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OVERVIEW.X1H
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1992-11-02
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TheNet X-1H
Overview of Operation
1. INTRODUCTION
This paper introduces the main features of TheNet X-1H. This
is an update to the previous paper on version X-1F, as the
only differences to X-1G were the correction of 3 bugs.
The bugs were :
When using a number of tncs crosslinked to a BPQ switch
there was a small probability of lockup. This has been
cured.
ICMP_ECHO would return 4 characters only rather than to
echo all the characters in the ICMP_ECHO frame.
The ROUTES list would show incorrect aliases under
certain circumstances.
The software is a derivative of TheNet 1.01 by NORD><LINK.
Additional commands and bug fixes have been included in the
release.
If your reaction is 'What I really want is ......', then
please read on anyway, especially section 6.
2. STRUCTURE
One of the problems to extending TheNet is the 32 K EPROM
limitation imposed by the architecture of TNC2 clones. The
solution to this is to implement bankswitching. For the BSX2
TNC and similar TNC2 clones, this can be achieved by the
addition of a single wire as detailed in the bankswitch
modification file. This is at the expense of the HIGH and
LOW commands, and if anyone misses those commands, a version
is available that implements them but required cut & stap
mods to the TNC.
3. NEW COMMANDS
The following commands have been added to the release
BYE
BBS
HOST
STATS
MHEARD
MODE
MANAGER
AUDIT
TALK
CALIBRATE
LINKS
ACL
CLOSEDOWN
BTEXT
DXCLUSTER
HELP
CTEXT
ALIAS
BBSALIAS
HOSTALIAS
DXCALIAS
QUIT
IPROUTE
ARP
IPSTATS
IPADDRESS
IPBROADCAST
UI
The following commands have been changed
CQ
NODES
RESET
the <escape> commands
SYSOP
The following features have been added to the code
An Internet Router
Ability to respond to three additional aliases
A CWID keyer
The command processor has been extended
KISS mode operation on the RS232 port
HOST mode support on the RS232 port
Remote configuration of all parameters
Additional textual help messages
In addition, a number of small changes have been implemented
to satisfy the needs of specialist situations such as the
ability to digi beacon packets.
Network management in this context does not just mean
'setting parameters remotely'. It means the ability to set,
read and interpret various monitors and diagnostic tools.
Version X-1C included the first part of the network
management, the MANAGER privilege and the AUDIT process.
Version X-1D extends the auditing and statistics
significantly including internal CPU monitors. Version X-1E
includes most of the additions that are planned, and version
2 will complete the functions. No other release before
version 2 was planned, but the need to produce a version
with an IP router has prompted this release. The opportunity
to experiment with additional features has therefore been
taken. The next version will hopefully include significant
changes attributable to Hayden Bate G8AMD.
3.1 BYE or QUIT
There are no parameters to these commands. When entered,
they terminate the session. Both commands do the same thing.
3.2 BBS
The syntax of the command is :
BBS [ * | ? | callsign ]
With no parameter, the command connects to a station
previously specified by the sysop. Setting the BBS
destination is done by the use of the BBS command with a
callsign as a second parameter. Setting the BBS to allow
this may only be done by a sysop. The '*' option may also
only be executed by the sysop, this command clears a
previously specified BBS.
The '?' option ( or any text if not sysop ), prints out the
current BBS station setting.
If no BBS is set, the command issues an error message if it
is invoked with no other parameters.
The idea of this command is that, like with the 'bbs'
command of the 'BPQ software, a user may connect to the
local BBS from the node.
3.3 HOST
The syntax of the command is :
HOST [ * | ? | callsign ]
This command is very similar to the 'BBS' command. It allows
connection to a local host, BBS or other server. The
difference however, is that as long as the TNC is not in
'crosslink' mode ( ie pin 23 on the RS232 port is high ),
and if a callsign is not set, the 'host' command connects to
the local port.
The idea of this command is that, like with the 'bbs'
command of the 'BPQ software, a user may connect to the
local BBS, another node or server from this node. For
example, if a print server were connected to the node in
'host' mode, this command would allow connection to it (
like the 'connect' command with no other parameter ). In
KISS mode, setting a callsign or node alias allows
connection to that system.
3.4 STATS
The STATS command has no parameters. It prints a number of
internal TNC statistics. In this version, this is limited to
the level 1 stats of the radio channel and the internal
clocks, the level 2 ( AX.25 ), 3 and 4 statistics, and the
CPU health checks.
For level 1, six pairs of numbers are printed, corresponding
to the percentage of time the transmitter was on followed by
the percentage of time the receiver DCD was on, for each of
the last six 10 minute periods. The data is presented most
recent period first. Two pairs of numbers are then displayed
showing the transmitter underrun and receiver overrun. These
are formatted as per the level 2 stats with port 0 followed
by port 1 for the current hour followed by the totals for
the previous hour. In the case of the RS232 port, underruns
are not possible, and an additonal error ( framing ) is
included. The RX overrun includes overruns and framing
errors.
For level 2, the following are displayed :
Frame checksum errors
Total packets heard
Total packets received by the node ( ie sent to it )
Total packets sent by the node
Total receiver not ready packets sent
Total reject packets sent
Total receiver not ready packets received
Total reject packets received
Total number of link timeouts
For each of the level 2 statistics, four numbers are shown.
The first two are cumulative totals over the period of one
hour, incrementing in real time. The last two are the totals
for the previous hour. Each pair of numbers is the total for
the radio port followed by the total for the RS232 (
crosslink ) port.
