man listen

man listen

[Phil Maley]

Hi all

I'll get this message in while the list seems to be working...

I am trying to improve the performance of my ax25 system and one of
the few debugging tools is "listen". Unfortunately "man listen" only
provides a bare outline of the command line options and I can't find a
detailed description of how to interpret the output. For example, the
following output from "listen -ar" contains a "^" after the "UI". What
does that indicate?
uhf: fm VK6DLX-9 to APRS via VK6BBS-10 ctl UI^ pid=F0(Text) len 88

In this line, what does the "+" at the end of the line indicate?
axip: fm WA7V-2 to VK6DLX-7 ctl RR0+

In this line I guess the I17 means it is an information fram with
sequence ID of 17. What does the "+" after the 17 indicate?
uhf: fm VK6BBS to VK6AD ctl I17+ pid=F0(Text) len 5

According to the ax25 specification, modulo 8 sequence numbers should
be 0 to 7. Since I am seeing a sequence number of 74 here I assume
this link has negotiated modulo 128 operation.
uhf: fm VK6BBS to VK6AD ctl I74+ pid=F0(Text) len 250

A moment later however, on a fresh connection, I saw the sequence
number count up to 63 and cycle back to 0.

Here are some reject commands:
uhf: fm VK6AD to VK6BBS ctl REJ2-
uhf: fm VK6AD to VK6BBS ctl REJ0-
They don't seem to specify what frames have been rejected. The first
reject was sent after sequence number 24 arrived from VK6BBS. And what
does the "-" indicate?

In summary, does anyone know if there is a comprehensive write-up of
the "listen" command?

Thanks for reading this, and best 73
Phil Maley VK6AD

RE: man listen

[Riley Williams]

Hi Phil.

 > I am trying to improve the performance of my ax25 system and
 > one of the few debugging tools is "listen". Unfortunately,
 > "man listen" only provides a bare outline of the command line
 > options and I can't find a detailed description of how to
 > interpret the output.

I'm no expert on the listen command, but I do know the basic
AX.25 protocol, and I'm offering reasonable guesses as to what
each means. I could easily be wrong about some aspects of it,
so don't treat this as gospel.

 > For example, the following output from "listen -ar" contains
 > a "^" after the "UI". What does that indicate?
 >
 > uhf: fm VK6DLX-9 to APRS via VK6BBS-10 ctl UI^ pid=F0(Text)
 >		len 88

Presumably that the P/F bit was set. I read that line as "From
VK6DLX-9 digipeat via VK6BBS-10 to APRS, frame UI with POLL set,
Protocol ID F) (straight text), length 88 bytes".

 > In this line, what does the "+" at the end of the line
 > indicate?
 >
 > axip: fm WA7V-2 to VK6DLX-7 ctl RR0+

Presumably also that the P/F bit was set, but this is a response
frame. I read that line as "From WA7V-2 to VK6DLX-7 Receiver
Ready acknowledging all outstanding frames up to and including
frame 0".

 > In this line I guess the I17 means it is an information frame
 > with sequence ID of 17. What does the "+" after the 17
 > indicate?
 >
 > uhf: fm VK6BBS to VK6AD ctl I17+ pid=F0(Text) len 5

I read that as "From VK6BBS to VK6AD information of length 5
bytes using Protocol ID F0 (Straight Text), frame number 1 with
the POLL bit set, acknowledging receipt of all outstanding
frames up to and including frame 7".

 > According to the ax25 specification, modulo 8 sequence
 > numbers should be 0 to 7. Since I am seeing a sequence number
 > of 74 here I assume this link has negotiated modulo 128
 > operation.
 >
 > uhf: fm VK6BBS to VK6AD ctl I74+ pid=F0(Text) len 250

I read that as "From VK6BBS to VK6AD information of length 250
bytes using protocol ID F0 (straight text), frame number 7 with
the POLL bit set, acknowledging receipt of all outstanding
frames up to and including frame 4".

