignored.  This  is
mainly useful for comments in the autoexec.net file.
 
_3._4.  _a_b_o_r_t [<_s_e_s_s_i_o_n #>]
 
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.  _a_r_p
 
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.
If the link address  is  currently  unknown,  the  number  of  IP
datagrams awaiting resolution is also shown.
 
_3._5._1.  _a_r_p _a_d_d <_h_o_s_t_i_d> _e_t_h_e_r_n_e_t |  _a_x_2_5  <_e_t_h_e_r_n_e_t  _a_d_d_r_e_s_s>  |
<_a_x_2_5__a_d_d_r_e_s_s>
 
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.  _a_r_p _p_u_b_l_i_s_h <_h_o_s_t_i_d> _e_t_h_e_r_n_e_t | _a_x_2_5 <_e_t_h_e_r_n_e_t _a_d_d_r_e_s_s> |
<_a_x_2_5__a_d_d_r_e_s_s>
 
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.  _a_r_p _d_r_o_p <_h_o_s_t_i_d> _a_x_2_5 | _e_t_h_e_r_n_e_t
 
Remove the specified entry from the ARP table.
 
_3._5._4.  _a_r_p _f_l_u_s_h
 
Drop all automatically-created entries in  the  ARP  table;  per-
manent entries are not affected.
 
_3._6.  _a_s_y_s_t_a_t
 
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
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 6 -
 
 
configuration  flags; these indicate whether the port is a 16550A
chip, the _t_r_i_g_g_e_r _c_h_a_r_a_c_t_e_r 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 _t_r_i_g_g_e_r _c_h_a_r_a_c_-
_t_e_r 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  _h_i_g_h
_w_a_t_e_r _m_a_r_k.  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.
 
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.  _a_t_t_a_c_h <_h_w _t_y_p_e> ...
 
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
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 7 -
 
 
(eg. attach packet).  This produces a usage  message  giving  the
complete command format.
 
_3._8.  _a_x_2_5 ...
 
These commands are used for AX25 interfaces.
 
_3._8._1.  _a_x_2_5 _b_l_i_m_i_t [<_c_o_u_n_t>]
 
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 _b_i_n_a_r_y _e_x_p_o_n_e_n_t_i_a_l _b_a_c_k_-
_o_f_f.   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.  _a_x_2_5 _d_i_g_i_p_e_a_t [_o_n | _o_f_f]
 
Display or set the digipeater enable flag.
 
_3._8._3.  _a_x_2_5 _f_l_u_s_h
 
Clear the AX.25 "heard" list (see ax25 heard).
 
_3._8._4.  _a_x_2_5 _h_e_a_r_d
 
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  local  station  always
appears  first in the listing; the packet count actually reflects
the number of packets transmitted. This entry is  always  present
even if no packets have been sent.
 
_3._8._5.  _a_x_2_5 _i_r_t_t [<_m_i_l_l_i_s_e_c_o_n_d_s>]
 
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._6.  _a_x_2_5 _k_i_c_k <_a_x_c_b>
 
Force a retransmission on the specified AX.25 control block.
 
_3._8._7.  _a_x_2_5 _m_a_x_f_r_a_m_e [<_c_o_u_n_t>]
 
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.
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 8 -
 
 
_3._8._8.  _a_x_2_5 _m_y_c_a_l_l [<_c_a_l_l>]
 
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._9.  _a_x_2_5 _p_a_c_l_e_n [<_s_i_z_e>]
 
Limit the size of I-fields  on  new  AX.25  connections.   If  IP
datagrams  or  fragments  larger  than this are transmitted, they
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._1_0.  _a_x_2_5 _p_t_h_r_e_s_h [<_s_i_z_e>]
 
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._1_1.  _a_x_2_5 _r_e_s_e_t <_a_x_c_b>
 
Delete the  AX.25  connection  control  block  at  the  specified
address.
 
_3._8._1_2.  _a_x_2_5 _r_e_t_r_y [<_c_o_u_n_t>]
 
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.
 
_3._8._1_3.  _a_x_2_5 _r_o_u_t_e
 
Display the AX.25 routing table that specifies the digipeaters to
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 9 -
 
 
be used in reaching a given station.
 
_3._8._1_3._1.  _a_x_2_5 _r_o_u_t_e _a_d_d <_t_a_r_g_e_t> [_d_i_g_i_s ... ]
 
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
locally created entries, however.
 
_3._8._1_3._2.  _a_x_2_5 _r_o_u_t_e _d_r_o_p <_t_a_r_g_e_t>
 
Drop an entry from the AX.25 routing table.
 
_3._8._1_4.  _a_x_2_5 _s_t_a_t_u_s [<_a_x_c_b>]
 
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._1_5.  _a_x_2_5 _t_3 [<_m_i_l_l_i_s_e_c_o_n_d_s>]
 
Display or set the AX.25 idle "keep alive"  timer.  Value  is  in
milliseconds.
 
_3._8._1_6.  _a_x_2_5 _v_e_r_s_i_o_n [_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._1_7.  _a_x_2_5 _w_i_n_d_o_w [<_s_i_z_e>]
 
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.  _c_d [<_d_i_r_n_a_m_e>]
 
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._1_0.  _c_l_o_s_e [<_s_e_s_s_i_o_n>]
 
Close the specified  session;  without  an  argument,  close  the
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 10 -
 
 
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._1_1.  _c_o_n_n_e_c_t <_i_f_a_c_e> <_c_a_l_l_s_i_g_n> [<_d_i_g_i_p_e_a_t_e_r> ... ]
 
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.
 
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._1_2.  _d_e_l_e_t_e <_f_i_l_e_n_a_m_e>
 
Delete a filename in the current working directory.
 
_3._1_3.  _d_e_t_a_c_h <_i_f_a_c_e>
 
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._1_4.  _d_i_a_l_e_r <_i_f_a_c_e> <_s_e_c_o_n_d_s> <_h_o_s_t_i_d> <_p_i_n_g_s> <_d_i_a_l_e_r-_f_i_l_e>
 
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  <pings>
attempts,  the  autodialer will execute the special commands con-
tained in the <dialer-file>.
 
