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Bug #3357

osmo-bsc doesn't perform RSL MODE MODIFY on ASSIGNMENT if channel is compatible.

Added by laforge 3 months ago.

Status:
New
Priority:
Normal
Assignee:
sysmocom
Category:
-
Target version:
-
Start date:
06/26/2018
Due date:
% Done:

0%

Estimated time:
Spec Reference:

Description

As neels points out in https://gerrit.osmocom.org/#/c/osmo-bsc/+/9671/6/include/osmocom/bsc/lchan_fsm.h@53

The current master branch code does not ever perform a Chan Mode Modify, so neither does this refactored code. It is relatively trivial to add it, but I decided to not add more to this refactoring.

For example: we gave an MS a TCH/F lchan for initial Channel Request. Now a BSSMAP Assignment Command tells us to assign a TCH/F to the MS. We don't need to find a new unused lchan, we can just use the assigned one. All that's needed is to send a Chan Mode Modify to the BTS and go through the FSM states that set up the RTP stream. But we don't do that yet; so far, instead we look for a completely new lchan. (If the lchan mode already matches, we do use the current lchan. See assignment_fsm_start() in assignment_fsm.c )

We should start by creating a BSC_Tests.ttcn test case for this specific behavior. It would then fail until we fixed our BSC.

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