For checksum errors, port 0 shows CRC errors and port 1
shows ( when in 'crosslink' protocol mode only ), checksum
errors. As HDLC errors can be triggered by noise, acceptance
of CRC errors is conditioned by the state of the DCD line.
If DCD is on and an error is signalled, it will be added to
the count. This reduces the false counts, but does not
eliminate them. Distant stations that keep the squelch open
( just ) without being properly heard will result in lots of
apparent errors.
For level 3, the number of level 4 frames gatewayed between
nodes is displayed.
For level 4, the number of transport frames sent and
received by the node are shown.
For level 3 and 4 statistics, two numbers are shown. The
first is the number of frames accumulating for this hour,
and the second number is the total number of frames for the
previous hour.
For CPU health checking, two statistics are shown, the CPU
loading and the buffer usage. Each looks like the level 1
stats with 6 numbers corresponding to the last six 10 minute
periods.
The CPU loading shows the number of times, divided by 100,
that the CPU makes it around its basic internal scheduler.
For a node just switched on, receiving nothing, this will be
about 470 ish for a 4.9 MHz clock. With lots of nodes, a
heard list of 20 stations and 70-80% activity on the radio
channel for it to listen to, this can drop to about 350ish.
If it drops to double figures, worry, as the CPU is
beginning to thrash. At low double figures, the CPU is
pretty much working flatout. Time to up its clock rate !.
The BUFFERS statistic shows the minimum number of free
buffers that the software had available to it during the
last six 10 minute period. This indicates whether the TNC is
failing to deliver data passed to it for onwards
transmission, as well as how much data is backed up waiting.
Additional stats needed to analyse this properly are not yet
being collected.
The display also shows the elapsed time since the last
warmstart followed by the running time since the last
coldstart. Each number is the number of hours of operation.
3.5 MODE
This command is similar to the PARAM command.
It allows a number of other features of the software to be
configured remotely. It removes the need for most of the
host mode <escape> commands.
The following parameters may be configured :
The host mode
The CWID send period
The CWID keyer speed
The port nodes broadcast control
The crosslink / kiss control
The Tx delay
The full duplex flag
The rs232 port node broadcast interval
The node broadcast algorithm
The beacon period
The 'connect' redirector
The 'help message enable' flags
The 'hash' node broadcast port control
Whether the node will listen for the extra aliases
In operation, it behaves just like the PARAM command.
The parameters are as follows :
3.5.1 Host mode control
This parameter controls the 'host' mode. This is the mode of
operation of the RS232 port when pin 23 is 'high'
The valid values are 0 or 1.
In mode 0, the port operates as per the standard node
specification. Mode 1 is designed to allow connection to
hosts or modems or similar equipment that expects a 'CD'
type of signal to signify that an incoming / outgoing
connection is called for.
In mode 1, the <escape> C and <escape> D commands are
disabled and the other <escape> commands do not operate when
connected. Instead, hardware handshakes are used to control
conections to and from the TNC.
The TNC monitors pin 20 to determine the state of the host,
and signals state changes to the host with pin 5. When an
incoming connect request is received ( by the 'c' command
with no parameters or by the 'host' command ), the TNC
raises pin 5 to signal the connection and expects pin 20 to
change state in response.
When the host wishes to place connect to the TNC, it signals
on pin 20 and the TNC responds with by changing the state of
pin 5.
It handles disconnects in a similar manner. Either the node
or the host may initiate disconnects.
This mode is experimental, changes may be made to its
operation. It is designed for modems, print servers or hosts
such as UNIX system tty login drivers.
3.5.2 CWID control
The next two parameters control the CWID keyer.
The first parameter is the CWID repeat period in seconds.
Valid values are 0 to 3600. 0 disables it but do not set it
below 120 apart from to disable it.
The second parameter controls the keyer speed. Specifically,
it sets the number of 10 millisecond periods per dot and per
inter symbol delay.
The speed of sending is 120/n, so setting n to 6 gives 20
wpm. Valid values are 4 to 10, corresponding to speeds of 30
and 12 wpm respectively.
3.5.3 Node broadcast control
This parameter allows control to be exercised over which
ports nodes broadcasts are sent. Valid settings are 0 - 3.
Value 0 disables node broadcasts. Value 3 ( the default )
works as normal. A value of 1 enables broadcasts on the HDLC
port only whilst a value of 2 enables broadcasts on the
crosslink port only.
3.5.4 Crosslink / kiss
This parameter is used to set the communications protocol used
on the crosslink port when pin 23 is tied low.
The valid values are 0, 1, 2 or 3
Mode 0 - standard crosslink protocol enabled
Mode 1,2,3 - use KISS instead of crosslink.
In mode 1, KISS simply replaces the crosslink protocol
In mode 2, packets received from the radio part that are not
intended for the node are copied to the RS232 port in KISS
mode. Similarly packets received on the RS232 port that are
not intended for the node are sent to the radio port.
In mode 3, all packets received on one port are copied to
the other port as well as being analysed by the node.
These modes are not simply KISS implementations that replace
the node, they run with the node.
Mode 2 is designed to allow a KISS application and a node to
share a radio without interference with each other. The
point is that the PC TCPIP system can be switched off whilst
leaving the node running to allow others to use it.
Mode 3 is a debugging mode. One problem when faultfinding on
a node is that it is impossible to see what the node is
seeing on the channel without replacing the rom. By setting
this mode, it is possible to connect a KISS application to
the RS232 port and observe what the node is seeing.