If the interval in <seconds> is zero, a previous  dialer  command
process  will  be removed.  If the number of <pings> is zero, the
<dialer-file> will be executed without pinging the <hostid>.
 
The file may have any valid name, and must be located in the con-
figuration  directory (see the Installion section).  The commands
in the file are described in the Dialer Subcommands chapter.
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 11 -
 
 
_3._1_5.  _d_i_r [<_d_i_r_n_a_m_e>]
 
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._1_6.  _d_i_s_c_o_n_n_e_c_t [<_s_e_s_s_i_o_n #>]
 
An alias for the close command (for the benefit of AX.25 users).
 
_3._1_7.  _d_o_m_a_i_n ...
 
These commands are used for access to the Domain Name Service.
 
_3._1_7._1.  _d_o_m_a_i_n _a_d_d_s_e_r_v_e_r <_h_o_s_t_i_d>
 
Add one or more  domain  name  server(s)  to  the  list  of  name
servers.
 
_3._1_7._2.  _d_o_m_a_i_n _d_r_o_p_s_e_r_v_e_r <_h_o_s_t_i_d>
 
Remove one or more domain name server(s) from the  list  of  name
servers.
 
_3._1_7._3.  _d_o_m_a_i_n _l_i_s_t_s_e_r_v_e_r_s
 
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._1_7._4.  _d_o_m_a_i_n _q_u_e_r_y <_h_o_s_t_i_d>
 
Send a query to a domain server asking for all  resource  records
associated with this <hostid>, and list the records.
 
_3._1_7._5.  _d_o_m_a_i_n _r_e_t_r_y [<_c_o_u_n_t>]
 
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._1_7._6.  _d_o_m_a_i_n _s_u_f_f_i_x [<_d_o_m_a_i_n _s_u_f_f_i_x>]
 
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).
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 12 -
 
 
_3._1_7._7.  _d_o_m_a_i_n _t_r_a_c_e [_o_n | _o_f_f]
 
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._1_7._8.  _d_o_m_a_i_n _c_a_c_h_e ...
 
These commands are used for the use of the resource  record  file
domain.txt, and the local memory cache.
 
_3._1_7._8._1.  _d_o_m_a_i_n _c_a_c_h_e _c_l_e_a_n [_o_n | _o_f_f]
 
Display or set the  flag  controlling  the  removal  of  resource
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._1_7._8._2.  _d_o_m_a_i_n _c_a_c_h_e _l_i_s_t
 
List the current contents of the local memory cache.
 
_3._1_7._8._3.  _d_o_m_a_i_n _c_a_c_h_e _s_i_z_e [<_c_o_u_n_t>]
 
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._1_7._8._4.  _d_o_m_a_i_n _c_a_c_h_e _w_a_i_t [<_s_e_c_o_n_d_s>]
 
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._1_8.  _e_c_h_o [_a_c_c_e_p_t | _r_e_f_u_s_e]
 
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
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 13 -
 
 
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  Nagle tinygram algorithm 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
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._1_9.  _e_o_l [_u_n_i_x | _s_t_a_n_d_a_r_d]
 
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._2_0.  _e_s_c_a_p_e [<_c_h_a_r>]
 
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._2_1.  _e_t_h_e_r_s_t_a_t
 
Display 3-Com Ethernet controller statistics (if configured).
 
_3._2_2.  _e_x_i_t
 
Exit the net.exe program and return to MS-DOS.
 
_3._2_3.  _f_i_n_g_e_r <_u_s_e_r@_h_o_s_t_i_d> [<_u_s_e_r@_h_o_s_t_i_d> ...]
 
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.
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 14 -
 
 
_3._2_4.  _f_t_p <_h_o_s_t_i_d>
 
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._2_5.  _h_e_l_p
 
Display a brief summary of top-level commands.
 
_3._2_6.  _h_o_p ...
 
These commands are used to test the connectivity of the network.
 
_3._2_6._1.  _h_o_p _c_h_e_c_k <_h_o_s_t_i_d>
 
Initiate a _h_o_p_c_h_e_c_k 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 _t_r_a_c_e_r_o_u_t_e
facility.
 
ICMP message tracing should be turned off before this command  is
executed (see the icmp trace command).
 
_3._2_6._2.  _h_o_p _m_a_x_t_t_l [<_h_o_p_s>]
 
Display or set the maximum TTL value to be used in hop check ses-
sions.  This effectively bounds the radius of the search.
 
_3._2_6._3.  _h_o_p _m_a_x_w_a_i_t [<_s_e_c_o_n_d_s>]
 
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._2_6._4.  _h_o_p _q_u_e_r_i_e_s [<_c_o_u_n_t>]
 
Display or set the number of UDP probes that will be sent at each
stage of the trace. The default is 3.
 
_3._2_6._5.  _h_o_p _t_r_a_c_e [_o_n | _o_f_f]
 
Display or set the flag that controls the display  of  additional
information during a hop check session.
 
_3._2_7.  _h_o_s_t_n_a_m_e [<_n_a_m_e>]
 
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.
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 15 -
 
 
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._2_8.  _h_s
 
Display statistics about the HS high speed HDLC driver  (if  con-
figured and active).
 
_3._2_9.  _i_c_m_p ...
 
These commands are used for the Internet Control Message Protocol
service.
 
_3._2_9._1.  _i_c_m_p _e_c_h_o [_o_n | _o_f_f]
 
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._2_9._2.  _i_c_m_p _s_t_a_t_u_s
 
Display statistics about the Internet  Control  Message  Protocol
(ICMP),  including  the number of ICMP messages of each type sent
or received.
 
_3._2_9._3.  _i_c_m_p _t_r_a_c_e [_o_n | _o_f_f]
 
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._3_0.  _i_f_c_o_n_f_i_g
 
Display a list of interfaces, with a short status for each.
 
