PCU <---> SGSN protocol trace

[Sipos Csaba]

Just to put an answer to this, the solution is to right click on the "data" part inside the UDP packet, and select "Decode as" and choose protocol "GPRS-NS", then click OK.

I also used filtering to limit the messaging to the PCU <--> SGSN part:

udp.srcport==23000 or udp.dstport==23000

Hope this will help others too.

Regards,
Csaba

----- Eredeti üzenet -----
Feladó: "Sipos Csaba" <sipos.csaba at kvk.uni-obuda.hu>
Címzett: "OpenBSC Mailing List" <openbsc at lists.osmocom.org>
Elküldött üzenetek: Szombat, 2015. December 5. 15:09:20
Tárgy: PCU <---> SGSN protocol trace

Dear list,

I just appear to have a strange UE behavior where the UE tries to Attach (both CS and PS), the Osmo-SGSN sends an Attach accept, but the UE never responds with an Attach complete, instead after 10 seconds it tries to re-attach.

I had an issue quite similar like this earlies where the UE requests for some IEs or the SGSN sends soething the UE don't like.

The point is, I would like to do protocol trace between the SGSN and the PCU, and I managed to see the traffic with Wireshark, but it was not able to dissect/recognise the protocols over the UDP layer.

Can someone please help me how to configure Wireshark to be able to dissect the involved protocols?

Thanks!

Csaba