Feature #1914

Implement Early Classmark sending

Added by laforge almost 2 years ago. Updated almost 2 years ago.

Target version:
Start date:
Due date:
% Done:


Spec Reference:


The feature is about implementing the sending of a Classmark change
message when "early classmark sending control(es_ind)" is allowed by the
BTS in the SI3 message.
I saw on the source code, the classmark change is already implemented
but sent only upon receive of a classmark inquiry message.

So what I want is an option (like in mobile.cfg) to allow the early
sending of a classmark change (I think this msg is sent after receiving
a L2 UA frame when there is a service request or paging request)

Why I need this :
When using osmocom-bb on specific commercial operator, the mobile
application just before calling goes into a loop of
AuthRequest/CipheringModeCommand like this :

Ciphering mode command - 1
Ciphering mode command - 2
Ciphering mode command - 15

Ciphering Mode Complete - 1
Ciphering Mode Complete - 2
Ciphering Mode Complete - 15

funct=UI - 1
funct=UI - 2
funct=UI - 30

So the call is rejected immediately. I'm pretty sure it's because of the
none sending of the early classmark change even if it's not mandatory.


#1 Updated by laforge almost 2 years ago

  • Status changed from New to In Progress
  • % Done changed from 0 to 20

Relevant spec reference: TS 04.08 Chapter Early classmark sending

Any multi-band MS actually is required to implement early CM sending, so OsmocomBB was in violation of that so far. I've pushed some untested code to the laforge/early-cm branch of osmocom-bb.

#2 Updated by laforge almost 2 years ago

there's also a (similarly untested) laforge/early-cm branch in openbsc.git, which allows to configure whether early classmark is permitted in the cell or not.

#3 Updated by laforge almost 2 years ago

  • Status changed from In Progress to Resolved
  • % Done changed from 20 to 100

Both OpenBSC side and OsmocomBB side tested and committed/submitted.

#4 Updated by laforge almost 2 years ago

  • Status changed from Resolved to Closed

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