_3._3_0._1.  _i_f_c_o_n_f_i_g <_i_f_a_c_e>
 
Display an extended status of the interface.
 
_3._3_0._2.  _i_f_c_o_n_f_i_g <_i_f_a_c_e> _b_r_o_a_d_c_a_s_t <_a_d_d_r_e_s_s>
 
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._3_0._3.  _i_f_c_o_n_f_i_g <_i_f_a_c_e> _e_n_c_a_p_s_u_l_a_t_i_o_n <_n_a_m_e>
 
Not fully implemented.
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 16 -
 
 
_3._3_0._4.  _i_f_c_o_n_f_i_g <_i_f_a_c_e> _f_o_r_w_a_r_d <_f_o_r_w_a_r_d-_i_f_a_c_e>
 
Set a forwarding interface for multiple channel  interfaces.   To
remove the forward, set <forward-iface> to <iface>.
 
_3._3_0._5.  _i_f_c_o_n_f_i_g <_i_f_a_c_e> _i_p_a_d_d_r_e_s_s <_h_o_s_t_i_d>
 
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.
 
_3._3_0._6.  _i_f_c_o_n_f_i_g <_i_f_a_c_e> _l_i_n_k_a_d_d_r_e_s_s <_h_a_r_d_w_a_r_e-_d_e_p_e_n_d_a_n_t>
 
Set the hardware dependant address for this interface.
 
_3._3_0._7.  _i_f_c_o_n_f_i_g <_i_f_a_c_e> _m_t_u <_m_t_u>
 
Set the MTU for this interface.  See the Setting ... MTU, MSS and
Window chapter for more information.
 
_3._3_0._8.  _i_f_c_o_n_f_i_g <_i_f_a_c_e> _n_e_t_m_a_s_k <_a_d_d_r_e_s_s>
 
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._3_0._9.  _i_f_c_o_n_f_i_g <_i_f_a_c_e> _r_x_b_u_f <?>
 
Not yet implemented.
 
_3._3_1.  _i_p ...
 
These commands are used for the Internet Protocol service.
 
_3._3_1._1.  _i_p _a_d_d_r_e_s_s [<_h_o_s_t_i_d>]
 
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._3_1._2.  _i_p _r_t_i_m_e_r [<_s_e_c_o_n_d_s>]
 
Display or set the IP  reassembly  timeout.  The  default  is  30
seconds.
 
_3._3_1._3.  _i_p _s_t_a_t_u_s
 
Display Internet Protocol (IP) statistics, such as  total  packet
counts and error counters of various types.
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 17 -
 
 
_3._3_1._4.  _i_p _t_t_l [<_h_o_p_s>]
 
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._3_2.  _i_s_a_t [_o_n | _o_f_f]
 
Display or set the AT flag.  Currently, there is no sure-fire way
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._3_2._1.  _k_i_c_k [<_s_e_s_s_i_o_n>]
 
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._3_3.  _l_o_g [_s_t_o_p | <_f_i_l_e_n_a_m_e>]
 
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._3_4.  _m_b_o_x
 
Display the status of the mailbox server system (if configured).
 
_3._3_5.  _m_e_m_o_r_y ...
 
These commands are used for memory allocation.
 
_3._3_5._1.  _m_e_m_o_r_y _f_r_e_e
 
Display the storage allocator free list. Each entry consists of a
starting address, in hex, and a size, in decimal bytes.
 
_3._3_5._2.  _m_e_m_o_r_y _s_i_z_e_s
 
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._3_5._3.  _m_e_m_o_r_y _s_t_a_t_u_s
 
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
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 18 -
 
 
heap  size,  and the amount of memory left over (i.e., not placed
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._3_6.  _m_k_d_i_r <_d_i_r_n_a_m_e>
 
Create a sub-directory in the current working directory.
 
_3._3_7.  _m_o_d_e <_i_f_a_c_e> [_v_c | _d_a_t_a_g_r_a_m]
 
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).
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 19 -
 
 
_3._3_8.  _m_o_r_e <_f_i_l_e> [<_f_i_l_e> ...]
 
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._3_9.  _p_a_r_a_m <_i_f_a_c_e> [<_p_a_r_a_m> ...]
 
Invoke a device-specific control routine.  On a KISS  TNC  inter-
face,  this  sends  control  packets  to the TNC.  Data bytes are
treated as decimal.  For example, param ax0 1 255  will  set  the
keyup timer (type field = 1) on the KISS TNC configured as ax0 to
2.55 seconds (255 x .01 sec).  On a  SLIP  interface,  the  param
command  allows  the  baud rate to be read (without arguments) or
set.  The implementation of this command for the  various  inter-
face drivers is incomplete and subject to change.
 
_3._4_0.  _p_i_n_g <_h_o_s_t_i_d> [<_l_e_n_g_t_h> [<_s_e_c_o_n_d_s> [<_i_n_c_f_l_a_g>]]]
 
Ping (send ICMP Echo Request packets to) the specified  host.  By
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._4_1.  _p_p_p ...
 
These commands are used for 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:
 
 
 
 
 
 
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 20 -
 
 
 
        attach asy 0x3f8 4 ppp pp0 4096 1500 9600
        dial pp0 30 <hostid> 3 dialer.pp0
        #
        ppp pp0 lcp local accm 0
        ppp pp0 lcp local compress address on
        ppp pp0 lcp local compress protocol on
        ppp pp0 lcp local magic on
        ppp pp0 lcp open active
        #
        ppp pp0 ipcp local compress tcp 16 1
        ppp pp0 ipcp open active
        #
        route add default pp0
 
 
_3._4_1._1.  _p_p_p <_i_f_a_c_e>
 
Display the status of the PPP interface.
 
_3._4_1._2.  _p_p_p <_i_f_a_c_e> _l_c_p ...
 
These commands are used for the LCP [Link Control Protocol]  con-
figuration.
 