Mode 3 is also designed to allow a PC running AXSTATS to be
connected to the RS232 port to allow logging and analysis of
channel performance from the node itself.
3.5.5 Tx keyup delay
This parameter sets the TX keyup delay in 10's of
milliseconds. This was previously done using an escape
command.
3.5.6 Full Duplex
This parameter sets or clears the full duplex control flag.
This was previously done using an escape command.
3.5.7 RS232 nodes broadcast interval
When a crosslinked TNC is reset, it takes some time to learn
about the nodes that the other TNCs can hear. Also, nodes
heard by one TNC can take an hour to be notified to the
others.
In order to improve this, this parameter may be used to
change the frequency of nodes broadcasts on the RS232 port.
When set to 0, the node operates as normal. When set to a
non zero value, it will broadcast the nodes on the RS232
port at that interval. Hence setting it to 600 would cause
nodes broadcasts at 10 minute periods. The nodes broadcasts
on the radio port will continue to occur at the basic rate
set by the PARAM setting. The obsolescence count will be
decremented at the basic rate, not at the faster RS232 rate.
3.5.8 Node broadcast algorithm
This value controls the algorithm used. Bits within the
value set have significance as shown below.
There is a problem with the nodes broadcast algorithm when
many TNCs are crosslinked on RS232. In order to address this
a variation to the algorithm has been implemented for
experimental purposes. Feedback on its use is requested. Bit
zero affects the HDLC port and bit 1 affects the RS232 port.
When a bit is set to 1, the node broadcast algorithm is
modified so that it will not rebroadcast on the same port a
node heard on that port when the best quality neighbour is
on that port. It makes little sense to use it on the HDLC
port but what the heck, it is implemented for completeness.
The only settings therefore that make sense are 0 and 2.
These correspond to 'normal' and 'modified on the RS232
port' respectively. Setting it to 1 or 3 will result in some
pretty weird effects.
3.5.9 Beacon period
This parameter sets the beacon interval in seconds. In
TheNet 1.01, this was fixed at 10 minutes ( 600 seconds ).
In this version, this parameter may be used to change it
according the the prevailing license conditions.
3.5.10 'Connect' redirector
In TheNet 1.01, when 'connect' is given with no destination
callsign, the node attempted to connect to the local host
port. In a crosslinked system, this vanished down a black
hole. In previous versions of this code, the node attempted
to connect to the station set by the HOST command, only
trying the local host port if no destination was set by
HOST. With this version, the node may be configured to
connect to the station set by the BBS, DXCLUSTER or the HOST
command depending on this parameter. When zero, connect
attempts will go to the HOST station, when set to '1', it
will attempt to connect to the BBS callsign. When set to 2
it will attempt to connect to the DXCLUSTER callsign.
3.5.11 'help message enable' flags
This word controls the sending of help messages, with each
bit of the word controlling a separate function. Currently,
only 4 bits are effective, these being as follows :
BIT FUNCTION
=========================
0 Whether the 'please wait, trying xxxx' operates
1 Whether all commands appear in help for sysop
2 Whether the 'goodbye' message is given
3 Whether a welcome message is enabled ( CTEXT )
4 Whether nodes are shown as 'alias:callsign'
When bit 0 is set, and the BBS, HOST or DXcluster commands
are given, then a message is sent from the node telling the
user that a connect attempt is being made. This does not
affect the 'connect' command itself, unless the command is
given with no parameter as this is then equivalent of the
BBS or HOST command.
When bit 1 is set, and if a sysop gives an incorrect
command, the help screen shows all commands possible,
including those currently disabled ( as by definition they
are not disabled for the sysop ! ).
When bit 2 is set, then the use of the 'bye' command will
solicit a 'goodbye' message from the node.
Bit 3 switches on and off the 'CTEXT' message. When enabled,
and when a CTEXT message is set, then whenever someone
uplinks to the node alias, the ctext message is sent
immediately on connect.
Bit 4 switches the way in which nodes are shown when the
ROUTES command is used. When set to '1', nodes are shown as
'alias:callsign'. When set to 0, they are shown only as
'callsign'.
3.5.12 'hash' node port control
In certain networks ( notably the American ), there is a
need to restrict the propagation of local nodes. This is
done by using node aliases that start with a hash character
( # ) and instructing specific nodes not to broadcast routes
to nodes that start with this character. This parameter does
this by enabling each port to be individually enabled or
disabled in respect to 'hash' node broadcasts. Bit 0
controls the radio port and bit 1 controls the RS232 port.
When one of these bits is set, hash nodes will never be
broadcast on that port.
3.5.13 Extra aliases
If this is set to '1', then the node will listen for ( and
accept uplinks to ) the aliases set in HOSTALIAS, DXCALIAS
and BBSALIAS if they are set. If this parameter is set to
'0', or if the respective aliases are not set, it will do
nothing. If you do not use the aliases, set it to 0 to avoid
wasting processor time.
3.6 MHEARD
The TNC can be instructed to keep a list of the last 'nn'
stations heard, where 'nn' is an integer between 1 and 100.
It can also be disabled. The syntax of the command is :
MHEARD [ nn ]
The parameter is optional and only operates for the sysop.
It sets the maximum length of the list. Setting to zero
disables the function.
The heard list uses free buffers for the list, so a large
setting means less RAM for the node software.
The list is maintained as linked list, with the most
recently heard station first. The display shows the number
of packets heard from that station and the time since it was
last heard, in hours minutes and seconds. In addition, it
shows the port on which the station was heard together with
an indication as to whether the station is a node and / or a
TCP/IP station. It does this by examining the PID byte.
