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Bug #4111

BSSGP SUSPEND ACK with unknown BVCI=0

Added by fixeria 5 months ago. Updated about 1 month ago.

Status:
Resolved
Priority:
Normal
Assignee:
Target version:
-
Start date:
07/17/2019
Due date:
% Done:

100%

Spec Reference:

Description

When a GPRS-attached MS initiates a circuit-switched service (e.g. SS/USSD or SMS), OsmoSGSN logs the following:

DBSSGP NOTICE gprs_bssgp.c:556 BSSGP BVCI=0 Rx BVC STATUS, cause=Unknown BVCI
DBSSGP ERROR gprs_bssgp.c:563 BSSGP BVCI=0 Rx STATUS cause=Unknown BVCI missing conditional BVCI IE

As far as I understand, OsmoPCU sends BSSGP SUSPEND (BVCI=0) to OsmoSGSN, and gets BSSGP SUSPEND ACK (BVCI=0) from it. So then OsmoPCU realizes that BVCI=0 is now known for some reason, and sends BSSGP STATUS (BVCI=0) with cause "BVCI unknown (5)".

Please see an attached capture. OsmoSGSN is bound to 127.0.0.10:23000, OsmoPCU is at 127.0.0.1:23000.

bssgp_suspend.pcapng.gz bssgp_suspend.pcapng.gz 3.18 KB fixeria, 07/17/2019 01:03 PM

Related issues

Related to OsmoPCU - Bug #2384: NSVCI=0 seems to cause problemsNew07/20/2017

Related to OsmoSGSN - Bug #4245: osmo-sgsn hitting assert during osmo-gsm-tester ping.py testResolved10/31/2019

History

#1 Updated by fixeria 5 months ago

  • Project changed from Cellular Network Infrastructure to OsmoPCU
  • Subject changed from GPRS Suspension Request with unknown BVCI to BSSGP SUSPEND ACK with unknown BVCI=0

#2 Updated by laforge 5 months ago

BVCI=0 is the signaling BVCI, which always exists. This is different from the p-t-p
BVCIs which are explicitly brought up by UNBLOCK procedures and the like.

So claiming that BVCI=0 is unknown is wrong in any case. It is perpetual.

#3 Updated by fixeria about 1 month ago

  • Status changed from New to Feedback
  • Assignee set to fixeria
  • % Done changed from 0 to 90

Please see:

https://gerrit.osmocom.org/c/osmo-pcu/+/16006 BSSGP: do not reject SUSPEND ACK / NACK messages
https://gerrit.osmocom.org/c/osmo-pcu/+/16007 BSSGP: properly print BVCI for signalling messages (BVCI=0)

#4 Updated by fixeria about 1 month ago

  • Related to Bug #2384: NSVCI=0 seems to cause problems added

#5 Updated by fixeria about 1 month ago

  • Status changed from Feedback to Resolved
  • % Done changed from 90 to 100

Merged.

#6 Updated by pespin about 1 month ago

  • Related to Bug #4245: osmo-sgsn hitting assert during osmo-gsm-tester ping.py test added

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