_3._4_1._2._1.  _p_p_p <_i_f_a_c_e> _l_c_p _c_l_o_s_e
 
Shutdown the PPP interface.
 
_3._4_1._2._2.  _p_p_p <_i_f_a_c_e> _l_c_p _l_o_c_a_l ...
 
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._4_1._2._2._1.  _p_p_p <_i_f_a_c_e> _l_c_p _l_o_c_a_l _a_c_c_m [ <_b_i_t_m_a_p> | _a_l_l_o_w [_o_n  |
_o_f_f] ]
 
Display or set the Async Control Character Map.  The  default  is
0xffffffff.
 
_3._4_1._2._2._2.  _p_p_p <_i_f_a_c_e> _l_c_p _l_o_c_a_l _a_u_t_h_e_n_t_i_c_a_t_e [ _p_a_p  |  _n_o_n_e  |
_a_l_l_o_w [_o_n | _o_f_f] ]
 
Display or set the authentication protocol.  The default is none.
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 21 -
 
 
_3._4_1._2._2._3.  _p_p_p <_i_f_a_c_e> _l_c_p _l_o_c_a_l _c_o_m_p_r_e_s_s _a_d_d_r_e_s_s/_c_o_n_t_r_o_l [  _o_n
| _o_f_f | _a_l_l_o_w [_o_n | _o_f_f] ]
 
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._4_1._2._2._4.  _p_p_p <_i_f_a_c_e> _l_c_p _l_o_c_a_l _c_o_m_p_r_e_s_s _p_r_o_t_o_c_o_l [ _o_n | _o_f_f |
_a_l_l_o_w [_o_n | _o_f_f] ]
 
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._4_1._2._2._5.  _p_p_p <_i_f_a_c_e> _l_c_p _l_o_c_a_l _m_a_g_i_c [ _o_n | _o_f_f |  <_v_a_l_u_e>  |
_a_l_l_o_w [_o_n | _o_f_f] ]
 
Display or set the initial Magic  Number.   The  default  is  off
(zero).
 
_3._4_1._2._2._6.  _p_p_p <_i_f_a_c_e> _l_c_p _l_o_c_a_l _m_r_u [ <_s_i_z_e>  |  _a_l_l_o_w  [_o_n  |
_o_f_f] ]
 
Display or set the Maximum Receive Unit.  The default is 1500.
 
_3._4_1._2._2._7.  _p_p_p <_i_f_a_c_e> _l_c_p _l_o_c_a_l _d_e_f_a_u_l_t
 
Reset the options to their default values.
 
_3._4_1._2._3.  _p_p_p <_i_f_a_c_e> _l_c_p _o_p_e_n _a_c_t_i_v_e | _p_a_s_s_i_v_e
 
Wait for the physical layer to come up.  If active, initiate con-
figuration negotiation.  If passive, wait for configuration nego-
tiation from the remote.
 
_3._4_1._2._4.  _p_p_p <_i_f_a_c_e> _l_c_p _r_e_m_o_t_e ...
 
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._4_1._2._5.  _p_p_p <_i_f_a_c_e> _l_c_p _t_i_m_e_o_u_t [<_s_e_c_o_n_d_s>]
 
Display or set the interval to wait between configuration or ter-
mination attempts.  The default is 3 seconds.
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 22 -
 
 
_3._4_1._2._6.  _p_p_p <_i_f_a_c_e> _l_c_p _t_r_y ...
 
These commands are used for the various counters.
 
_3._4_1._2._6._1.  _p_p_p <_i_f_a_c_e> _l_c_p _t_r_y _c_o_n_f_i_g_u_r_e [<_c_o_u_n_t>]
 
Display or set the number of configuration  requests  sent.   The
default is 10.
 
_3._4_1._2._6._2.  _p_p_p <_i_f_a_c_e> _l_c_p _t_r_y _f_a_i_l_u_r_e [<_c_o_u_n_t>]
 
Display or set the number of bad configuration  requests  allowed
from the remote.  The default is 5.
 
_3._4_1._2._6._3.  _p_p_p <_i_f_a_c_e> _l_c_p _t_r_y _t_e_r_m_i_n_a_t_e [<_c_o_u_n_t>]
 
Display or set the number of  termination  requests  sent  before
shutdown.  The default is 2.
 
_3._4_1._3.  _p_p_p <_i_f_a_c_e> _i_p_c_p ...
 
These commands are used for the IPCP [Internet  Protocol  Control
Protocol] configuration.
 
The close, open, timeout and try sub-commands  are  identical  to
the LCP (described above).
 
_3._4_1._3._1.  _p_p_p <_i_f_a_c_e> _i_p_c_p _l_o_c_a_l ...
 
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._4_1._3._1._1.  _p_p_p <_i_f_a_c_e> _i_p_c_p _l_o_c_a_l _a_d_d_r_e_s_s [  <_h_o_s_t_i_d>  |  _a_l_l_o_w
[_o_n | _o_f_f] ]
 
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._4_1._3._1._2.  _p_p_p  <_i_f_a_c_e>  _i_p_c_p  _l_o_c_a_l  _c_o_m_p_r_e_s_s  [  _t_c_p  <_s_l_o_t_s>
[<_f_l_a_g>] | _n_o_n_e | _a_l_l_o_w [_o_n | _o_f_f] ]
 
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.
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 23 -
 
 
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._4_1._3._2.  _p_p_p <_i_f_a_c_e> _i_p_c_p _r_e_m_o_t_e ...
 
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._4_1._4.  _p_p_p <_i_f_a_c_e> _p_a_p ...
 
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._4_1._4._1.  _p_p_p <_i_f_a_c_e> _p_a_p _u_s_e_r [ <_u_s_e_r_n_a_m_e> [<_p_a_s_s_w_o_r_d>] ]
 
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._4_1._5.  _p_p_p <_i_f_a_c_e> _t_r_a_c_e [<_f_l_a_g_s>]
 
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._4_2.  _p_s
 
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
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 24 -
 
 
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.
 
