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Feature #3236

Rx Assignment Failure from BSC does nothing

Added by neels 6 months ago. Updated 24 days ago.

Status:
New
Priority:
High
Assignee:
Category:
-
Target version:
-
Start date:
05/04/2018
Due date:
% Done:

0%

Resolution:

Description

The code actually says:

/* Receive an ASSIGNMENT FAILURE from BSC */
void msc_assign_fail(struct gsm_subscriber_connection *conn,
                     uint8_t cause, uint8_t *rr_cause)
{
        LOGP(DRR, LOGL_DEBUG, "MSC assign failure (do nothing).\n");
}

Thus, when the BSC encounters any failure of allocating an lchan and the MSC is told so, osmo-msc still waits it out, which is ridiculous.
(After a considerable timeout, the call fails, so classifying this as a Feature request, not a bug report.)
osmo-msc should instead abort any ongoing call setup and tell both sides that it's over right away.

I noticed this while dyn TS allocation in osmo-bts is buggy: paging and call alerting happily continues despite the first Assignment actually failing.

The way to reproduce exactly what I saw:

  • revert patch Ic06c8f0fe82ae8a06afa5defd93a685010687965 in osmo-bts
  • configure all as TCH/F_TCH/H_PDCH
  • place a voice call and run into chan activ nack

or otherwise cause a chan activ nack to result when trying to allocate a TCH/x for the call from the BTS,
which then propagates as an Assignment Failure towards the MSC (at least since osmo-bsc patch Ib204b4a5272f9b7b60ca5f932cd8a4c857316270)

(at time of writing those patches aren't actually merged yet, but from a future perspective I expect they will be.)

History

#1 Updated by neels 6 months ago

  • Description updated (diff)

#2 Updated by laforge 4 months ago

  • Assignee set to stsp

#3 Updated by laforge 24 days ago

  • Priority changed from Normal to High

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