Bug #2384: NSVCI=0 seems to cause problems - OsmoPCU - Open Source Mobile Communications

Bug #2384

NSVCI=0 seems to cause problems

Added by laforge over 3 years ago. Updated over 3 years ago.

Status:

New

Priority:

Low

Assignee:

laforge

Target version:

Start date:

07/20/2017

Due date:

% Done:

Spec Reference:

Description

If I configure NSVCI=0 in omso-bsc.cfg for a given BTS, OsmoPCU will behave eratically in terms of the NS protocol layer towards the SGSN.

Basically, OsmoPCU will at some point decide the NS-VC is no longer alive and refuse NS_ALIVE messages from the SGSN with "NS_STATUS, Cause: PDU not compatible with protocol state"

Related issues

History

#1 Updated by laforge over 3 years ago

the problem is not 100% reproducible. In som cases, OsmoPCU will send FLOW-CONTROL PDUs every second, in which time the NS-VC stays alive. Only if there are no NS-PDUs exchanged for 60 seconds, OsmoPCU will start rejecting the NS_ALIVE PDU.

So something must be inhibiting the generation of NS_ALIVE in PCU-SGSN direction, as well as inhibiting the FLOW-CONTROL.

Interestingly, "show ns" on the PCU will show

Osmo-PCU# show ns  
Encapsulation NS-UDP-IP     Local IP: 0.0.0.0, UDP Port: 21000
Encapsulation NS-FR-GRE-IP  Local IP: 0.0.0.0
NSEI    96, NS-VC     0, Remote: SGSN, ALIVE UNBLOCKED, UDP         172.31.0.1:23000

#2 Updated by laforge over 3 years ago

Priority changed from Normal to Low

this might have been a "false flag" as two SGSNs were sending UDP packets to the PCU simultaneously. This in turn makes me wonder why we would accept UDP packts from a source address that doesn't equal the IP/port specified in the NSVC configuration.