Bug #2701

RTCP SDES contains bogus information

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

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


Spec Reference:


When looking at the RTCP generated by osmo-bts, we see bogus content, such as "unknown@unknown" as CNAME and only the ORTP version as "TOOL" name.

Would be better to use libortp's rtp_session_set_source_description() API to put in some reasonable values. Of course RFC3550 didn't assume/expect GSM / cellular usage, so the recommendations for the content of CNAME, NAME, EMAIL, PHONE and TOOL sdes items are not entirely applicable.

I would suggest we use something that makes it easy to map the RTP stream to what it is used for. So on Abis, the BTS unit-id as well as the timeslot/sub-slot definitely should be encoded somehow to aid the mapping of RTP streams to physical GSM resources. The MSISDN is unfortunately not known to the BTS, so "PHONE" cannot reasonably be filled-in :(

Associated revisions

Revision d1dd22c3 (diff)
Added by laforge about 3 years ago

Add a new osmo_rtp_set_source_desc() function to set the RTCP SDES items

This allows the users of libosmotrau to set the content of the SDES
items to something more useful than their compile-time defaults.

Change-Id: Ice794f9e0c6caeea1c67520c12efbfa375d1fb82
Related: OS#2701

Revision be4a2088 (diff)
Added by laforge about 3 years ago

Put useful information in RTCP SDES.

The RTCP Sender Description is supposed to contain useful information
to identify the source of the RTP stream. So far, it only contained
compile-time default data of libortp. Let's put the BTS UnitID, the
lchan number and the OsmoBTS version in there.

This change requires libosmo-abis Change-Id Ice794f9e0c6caeea1c67520c12efbfa375d1fb82

Change-Id: Id6ce7188354d3a0517661c9648854ec829ef1cac
Related: OS#2701


#1 Updated by laforge about 3 years ago

  • Status changed from New to In Progress
  • Assignee set to laforge
  • % Done changed from 0 to 90

#2 Updated by laforge about 3 years ago

Internet Protocol Version 4, Src:, Dst:
User Datagram Protocol, Src Port: 10351, Dst Port: 3334
Real-time Transport Control Protocol (Sender Report)
Real-time Transport Control Protocol (Source description)
    [Stream setup by GSM A- (frame 15075)]
    10.. .... = Version: RFC 1889 Version (2)
    ..0. .... = Padding: False
    ...0 0001 = Source count: 1
    Packet type: Source description (202)
    Length: 20 (84 bytes)
    Chunk 1, SSRC/CSRC 0x318C8FD4
        Identifier: 0x318c8fd4 (831295444)
        SDES items
            Type: CNAME (user and domain) (1)
            Length: 13
            Text: bts@
            Type: NAME (common name) (2)
            Length: 23
            Text: (bts=0,trx=0,ts=2,ss=0)
            Type: LOC (geographic location) (5)
            Length: 8
            Text: 1234/0/0
            Type: TOOL (name/version of source app) (6)
            Length: 21
            Text: OsmoBTS-
            Type: END (0)

#3 Updated by laforge about 3 years ago

  • Status changed from In Progress to Resolved
  • % Done changed from 90 to 100

changes merged

#4 Updated by laforge about 3 years ago

  • Status changed from Resolved to Closed

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