Every hour the list is checked for stations that have not
been heard for 12 hours, and any such stations are removed
from the list.
To disable the internal updating of the list ( and thereby
stop the CPU expending effort on the function ), set the
size to zero rather than just disabling the command as
described in 3.8. Note though that the node will not clear
the list as updates have been disabled, so it will be up to
12 hours before the buffers used are freed. To accelerate
this process, set the size to 1, wait until it has heard a
station ( any one will do ) then set it to zero. This will
free up all but one buffer immediately.
3.7 CQ
When CQ is disabled, the command now reports apologetically
rather than simply ignoring the request.
3.8 ALL COMMANDS
There is often a requirement to be able to disable the
connect command whilst allowing level 3 relaying. This is
achieved by the use of a command qualifier, the syntax of
which is :
CONNECT [ + | - ]
If '-' is entered by the sysop, then the connect command
will politely refuse to work. This can be reversed by the
'+' command.
This has no effect of layer 3 relaying. Also, the BBS and
HOST commands will still allow connections to be made if
they are enabled and set.
Further, the syntax is valid for ALL commands, for example
the CQ command can also be disabled in the same way. Be
careful though. The command is only accepted from the sysop,
so if you disable the sysop and manager commands you will
lock out remote management !.
3.9 NODES
When information on a node that is not known is requested,
the program prints out an error message rather than giving
the names of all known nodes.
When a node entry is made by the sysop, callsign checking is
forced ON rather than being determined by the callsign
checking parameter.
The entire contents of the node table routes may be obtained
by the sysop or manager by the command
NODES * *
This will dump info on all nodes, one node per line, with
the following format:
Alias:call route1 route2 route3
where route1, route2 and route3 comprise the quality,
obsolescense count and port followed by the neighbour
callsign for each of the 3 route entries for that node. If
any of the routes are in use, a chevron will be shown by
that route.
The extended command is only for sysop use as it, like
auditing and conferencing, causes the node to be a source of
a significant amount of data ( dumping a large number of
node details can consume hundreds of buffers !!! ). It is
quite possible that used indiscriminately, it could cause a
warmstart of the node. Be careful.
3.10 RESET
The syntax of the command is now
RESET [ anything-else ]
Entering the reset command alone will do a warmstart. If
any other parameter is entered, a coldstart is performed.
3.11 MANAGER
The MANAGER command gives the user extra privileges. In this
version, this amounts to the ability to receive audit
messages from the node. The level of auditing is set by the
AUDIT command.
The privilege remains in force until cleared by a command
that affects the user state. Specifically, these are,
entering the TALK state, executing the SYSOP command,
entering the MANAGER command and getting the password wrong,
or disconnecting from the node. Failing to get the second
password right when using the closedown command will also
remove the manager privilege.
If the MANAGER command is executed by a user who connected
to the node by a level 4 circuit rather than by a level 2
circuit, and if the level 2 timeout is less than the no
activity timeout, the connection will never timeout as the
clearing and reconnecting of the level 2 circuit will keep
the process alive provided level 2 auditing is enabled. This
allows the operation of the node to be logged remotely and
continuously. Alternatively, if the level 4 timeout is
greater than 10 minutes, level 1 or CPU auditing will keep
it alive if level 2 is switched off. NOTE : I have a nasty
feeling that there is something note quite right - the link
sometimes dies !.
A user with MANAGER privilege also has SYSOP privilige.
3.12 AUDIT
The syntax of the audit command is :
AUDIT [ new-value ]
where new value is an integer value. If no value is given,
or the user does not have SYSOP status, the current mask
value is displayed. Otherwise, the mask is updated and the
new value displayed.
The mask controls the auditing of various events in the
node. Not all values are used yet, but those that are, are :
BIT USE
============================================
0 Level 1 statistics on 10 minute updates
1 Level 2 connects & disconnects
2 reserved for future use
3 Level 4 connects & disconnects
4 Level 7 limited events ( use of sysop )
5 Full level 7 auditing
6 CPU auditing messages ( 10 minute updates )
It is suggested that the usual settings can simply be 0 or
255.
For level 1, messages are sent every 10 minutes showing the
percentage of time that the receiver detected carrier and
the percentage of time that the transmitter was on.
At level 2 & 4, the messages are of all connects and
disconnects, shown in 4 different ways :
C Connect message received by node
CA Connect message sent / Acknowledge received
D Disconnect message received by node
DA Disconnect message sent / Acknowledge received
In each case, 2 callsigns are shown. At level 2 these are
the source and destination of the AX.25 link. At level 4, it
is the remote node callsign and user callsign. Each message
is preceded by an indication of the source of the message,
such as "L2" or "L4".
At level 7, with bit 4 set and bit 5 clear, the only event
currently audited is the use of the Sysop command, either
directly or via the manager command. If bit 5 is set, then
all commands given to the switch are audited, preceded by
the callsign of the user who entered the command.
Bit 6 controls CPU health check auditing. If set, then
whenever the internal CPU statistics are updated, messages
are sent showing the CPU processor loading total and the
minimum buffers level ( see STATS for more information ).
The audit mask value should be set to 0 when not actually
being used. Do not leave it set to another value as this
wastes processor time. Note also that full auditing on a
busy node makes things worse. Treat it as a debugging
feature !.
