Hi,
I have a radio link between two systems.
The maximum packet size in this link is 254 bytes.
On both sides this limit is set:
root@travelmate:~# uname -r
4.2.0-1-amd64
root@travelmate:~# ifconfig ax0
ax0 Link encap:AMPR AX.25 HWaddr FH4GOU-1
UP BROADCAST RUNNING MTU:254 Metric:1
RX packets:245 errors:0 dropped:0 overruns:0 frame:0
TX packets:67 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:10
RX bytes:6492 (6.3 KiB) TX bytes:8810 (8.6 KiB)
root@travelmate:~# grep ax0 /etc/ax25/axports
ax0 FH4GOU-1 115200 254 1 AX25 over LoRa
root@tardis:/usr/src/sketches/mkiss# uname -r
4.1.18+
root@tardis:/usr/src/sketches/mkiss# ifconfig ax0
ax0 Link encap:AMPR AX.25 HWaddr TRDS01-1
UP BROADCAST RUNNING MTU:254 Metric:1
RX packets:569 errors:1 dropped:0 overruns:0 frame:0
TX packets:212 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:10
RX bytes:14033 (13.7 KiB) TX bytes:4987 (4.8 KiB)
root@tardis:/usr/src/sketches/mkiss# grep ax0 /etc/ax25/axports
ax0 TRDS01-1 9600 254 1 AX.25 over LoRa
Transmitting/receiving packets < 254 bytes works fine; e.g. IDENT with
not too large texts and also "axcall"-sessions with small pieces of
texts.
But if I invoke "mheard" which returns quite a bit of text,
communication fails. I checked with wireshark and I saw that even
though there's that 254 bytes MTU, I still get packets way larger:
nr time source target protocol length info
23 11.084320000 FH4GOU-01 TRDS01-01 AX.25-NoL3 271 Text
What can I do to prevent these overly large packets?
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