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._4_3.  _p_w_d [<_d_i_r_n_a_m_e>]
 
An alias for the cd command.
 
_3._4_4.  _r_e_c_o_r_d [_o_f_f | <_f_i_l_e_n_a_m_e>]
 
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._4_5.  _r_e_m_o_t_e [-_p <_p_o_r_t>] [-_k  <_k_e_y>]  [-_a  <_k_i_c_k_a_d_d_r>]  <_h_o_s_t_i_d>
_e_x_i_t | _r_e_s_e_t | _k_i_c_k
 
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
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
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 25 -
 
 
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
 
 
 
_3._4_6.  _r_e_m_o_t_e -_s <_k_e_y>
 
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 _n_o_t yet
supported by any other TCP/IP implementation.
 
_3._4_7.  _r_e_n_a_m_e <_o_l_d_f_i_l_e_n_a_m_e> <_n_e_w_f_i_l_e_n_a_m_e>
 
Rename oldfilename to newfilename.
 
_3._4_8.  _r_e_s_e_t [<_s_e_s_s_i_o_n>]
 
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._4_9.  _r_i_p ...
 
These commands are used for the RIP service.
 
_3._4_9._1.  _r_i_p _a_c_c_e_p_t <_g_a_t_e_w_a_y>
 
Remove the specified gateway from the RIP filter table,  allowing
future broadcasts from that gateway to be accepted.
 
_3._4_9._2.  _r_i_p _a_d_d <_h_o_s_t_i_d> <_s_e_c_o_n_d_s> [<_f_l_a_g_s>]
 
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
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 26 -
 
 
"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
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._4_9._3.  _r_i_p _d_r_o_p <_d_e_s_t>
 
Remove an entry from the RIP broadcast table.
 
_3._4_9._4.  _r_i_p _m_e_r_g_e [_o_n | _o_f_f]
 
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
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 27 -
 
 
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._4_9._5.  _r_i_p _r_e_f_u_s_e <_g_a_t_e_w_a_y>
 
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.
 
_3._4_9._6.  _r_i_p _r_e_q_u_e_s_t <_g_a_t_e_w_a_y>
 
Send a RIP Request packet to the specified gateway, causing it to
reply with a RIP Response packet containing its routing table.
 
_3._4_9._7.  _r_i_p _s_t_a_t_u_s
 
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._4_9._8.  _r_i_p _t_r_a_c_e [_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._5_0.  _r_m_d_i_r <_d_i_r_n_a_m_e>
 
Remove a sub-directory from the current working directory.
 
_3._5_1.  _r_o_u_t_e
 
With no arguments, route displays the IP routing table.
 
_3._5_1._1.   _r_o_u_t_e  _a_d_d  <_d_e_s_t__h_o_s_t_i_d>[/_b_i_t_s]  |   _d_e_f_a_u_l_t   <_i_f_a_c_e>
[<_g_a_t_e_w_a_y__h_o_s_t_i_d> [<_m_e_t_r_i_c>]]
 
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
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 28 -
 
 
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
 
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).
 
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
 
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 29 -
 
 
_3._5_1._2.  _r_o_u_t_e _a_d_d_p_r_i_v_a_t_e <_d_e_s_t _h_o_s_t_i_d>[/_b_i_t_s] | _d_e_f_a_u_l_t  <_i_f_a_c_e>
[<_g_a_t_e_w_a_y _h_o_s_t_i_d> [<_m_e_t_r_i_c>]]
 
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.
 
_3._5_1._3.  _r_o_u_t_e _d_r_o_p <_d_e_s_t _h_o_s_t_i_d>
 
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._5_2.  _s_e_s_s_i_o_n [<_s_e_s_s_i_o_n #>]
 
Without arguments, displays the list of current sessions, includ-
ing  session  number, remote TCP or AX.25 address and the address
of the TCP or AX.25 control block.  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 _c_o_n_-
_v_e_r_s_e 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  converse with the remote user as though the session
had been locally initiated.
 
_3._5_3.  _s_h_e_l_l
 
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._5_4.  _s_m_t_p ...
 
These commands are used for the Simple Message Transport Protocol
service (that is, mail).
 
_3._5_4._1.  _s_m_t_p _g_a_t_e_w_a_y [<_h_o_s_t_i_d>]
 
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._5_4._2.  _s_m_t_p _k_i_c_k
 
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.
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 30 -
 
 
_3._5_4._3.  _s_m_t_p _m_a_x_c_l_i_e_n_t_s [<_c_o_u_n_t>]
 
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.
 
_3._5_4._4.  _s_m_t_p _t_i_m_e_r [<_s_e_c_o_n_d_s>]
 
Displays or sets the interval between scans of the outbound  mail
queue. For example, smtp timer 600 will cause the system to check
for outgoing mail every 10 minutes and attempt  to  deliver  any-
thing  it  finds, subject of course to the smtp maxclients limit.
Setting a value of zero disables queue scanning altogether,  note
that  this  is  the default!  This value is recommended for stand
alone IP gateways that never handle mail, since it saves wear and
tear on the floppy disk drive.
 
_3._5_4._5.  _s_m_t_p _t_r_a_c_e [<_v_a_l_u_e>]
 
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._5_5.  _s_o_c_k_e_t [<_s_o_c_k_e_t #>]
 
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._5_6.  _s_t_a_r_t _a_x_2_5 | _d_i_s_c_a_r_d | _e_c_h_o | _f_t_p | _n_e_t_r_o_m | _r_e_m_o_t_e | _s_m_t_p
| _t_e_l_n_e_t | _t_t_y_l_i_n_k
 
Start the specified Internet server, allowing  remote  connection
requests.
 