3.13 TALK
Talk is a conferencing command. It allows a number of
stations to hold a simultaneous conference ( a bit like the
CONFERENCE command of a DX cluster ). There is only one
conference, and stations may connect to it by connecting to
the node and issuing the TALK command. It may be exited by
disconnecting or issuing the command '/EXIT' at the start of
a line. ( /EXIT may be abbreviated to /EX, and it is not
case sensitive ).
Each line sent by a user is copied to all other users in the
conference, preceded by the callsign of the user.
Whenever a new station enters the conference, or a station
leaves the conference using the '/EXIT' command, the other
conference users get a message informing them of the event.
These status messages are sent with the callsign of the node
rather than the user.
Finally, when entering the TALK command, a message may be
sent to all those users who are connected to the node but
not otherwise doing anything. For example if GxABC enters
the line
TALK Hello fred, can I have a chat, type 'TALK'
Then all other stations connected to the node, present in
the USER list but idle, get the message
GxABC>> Hello fred, can I have a chat, type 'TALK'
displayed on their terminal.
Note that merely connecting to the node does not consitute
being connected to the switch. Stations connected to the
switch appear in the USER list.
3.14 SYSOP
The SYSOP command has been enhanced to increase the level of
security offered. One problem of the old system is that the
password is easily visible unless the user repeats the SYSOP
command a number of times. Even then, correlation between
passwords is easy, so the password needs frequent changing.
To reduce the change period, and make it harder to discover,
the node will accept a string of characters and scan it for
the password. Hence a response of, say, 30 or 40 characters
can be sent, with a random number of random characters
preceding the actual data and a random number following it.
This does not eliminate such attacks, but if used carefully,
it makes it quite a bit harder to attack.
3.15 LINKS
This command shows the current level 2 links to the node.
Displayed one per line, the two callsigns are shown followed
by the link state, port number and current retry count.
3.16 CALIBRATE
This command allows remote calibration checks of the
transmitter deviation. Its syntax is
CALIBRATE period [ toggle ]
The period ( 1 to 60 seconds ), is the time for which the
transmitter will key up for with constant tone. It is
undefined as to which tone will be sent. If the second
parameter is given, the node will toggle between the tones
every [toggle] seconds. The toggle must be between 1 and
[period] seconds. If a period is not given, the user is not
sysop or manager, or if it is out of range, the command is
ignored. If the tone generator is busy because it is about
to send a CWID sequence, a 'busy' message is returned. Note
- quite often it can appear that the node has locked up
having failed to transmit the full calibrate period. In
fact, this is usually the hardware PTT watchdog in the TNC.
The node thinks it is still sending but the hardware timer
has removed the PTT signal.
3.17 DXCLUSTER
The DXCLUSTER command operates just like the BBS command in
that it may be used to effect a connection to a DXcluster
(assuming there is one nearby). It should be disabled if it
is not intended to be used to access a cluster.
The syntax of the command is :
DXCLUSTER [ * | ? | callsign ]
With no parameter, the command connects to a station
previously specified by the use of the DXCLUSTER command
with a callsign as a second parameter. Setting the DXCLUSTER
to allow this may only be done by a sysop. The '*' option
may also only be executed by the sysop, this command clears
a previously specified DXCLUSTER.
The '?' option ( or any text if not sysop ), prints out the
current DXCLUSTER station setting.
If no DXCLUSTER is set, the command issues an error message
if it is invoked with no other parameters.
The idea of this command is that, like with the 'bbs'
command of the 'BPQ software, a user may connect to the
local DXCLUSTER from the node.
3.18 HELP
The HELP command gives a message from the ROM. In general,
it is expected that the message will be designed to assist
new users in understanding the operation or configuration of
the node. The message may span many lines, and may be
changed when the rom is programmed. As delivered, it
contains a brief help screen detailing the main ( user )
changes to the code.
3.19 CTEXT
The CTEXT command sets or displays a message sent to a user
who connects to the node by uplinking to the node's alias.
The syntax of the command is :
CTEXT [ message ]
With no parameter, the current message is displayed. If the
user is also a sysop, and if text follows the command, that
text becomes the new connect text. When a '*' is
encountered, the message is terminated ( it is also
terminated by a newline ). Hence, to clear the message, type
the command 'ctext *'.
A message is only sent if there is a ctext message set and
if the relevant bit is set in the mode command parameter as
described in section 3.5.11.
3.20 BTEXT
The BTEXT command sets or displays the additional beacon
text sent along with the beacon packets.
The syntax of the command is :
BTEXT [ message ]
With no parameter, the current message is displayed. If the
user is also a sysop, and if text follows the command, that
text becomes the new beacon text. When a '*' is encountered,
the message is terminated ( it is also terminated by a
newline ). Hence, to clear the message, type the command
'btext *'.
Normally, beacon packets are UI frames that contain the node
callsign and alias. If a beacon message is set, the text of
the message follows the alias in the same packet. It is
strongly suggested that beacon packets be kept brief !!!.
3.21 ACL
This is probably the most complex additonal command in the
program. It should be used with care, and only when you
really understand its operation - mistakes can result in the
need to go out to a remote site ( probably when it is cold
and wet ) to reconfigure the node.
The command allows selective control, based on callsign, of
a list of different events. The ACL contains two types of
entry, a default value and zero or more callsigns, each of
which are associated with a value. When one of the
controlled events occurs ( such as an incoming level 2
connection or a nodes broadcast ), the ACL is scanned for an
entry that matches the callsign of the sender. If a match is
found ( but see below ), the value associated with that
callsign is used to determine the action the node will take.
If no match is found, the default value is used.
