Sriram

Okay you have to tackle this problem by layers. reading what you have
wrote implies to me that a layer lower than that you see the trouble
with is causing the problem. (The OSI 7 layer model is something to look
at but you probably wont find any reference to amateur radio packet)

I'd suspect the radio link/freq/modulation depth etc.

Keep in mind that TCP/IP over radio is slow and if you are doing tests
you must allow for this. Dont fill up the outbound buffer with data!
TCP/IP for LANs is a lot faster than radio so the RTT discovery will put
a flood of packets onto the interface when you first start a connection.
This will only confuse the problem.

You tried doing a ping test and Bob N7XY suggested increasing the wait
time. Also increase the length of the packet (bytes) up to the interface
MTU. This will prove if the RF path is flakey. (signal strength,
modulation depth/deviation, same frequency etc) ie if you have a 1 in 40
bit error it is going to show up in far less packets of shorter length
than of longer ones. If the signal strength is good I'd be upset if I
was losing more than 5% of the packets. (This is why you use a much
shorter packet length on HF radio as there is more likelihood of a
packet error)

Get the above worked out with pings until you even look at anything TCP
(eg SSH/FTP)

I use to adjust the TXdelay and TXtail by running a continuous long
packet ping and changing them dynamically. When the errors starting
happening I would back it off one notch. You can also do the same thing
with setting deviation and adjusting freqeuency but it is better
starting with RF/radio tests with suitable test equipment first.

Cheers Bob VK2YQA


Sriram wrote:
Hi Bob,

Have you tried adjusting txdelay and possibly txtail (using kissparms)?


We tried varying the values. But it did not make significant
difference in the error rate or the ssh connection.

The default ping interval is one second. You may need to increase this
(ping -i 2).

Do ftp and smtp also have problems?


We tried telnet. Telenet is able to connect sometimes, not all the
time.


I haven't tried SSH over AX.25, but, but at one time it was pretty
clear that it was not permitted by Part 97, because it obscured the
meaning of a transmission. There were some extensive revisions to the
rules a few years ago and this may have changed.


Yes. SSH over AX.25 is allowed now.

Thanks,
Sriram


73, Bob N7XY