_3._5_7.  _s_t_o_p _a_x_2_5 | _d_i_s_c_a_r_d | _e_c_h_o | _f_t_p | _n_e_t_r_o_m | _r_e_m_o_t_e |  _s_m_t_p
| _t_e_l_n_e_t | _t_t_y_l_i_n_k
 
Stop the specified Internet server, rejecting any further  remote
connect  requests.  Existing  connections are allowed to complete
normally.
 
_3._5_8.  _t_c_p ...
 
These commands are used for  the  Transmission  Control  Protocol
service.
 
_3._5_8._1.  _t_c_p _i_r_t_t [<_m_i_l_l_i_s_e_c_o_n_d_s>]
 
Display  or  set  the  initial  round  trip  time  estimate,   in
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 31 -
 
 
milliseconds,  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
started in order for it to have effect on incoming connections.
 
TCP also keeps a _c_a_c_h_e of 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._5_8._2.  _t_c_p _k_i_c_k <_t_c_b__a_d_d_r>
 
If there is unacknowledged data on the send queue of  the  speci-
fied TCB, this command forces an immediate retransmission.
 
_3._5_8._3.  _t_c_p _m_s_s [<_s_i_z_e>]
 
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._5_8._4.  _t_c_p _r_e_s_e_t <_t_c_b__a_d_d_r>
 
Deletes the TCP control block at the specified address.
 
_3._5_8._5.  _t_c_p _r_t_t <_t_c_b__a_d_d_r> <_m_i_l_l_i_s_e_c_o_n_d_s>
 
Replaces the automatically computed round trip time in the speci-
fied TCB with the rtt in milliseconds.  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._5_8._6.  _t_c_p _s_t_a_t_u_s [<_t_c_b__a_d_d_r>]
 
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.
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 32 -
 
 
_3._5_8._7.  _t_c_p _w_i_n_d_o_w [<_s_i_z_e>]
 
Displays or sets the default receive window size in bytes  to  be
used  by  TCP when creating new connections. Existing connections
are unaffected.
 
_3._5_9.  _t_e_l_n_e_t <_h_o_s_t_i_d>
 
Creates a Telnet session to the specified host  and  enters  con-
verse mode.
 
_3._6_0.  _t_i_p <_i_f_a_c_e>
 
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._6_1.  _t_r_a_c_e [<_i_f_a_c_e> [_o_f_f | <_b_t_i_o> [<_t_r_a_c_e_f_i_l_e>]]]
 
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.
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 33 -
 
 
_3._6_2.  _u_d_p _s_t_a_t_u_s
 
Displays the status of all UDP receive queues.
 
_3._6_3.  _u_p_l_o_a_d [<_f_i_l_e_n_a_m_e>]
 
Opens filename and sends it on the current session as  though  it
were typed on the terminal.
 
_3._6_4.  _w_a_t_c_h
 
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._6_5.  ?
 
Same as the help command.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 34 -
 
 
_4.  _A_t_t_a_c_h _C_o_m_m_a_n_d_s
 
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.  <_b_u_f_s_i_z_e>
 
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.  <_i_o_a_d_d_r>
 
The base address of the interface's control registers, in hex.
 
_4._0._3.  <_v_e_c_t_o_r>
 
The interface's hardware interrupt (IRQ) vector, in hex.
 
_4._0._4.  <_i_f_a_c_e>
 
The name (an arbitrary character string) to be assigned  to  this
interface.  It  is used to refer to the interface in ifconfig and
route commands and in trace output.
 
_4._0._5.  <_m_t_u>
 
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).
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 35 -
 
 
_4._0._6.  <_s_p_e_e_d>
 
The speed in bits per second (eg. 2400).
 
_4._1.  _a_t_t_a_c_h _3_c_5_0_0 <_i_o_a_d_d_r> <_v_e_c_t_o_r> _a_r_p_a  <_i_f_a_c_e>  <_q_l_e_n>  <_m_t_u>
[<_i_p__a_d_d_r>]
 
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.  _a_t_t_a_c_h _a_s_y <_i_o_a_d_d_r> <_v_e_c_t_o_r>  _a_x_2_5  |  _n_r_s  |  _p_p_p  |  _s_l_i_p
<_i_f_a_c_e> <_b_u_f_s_i_z_e> <_m_t_u> <_s_p_e_e_d> [<_c_r_v>]
 
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.  _a_x_2_5
 
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.  _n_r_s
 
Use the NET/ROM asynchronous framing technique for  communication
with a local NET/ROM TNC.
 
_4._2._3.  _p_p_p
 
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.
 
_4._2._4.  _s_l_i_p
 
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.  <_c_r_v>
 
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
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 36 -
 
 
valid only for SLIP.
 
_4._3.  _a_t_t_a_c_h _d_r_s_i <_i_o_a_d_d_r> <_v_e_c_t_o_r> _a_x_2_5 <_i_f_a_c_e> <_b_u_f_s_i_z_e>  <_m_t_u>
<_c_h__a__s_p_e_e_d> <_c_h__b__s_p_e_e_d>
 
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.  _a_t_t_a_c_h _e_a_g_l_e <_i_o_a_d_d_r> <_v_e_c_t_o_r> _a_x_2_5 <_i_f_a_c_e> <_b_u_f_s_i_z_e> <_m_t_u>
<_s_p_e_e_d>
 
WA3CVG/NG6Q driver for the Eagle Computer card (Zilog 8530).
 
_4._5.  _a_t_t_a_c_h _h_a_p_n <_i_o_a_d_d_r> <_v_e_c_t_o_r> _a_x_2_5 <_i_f_a_c_e> <_b_u_f_s_i_z_e>  <_m_t_u>
_c_s_m_a | _f_u_l_l
 
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.  _a_t_t_a_c_h _h_s <_i_o_a_d_d_r> <_v_e_c_t_o_r> _a_x_2_5  <_i_f_a_c_e>  <_b_u_f_s_i_z_e>  <_m_t_u>
<_k_e_y_u_p__d_e_l_a_y> <_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  byte  time  intervals.  The p value specifies the transmitter
persistence value in the range 1-255; the corresponding slot time
is fixed at one hardware clock tick, about 55 ms on the PC.
 