Each bit of the value controls a different function, as
shown below :
BIT OPERATION
======================================================
0 bar incoming level 2 connection
1 bar outgoing level 2 connection ( downlink )
2 ignore nodes broadcasts from this station
3 bar gatewaying at level 3 to/from this station
4 bar incoming level 4 connections
5 bar outgoing level 4 connections
6 ignore SSID in matching an entry
So if for example an entry exists for a callsign G99XXX of
6, then the node will not allow outgoing level 2 connections
to the node ( downlinks ), and will ignore node broadcasts
from that station. Note that these commands only operate on
the events themselves - if G99XXX creates a level 2
connection, the node will quite happily use it itself.
The 'ignore ssid' bit is used to match a callsign without
regard to its SSID. This makes life interesting when finding
a match, so the list is scanned twice, once for an exact
match, and then for a match ignoring SSID if an exact match
is not found. There can only be one exact match, but when
searching for a match without using SSID, the first entry
found will be used.
The syntax of the command is as follows ( 3 versions )
ACL * value
ACL callsign + value
ACL callsign -
If you are not sysop, or if ACL is given on its own, the
current contents of the ACL are shown. The first form of the
command changes the default value, the second form makes an
entry in the list, the last form removes an entry from the
list. It complains about syntax errors.
A few moments thought will show that the sequence of
commands
connect to node
execute sysop or manager command
type the command ACL * 127
disconnect
is quite catastrophic. You will not be able to get back in
again apart from via the host port and noone will be able to
connect to or from the node. If you intend to experiment
with the command, you should start by entering your own
callsign with a value of zero to ensure that you can get
back in again !!!.
The list can be used as an 'accept' or 'reject' list by
judicious use of the default. To create a list that excludes
specific calls, put them into the list with the required
bits set in the value. The default should be zero. To create
an 'accept' list, put entries in with the required bits zero
and set the corresponding bits in the default. Individual
bits may be used to create accept or reject lists for each
function.
The command steals buffers at a rate of one buffer per four
entries in the ACL. Also, a long ACL will slow the node down
nicely - so think before you enter a long list.
This command is for experimental purposes - if you find any
bugs, let me know please ( I have not fully tested the
gateway bit for example ). Also, it is not intended for
malicious use but to allow fine control to be exercised over
backbone networks. If I get lots of negative responses back,
the command will go !
3.22 CLOSEDOWN
The closedown command is used to shut down the node
remotely. If successfully executed, the node will
effectively stop operating until it is reset ( eg by a power
up ). The node's configuration ( routes, messages etc ) are
not destroyed - the node simply hits a HALT instruction. You
must be sysop to execute the command.
The syntax of the command is:
CLOSEDOWN A
The node will respond with 5 numbers just as for when the
sysop or manager command was executed. Yes, you guessed, the
node expects another password. Give it correctly and the
node closes down completely. Get it wrong and you lose your
sysop status. This obtuse and awkward syntax is designed to
make sure it is not accidentally executed.
3.23 ALIAS
The ALIAS command allows the node's alias to be changed. The
syntax is :
ALIAS [ * | new-alias ]
If no parameter is given, or if the user is not SYSOP or
MANAGER, the current alias is displayed. If the alias is
deemed to be a valid alias, the node's alias is changed to
the new one entered. Note that the algorithm that checks for
the alias structure is a bit queer. It is however, the
original algorithm of TheNet and I am loth to change it for
fear of side effects. Note too that the companion CALLSIGN
command is NOT included - chaos is not something I crave. If
the sysop gives the parameter of '*', the node's alias is
cleared.
3.24 BBSALIAS HOSTALIAS DXCALIAS
These commands are used to enable the node to respond to up
to three additional aliases. The syntax of each is the same,
and by way of example the BBSALIAS syntax is :
BBSALIAS [ * | new-alias ]
If not sysop, if no new alias is specified, or if it does
not pass the weird alias syntax checker ( see 3.23 ) then
the current alias is displayed. If not, the alias is
changed. If '*' is given, the alias is cleared.
The aliases so entered are nothing to do with the node's
identity. If a BBS alias is set, for example to MXMBBS, then
the node will listen for level 2 connects to that alias. It
will respond to them and will automatically invoke the BBS
command. The use will also get the optional welcome (ctext)
message and 'trying to connect to ....' messages if enabled
by the appropriate 'mode' parameter.
The idea is that where a node sits on a channel that does
not have access to the local host, BBS or cluster, the
normal aliases of those stations may be enabled in the node
to allow consistent access to the local services. Note that
the three stations do not have to be a BBS, Host and
cluster, it could be three BBSes or any other combination.
3.25 IPSTATS
The IPstats command has the same basic syntax as the PARMS
and MODE commands. When invoked without parameters, it
displays the current stats. Each statistic may also be
altered by sysop.
In addition to the standard IP MIB, there is an additional
parameter used to set the level 2 default modes, and the
first entry in the MIB is used to enable or disable the
router.
The complete set of IP MIB stats are included for
compatibility with other IP systems, but several are not
used. Also, the stats are 16 bit counters not 32 bit
counters as in NOS. Like NOS however, the stats do not reset
every hour, they must be cleared by the sysop. They will
however wrap around at zero.