 > A moment later however, on a fresh connection, I saw the
 > sequence number count up to 63 and cycle back to 0.

Remember that I-frames have TWO sequence numbers, one for the
frame itself, the second for frames acknowledged as received.
You appear to be confusing them.

 > Here are some reject commands:
 >
 > uhf: fm VK6AD to VK6BBS ctl REJ2-

Read as "From VK6AD to VK6BBS acknowledging reception of all 
outstanding frames up to and including frame 1, and requesting
retransmission of frame 2 onwards, with the FINAL bit NOT set".

 > uhf: fm VK6AD to VK6BBS ctl REJ0-

Read as "From VK6AD to VK6BBS acknowledging reception of all
outstanding frames up to and including frame 7, and requesting
retransmission of frame 0 onwards, with the FINAL bit NOT set".

 > They don't seem to specify what frames have been rejected.
 > The first reject was sent after sequence number 24 arrived
 > from VK6BBS. And what does the "-" indicate?

See above analysis of each one.

 > In summary, does anyone know if there is a comprehensive
 > write-up of the "listen" command?

That I can't help you with, but hopefully the above will give
some clues.

Best wishes from Riley.
---
 * Nothing as pretty as a smile, nothing as ugly as a frown.

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.493 / Virus Database: 292 - Release Date: 25-Jun-2003

RE: man listen

[Phil Maley]

Hi Riley

Many thanks. It makes a lot more sense now.

73
Phil vk6ad

Re: man listen

[Tomi Manninen]

Hi,

Riley gave you a good explanation on the other issues. However a
quick note about modulo-128.

> According to the ax25 specification, modulo 8 sequence numbers should
> be 0 to 7. Since I am seeing a sequence number of 74 here I assume
> this link has negotiated modulo 128 operation.
> uhf: fm VK6BBS to VK6AD ctl I74+ pid=F0(Text) len 250

You can tell modulo-128 frames (connections) from regular by the
"EAX25" text at the start of the line. Like this:

  1: EAX25: fm OH2BNS to OH2RBI-1 ctl SABME+ 16:51:43

Also note that for EAX25 the sequence number display is pretty much 
broken in listen. As the numbers are simply concatenated you can not
tell which belongs to which...

In my opinion the old xNOS style AX.25 dump was much more readable
_and_ consistent with the other protocol dumps in listen. But that's
just me...

-- 
Tomi Manninen           Internet:  oh2bns@sral.fi
OH2BNS                  AX.25:     oh2bns@oh2rbi.fin.eu
KP20ME04                Amprnet:   oh2bns@oh2rbi.ampr.org

Re: man listen

[Rodolfo Brasnarof]

---
On 29 Jun 2003 at 17:04, Tomi Manninen wrote:


> In my opinion the old xNOS style AX.25 dump was much more
> readable _and_ consistent with the other protocol dumps in
> listen. But that's just me...


Fortunately, listen is opensource, and can be modified. I 
changed it a little to make it display the timestamp at the 
begining of the line, instead of the end. I made no other 
changes, but of course it's possible.

Re: man listen

[Tomi Manninen]

On Mon, 2003-06-30 at 20:59, Rodolfo Brasnarof wrote:
> ---
> On 29 Jun 2003 at 17:04, Tomi Manninen wrote:
> 
> > In my opinion the old xNOS style AX.25 dump was much more
> > readable _and_ consistent with the other protocol dumps in
> > listen. But that's just me...
> 
> Fortunately, listen is opensource, and can be modified. I 
> changed it a little to make it display the timestamp at the 
> begining of the line, instead of the end. I made no other 
> changes, but of course it's possible.

Yeah. I made a patch that brings back the NOS style dump as
command line option long time ago. I just never bothered to
send it to Craig. So you're right, I shouldn't complain...

-- 
Tomi Manninen           Internet:  oh2bns@sral.fi
OH2BNS                  AX.25:     oh2bns@oh2rbi.fin.eu
KP20ME04                Amprnet:   oh2bns@oh2rbi.ampr.org