As with the other 8530 drivers, this driver actually attaches two
interfaces, one for each 8530 channel.
 
_4._7.  _a_t_t_a_c_h _p_a_c_k_e_t <_i_n_t_v_e_c> <_i_f_a_c_e> <_t_x_q_l_e_n> <_m_t_u>
 
Driver for use with separate software  "packet  drivers"  meeting
the FTP Software, Inc, Software Packet Driver specification.  The
driver must have already been installed before the attach command
is given. Packet drivers in the Ethernet, ARCNET, SLIP, SLFP, and
KISS/AX25 classes are supported.
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 37 -
 
 
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.  _a_t_t_a_c_h  _p_c_1_0_0  <_i_o_a_d_d_r>  <_v_e_c_t_o_r>  _a_x_2_5  <_i_f_a_c_e>  <_b_u_f_s_i_z_e>
<_s_p_e_e_d>
 
Driver for the PACCOMM PC-100  (Zilog  8530)  card.   Only  AX.25
operation is supported.
 
_4._9.  _a_t_t_a_c_h _s_c_c <_d_e_v_i_c_e_s> _i_n_i_t <_a_d_d_r>  <_s_p_a_c_i_n_g>  <_A_o_f_f>  <_B_o_f_f>
<_D_a_t_a_o_f_f> <_i_n_t_a_c_k> <_v_e_c> [_p|_r]<_c_l_o_c_k> [<_h_d_w_e>] [<_p_a_r_a_m>]
 
PE1CHL driver to initialize a generic SCC (8530) interface  board
prior to actually attaching it. The parameters are as follows:
 
_4._9._1.  <_d_e_v_i_c_e_s>
 
The number of SCC chips to support.
 
_4._9._2.  <_a_d_d_r>
 
The base address of the first SCC chip (hex).
 
_4._9._3.  <_s_p_a_c_i_n_g>
 
The spacing between the SCC chip base addresses.
 
_4._9._4.  <_A_o_f_f>
 
The offset from a chip's base address to its  channel  A  control
register.
 
_4._9._5.  <_B_o_f_f>
 
The offset from a chip's base address to its  channel  B  control
register.
 
_4._9._6.  <_D_a_t_a_o_f_f>
 
The offset from each  channel's  control  register  to  its  data
register.
 
_4._9._7.  <_i_n_t_a_c_k>
 
The address of the INTACK/Read Vector port. If none, specify 0 to
read from RR3A/RR2B.
 
_4._9._8.  <_v_e_c>
 
The CPU interrupt vector for all connected SCCs.
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 38 -
 
 
_4._9._9.  <_c_l_o_c_k>
 
The clock frequency (PCLK/RTxC) of all  SCCs  in  hertz.   Prefix
with 'p' for PCLK, 'r' for RTxC clock (for baudrate gen).
 
_4._9._1_0.  <_h_d_w_e>
 
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._1_1.  <_p_a_r_a_m>
 
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._1_0.  _a_t_t_a_c_h _s_c_c <_c_h_a_n> _s_l_i_p | _k_i_s_s | _n_r_s | _a_x_2_5  <_i_f_a_c_e>  <_m_t_u>
<_s_p_e_e_d> <_b_u_f_s_i_z_e> [<_c_a_l_l>]
 
Attach an initialized SCC port to the system. The parameters  are
as follows:
 
_4._1_0._1.  <_c_h_a_n>
 
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._1_0._2.  _s_l_i_p | _k_i_s_s | _n_r_s | _a_x_2_5
 
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._1_0._3.  <_s_p_e_e_d>
 
The interface speed in bits per second (eg. 1200).   Prefix  with
'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.
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 39 -
 
 
_4._1_1.  _A_t_t_a_c_h _E_x_a_m_p_l_e_s
 
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
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 40 -
 
 
_5.  _F_T_P _S_u_b_c_o_m_m_a_n_d_s
 
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.  _d_i_r [<_f_i_l_e> | <_d_i_r_e_c_t_o_r_y> [<_l_o_c_a_l _f_i_l_e>]]
 
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
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.  _g_e_t <_r_e_m_o_t_e _f_i_l_e> [<_l_o_c_a_l _f_i_l_e>]
 
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.  _h_a_s_h
 
A synonym for the verbose 3 command.
 
_5._4.  _l_s [<_f_i_l_e> | <_d_i_r_e_c_t_o_r_y> [<_l_o_c_a_l _f_i_l_e>]]
 
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.  _m_g_e_t <_f_i_l_e> [<_f_i_l_e> ...]
 
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.  _m_k_d_i_r <_r_e_m_o_t_e _d_i_r_e_c_t_o_r_y>
 
Creates a directory on the remote machine.
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 41 -
 
 
_5._7.  _m_p_u_t <_f_i_l_e> [<_f_i_l_e> ...]
 
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.  _p_u_t <_l_o_c_a_l _f_i_l_e> [<_r_e_m_o_t_e _f_i_l_e>]
 
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.  _r_m_d_i_r <_r_e_m_o_t_e _d_i_r_e_c_t_o_r_y>
 
Deletes a directory on the remote machine.
 
_5._1_0.  _t_y_p_e [_a | _i | _l <_b_y_t_e_s_i_z_e>]
 
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  _i_m_a_g_e,  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._1_1.  _v_e_r_b_o_s_e [_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.
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 42 -
 
 
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.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 43 -
 
 
_6.  _D_i_a_l_e_r _S_u_b_c_o_m_m_a_n_d_s
 
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:
 
        # 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7"
        wait 45000 "CONNECT " speed
        wait 2000
        # PAD specific initialization
        send "7"
        wait 15000 "Terminal ="
        send "ppp7"
        wait 10000 "70
 
 
_6._0._1.  _c_o_n_t_r_o_l _d_o_w_n | _u_p
 
Control asy interface.  The down option drops DTR and  RTS.   The
up option asserts DTR and RTS.
 