The entries are:
1 Port default modes
2 Enable / Disable the IP router fuctions
3 Default IP Time To Live
4 IP Received frames
5 IP Header Errors
6 IP Input Address Errors
7 IP Forwarded Datagrams
8 IP Unknown Protocols
9 IP input frames Discarded
10 IP Input frames Delivered
11 IP Output Requests
12 IP Output Discards
13 IP Output No Routes errors
14 IP Reassembly Timeout errors
15 IP Reassembly Required errors
16 IP Reassembly OKs
17 IP Reassembly Fails
18 IP Fragmentations completed OK
19 IP Fragmentation Failures
20 IP Fragmentation Creates
The default mode word may be set to 0, 1, 2 or 3. Each bit
controls a port, with bit 0 controlling port 0 ( radio port)
and bit 1 controlling port 1 ( RS232 port ). When set to 1,
the default mode for that port when sending on a level 2
connection will be Datagram. When set to 0 it will be by
Virtual Circuit. The default mode is used when no other
information is given, either by the ARP table or by the TOS
bits in the IP header.
The enable / disable word may be set to 0 or 1. When set to
0, the operation of the router is stopped, when set to 1 the
router functions.
The IP Time To Live ( TTL ) word is used to set the number
of routers through which an IP frame may pass before it is
discarded. It is similar to the node layer 3 TTL word. It
may be set to any value up to 255, but values below 2 make
no sense and are therefore not permitted.
The IP fragmentation reassembly timeout counter is not used
as the node is just a router. It is left set to 30 seconds
just to show which one it is !
The rest are just statistics. The patient user can have
hours of fun working out which ones are not used ( or just
think about it for a second or two ).
3.26 IPADDRESS & IPBROADCAST
These commands are used to set or display the IP addresses
used by the node. The syntax of each is (by way of example):
IPADDRESS [ ipaddress ]
where ipaddress is in the form
nnn.nnn.nnn.nnn
where nnn is an integer in the range 0..255
So to set the node IP broadcast address to that used over
here, the command would be :
IPBROADCAST 44.131.0.0
The IPADDRESS is the address that the node will respond to.
It is used only as detailed in section 7. The IP broadcast
address is the one used to denote broadcast packets that
will be largely ignored. Note that port addressing is NOT
currently supported. Anyone who finds this limiting, drop me
a line and I'll see if I can change it.
3.27 IPROUTE
This is one of the two main databases used by the node. The
IP Route table is used to tell the router where to send a
frame for a specific detination. It maps addresses or
address ranges to a gateway IP address and to sub-network
ports. The ARP database then tells the node what station
corresponds to that address and protocol. The node supports
two subnet protocols, AX25 and Netrom.
The database is stored in an ordered list, in decreasing
order of the number of relevant bits. This is to permit
searching of the database when trying to find a specific
destination. Given an address, it scans addresses with
decreasing numbers of bits until it finds a match. The
syntax of the command is as follows :
IPROUTE [address [ / bits ][ + port [gateway [metric]]]]
or
IPROUTE [address [ / bits ][ - ]]
In the first form, it makes an entry in the table, in the
second it deletes one. Only sysop or manager may effect such
a change. The parameters are as follows :
address The amprnet address in the form nnn.nnn.nnn.nnn
bits The number of significant bits (eg 44.131.0.0 / 16)
port The port, either 0 or 1 for AX25 or n for NETROM
gateway The optional gateway for this dest. nnn.nnn.nnn.nnn
metric Currently not used, a numeric value
When an entry is made with a specific number of bits, the
address is 'masked off' to that many bits, so enter an
address of 44.131.16.31 / 24 and it will get entered as
44.131.16.0. The valid range for the number of bits is 1 -
32.
3.28 ARP
The ARP table maps a pair of address+port to hardware
address+subnetwork mode. The address is either a destination
or a gateway in the form nnn.nnn.nnn.nnn. The protocol is
either netrom or ax25. The hardware_address is a callsign
and the subnetwork mode is DG or VC ( only has significance
for level 2 links ).
The syntax of the command is :
ARP [ destination [ + [ P ] protocol callsign [ mode ] ] ]
or
ARP [ destination [ - protocol ] ]
In the first form an entry is made in the table, in the
second an entry is deleted. This is only permitted for sysop
or manager.
The parameters are :
destination An address of the form nnn.nnn.nnn.nnn
P If present, marks the entry as 'published'
protocol AX25 or NETROM
callsign A valid amateur callsign, e.g. G8KBB-5
mode DG or VC
If 'P' is entered, then the node will publish the address.
Specifically, if an ARP request is seen by the node for a
station with the address given, it will send a response
advising the caller of the callsign to be used.
More details on the operation of the router are contained in
section 7.
3.29 UI
The UI command allows a string to be sent as a Level 2 UI
frame. The syntax is
UI dest string_of_text_ending_in_return
Dest is a callsign like destination such as 'MAIL'. What
will happen is that a single UI frame will be sent with a
source callsign of the user who entered the command,a
destination callsign of dest, and the rest of the string as
text.
It is designed to be used in situations where a local BBS
does not have access to a common channel and wishes to send
mail notification packets. Not surprisingly, the ability to
do this is BBS specific.
4. Other Changes
This section covers the other miscellaneous changes to the
software.
4.1 Command Processor
The command processor has been altered. In general, but not
in all cases, commands only appear on the 'help' menu when
they are enabled, so for example the 'BBS' command will not
be shown unless it has been enabled with the 'BBS +'
command. The exception is the sysop commands, like MODE,
LINKS and PARAM, which are never shown to users but are of
interest to them. If the appropriate bit is set however in
the MODE command ( see 3.5.11 ), then for the sysop or
manager, all commands appear in the help prompt - EVEN IF
DISABLED.
