[OpenAFS] Networking AFS related problem

Harald Barth haba@kth.se
Wed, 02 Feb 2022 09:10:43 +0100 (CET)

> Since AFS is working perfectly as soon as I change my WiFi connection
> to other connections, and the cell is perfectly reachable via a remote
> machine, I think the problem is with my ISP, but I don't have enough
> knowledge about AFS or networking to pinpoint the problem precisely.
> (Of course, "normal" web browsing is perfectly okay even with this
> problematic connection.)

Whem this occurs, then I am always reminded that AFS uses UDP over
it's own ports and not TCP with http or https.

> I would be very grateful if anyone can help me gather some more
> debugging info about this problem so I can give it to my ISP for them
> to fix it.

I would start with wireshark and filter on UDP ports 7000 and 7001,
then look if the packets are going out and if you get answers back
from the file servers and if you do if they are complete. Sometimes
bad networks drop or truncate UDP packets (either in or out) and if
they only truncate them, it can help to make your MTU size smaller, so
that not all default 1500 bytes are used. I test like 1400, 1200, ..
Restart afsd with additional parameter -rxmaxmtu SIZE.

Good luck,