_6._0._2.  _s_e_n_d "_s_t_r_i_n_g"
 
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).
 
_6._0._3.  _s_p_e_e_d [ _9_6_0_0 | _4_8_0_0 | _2_4_0_0 | _1_2_0_0 | _3_0_0 ]
 
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.  _w_a_i_t <_m_i_l_l_i_s_e_c_o_n_d_s> [ "_t_e_s_t _s_t_r_i_n_g" ] [ _s_p_e_e_d ]
 
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).
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 44 -
 
 
Finally, if the _s_p_e_e_d parameter is  specified,  the  dialer  will
continue  to  read characters until a non-digit is detected.  The
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.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 45 -
 
 
_7.  _T_h_e /_f_t_p_u_s_e_r_s _F_i_l_e
 
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  _n_o 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
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.
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 46 -
 
 
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.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 47 -
 
 
_8.  _T_h_e domain.txt _F_i_l_e
 
Net.exe translates domain names (eg.  "pc.ka9q.ampr.org")  to  IP
addresses  (eg.  128.96.160.3)  through  the  use  of an Internet
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 _c_l_a_s_s of the record.  It means _I_n_t_e_r_n_e_t, and it will be
found  in all entries.  A is the _t_y_p_e of the record, and it means
that this is an _a_d_d_r_e_s_s  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  _c_a_n_o_n_i_c_a_l)  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
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 48 -
 
 
This is the _t_i_m_e-_t_o-_l_i_v_e 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
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 _T_T_L 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 NS  (name  server)  and  SOA
(start  of authority) may appear in domain.txt from remote server
responses. These are  not  currently  used  by  net.exe  but  are
retained  for  future development (such as the incorporation of a
domain name server into net.exe itself).
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 49 -
 
 
_9.  _S_e_t_t_i_n_g _B_u_f_s_i_z_e, _P_a_c_l_e_n, _M_a_x_f_r_a_m_e, _M_T_U, _M_S_S _a_n_d _W_i_n_d_o_w
 
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.  _H_a_r_d_w_a_r_e _P_a_r_a_m_e_t_e_r_s
 
 
_9._1._1.  _B_u_f_s_i_z_e
 
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.  _A_X_2_5 _P_a_r_a_m_e_t_e_r_s
 
_9._2._1.  _P_a_c_l_e_n
 
Paclen limits the size of the data field  in  an  AX.25  I-frame.
This  value  does  _n_o_t 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.
 
_9._2._2.  _M_a_x_f_r_a_m_e
 
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 _n_o_t apply to
unconnected mode.
 
The default value of maxframe in net.exe is 1 frame.
 
_9._3.  _I_P _a_n_d _T_C_P _P_a_r_a_m_e_t_e_r_s
 
_9._3._1.  _M_T_U
 
The MTU (Maximum Transmission Unit)  is  an  interface  parameter
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 50 -
 
 
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 _f_r_a_g_m_e_n_t_s.  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.  _M_S_S
 
MSS (Maximum Segment Size) is a TCP-level parameter  that  limits
the  amount of data that the _r_e_m_o_t_e 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.  _W_i_n_d_o_w
 
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
the _e_f_f_e_c_t_i_v_e _w_i_n_d_o_w.  This is the smaller  of  two  values:  the
window advertised by the remote TCP minus the unacknowledged data
in flight, and the _c_o_n_g_e_s_t_i_o_n _w_i_n_d_o_w, an  automatically  computed
time-varying estimate of how much data the network can handle.
 
The default value of Window is 2048 bytes.
 
_9._4.  _D_i_s_c_u_s_s_i_o_n
 
 
_9._4._1.  _I_P _F_r_a_g_m_e_n_t_a_t_i_o_n _v_s _A_X._2_5 _S_e_g_m_e_n_t_a_t_i_o_n
 
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
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 51 -
 
 
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  _t_r_a_n_s_p_a_r_e_n_t  _f_r_a_g_m_e_n_t_a_-
_t_i_o_n,  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.  _S_e_t_t_i_n_g _p_a_c_l_e_n _a_n_d _b_u_f_s_i_z_e
 
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
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
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 52 -
 
 
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
currently  fixed  in  size  to 2048 bytes and this can be changed
only by editing config.h and recompiling NOS.  This  limits  buf-
size;  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.  _S_e_t_t_i_n_g _M_a_x_f_r_a_m_e
 
For best performance on a  half-duplex  radio  channel,  maxframe
should always be set to 1. The reasons are explained in the paper
_L_i_n_k _L_e_v_e_l _P_r_o_t_o_c_o_l_s _R_e_v_i_s_i_t_e_d by  Brian  Lloyd  and  Phil  Karn,
which  appeared  in the proceedings of the ARRL 5th Computer Net-
working Conference in 1986.
 
_9._4._4.  _S_e_t_t_i_n_g _M_T_U
 
TCP/IP header overhead considerations similar  to  those  of  the
AX.25 layer when setting paclen apply when choosing an MTU.  How-
ever, 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 _c_o_n_n_e_c_t_i_o_n_s are automatically segmented  into  I-frames  no
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 53 -
 
 
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.  _S_e_t_t_i_n_g _M_S_S
 
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
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.
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 54 -
 
 
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.  _S_e_t_t_i_n_g _W_i_n_d_o_w
 
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 incom-
ing data from an active connection as soon as it arrives, thereby
quickly freeing the buffer memory.  However, it  is  possible  to
run  net.exe  out  of  memory  if  excessive TCP window sizes are
advertised and either the applications go to  sleep  indefinitely
(eg.  suspended Telnet sessions) or a lot of out-of-sequence data
arrives.  It is wise to keep an eye on the  amount  of  available
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.
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991
 
 
 
 
 
                           - 55 -
 
 
_9._5.  _S_u_m_m_a_r_y
 
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.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
updated by Bill SimpsonMarch 7, 1991           March 3, 1991