The help screen now shows commands in a combination of upper
and lower case characters.
4.2 Beacon digi
It is possible to set a digi in the address used for beacon
packets. Details of how to do this are contained in the
configuration guide. Note that this is provided for those
rare occasions when there is a genuine need. This is rarely
the case and should not be done unless really necessary.
5. CWID keyer.
The CWID keyer sends the station callsign in CW by
alternating between the two modem tones. This is nominally
sent at 20 wpm once every 30 minutes, but the speed and
period can be changed remotely.
After a delay of 30 minutes, the callsign is sent appended
to the end of the next data packet that is sent over the
air. There is a 500 ms delay after the end of the data
packet before the call is sent.
The program prefers to send CWIDs appended to ordinary data
packets. However, if one minute after the CWID has supposed
to be sent it is still pending because no data packets have
been sent, it will key up the transmitter anyway. Persist,
TxDelay and other parameters are honored, but the process
involves changing the SIO mode and this will have an
aggrevating effect on any packets being received in full
duplex mode.
6. Version X-2.
X-1 was the first release of this code. The objective is to
get some practical feedback and test the code before the
full release, version X-2, which I hope will be very similar
to this release ( X-1H ). I have been saying this for some
time now, but things keep getting added. The next version
will hopefully be a significant change with extensions from
G8AMD, but this may be some time off yet...
Version X-1A added the escape-N command and the change to
the connect, nodes and reset commands. The timers were also
added to the stats command.
Version X-1B removed all the escape commands apart from C,D
and P. It also added the MODE command and extended the + and
- command qualifiers to all commands.
Version X-1C added TALK, MANAGER and AUDIT. The SYSOP
command was enhanced and the INFO command was altered to
limit the length of a message ( a bug in the original
version of TheNet ). The help screen was changed to display
commands in a combination of upper and lower case.
Version X-1D extended the auditing and statistics to cover
auditing everything but level 3, and statistics of the CPU,
Level 1, Level 2 and timers.
Version X-1E added beacon timer control, the connect
redirector, the nodes dump facility, level 3 & 4 statistics
and the LINKS and CALIBRATE commands.
Version X-1F added the CLOSEDOWN, DXCLUSTER, ACL, CTEXT,
HELP and BTEXT commands. Another parameter was added to the
MODE command to control textual messages. The mod suggested
by DF2AU to correct the DCD latchup was included. Additional
statistics were added covering CRC errors, receiver overrun,
transmitter underrun and framing errors.
Version X-1G added mainly the IP router, with the following
commands to control it - IPROUTE, ARP, IPSTATS, IPADDRESS,
IPBROADCAST. In addition, the ALIAS, BBSALIAS, HOSTALIAS and
DXCALIAS commands crept in, as did QUIT as an alternative to
BYE. The help messages extended to enable nodes in the
routes list to appear as alias:callsign, and an extra byte
on the MODE command allowed '#' nodes to be selectively NOT
broadcast. The order of HELP and HOST commands changed so
that 'h' on its own gave help not host. The code was
optimised with some time critical parts being recoded in
assembler and a peephole optimiser being used for additonal
improvements.
Version X-1H fixed 3 bugs in X-1G.
If you read this and say 'Pah. it doesn't do XXXXX' or 'It
still doesn't do YYYYY' or anything of a similar nature,
don't keep it to yourself. Tell me. I may well do it. An
example of this is a concern raised about the way the nodes
broadcast works on a multi-tnc crosslink.
7. The IP router
The IP router co-exists in the node with the other software.
It is connected to the L2 and L3(netrom) protocol machines,
and is managed from the l7 switch. It will accept data from
L2 Datagrams, L2 Virtual Circuits or NOS protocol extended
netrom frames. It will output to these 3 depending on the
setting of the IProute and ARP tables.
The router supports the IP options of NOS and also does IP
fragmentation. Level 2 segmentation is not supported. In
addition, ICMP is implemented in so far as it is needed to
respond to errors or PINGs. No higher layer support is
provided, ie TCP is not implemented, ip_send() and
ip_receive() are only implemented in so far as they are
needed for ICMP. You can therefore PING it but anything else
will solicit an ICMP error message.
It will respond to ARP & REV_ARP requests but will never
initialte them. The MTU is 256 for AX.25 and 236 for netrom.
It will accept longer datagrams than this and fragment the
output but it is not recommended as it merely wastes RAM.
It is possible to be creative in the use of L2 datagram and
virtual circuits by use of the port default settings and the
ARP table. The algorithm used is :
When a frame is to be sent, the ARP table is scanned
for the appropriate entry. The entry tells it what
callsign to use. For netrom encapsulation, it is send
to the netrom protocol handler. For AX.25 encapsulation
the following applies. The ARP table may indicate DG or
VC. In this case, that mode is taken. If there is no DG
or VC entry, the TOS bits are examined. If the delay
bit is set, a datagram mode is selected. If not, and
the reliability bit is set a virtual circuit is
selected. If neither bit is set, the default mode for
that port is used to select a mode ( see IPstats
command, first parameter ).
Port addressing is not supported at the moment.
The IP router is manually controlled - no rspf or rip, or
even arp requests. This is because 32K of RAM does not allow
such niceities as queueing frames whilst waiting for address
resolution.
8. MISC
Anyone interested in a copy of the program, drop me a
message on GB7MXM.#36.GBR.EU Also, any suggestions for
change gratefully received.
Dave G8KBB
7, Rowanhayes Close
Ipswich
IP2 9SX
England
