RE: Issue 180: RTCP packet routing

Jiannan said:

“Some RTCP packet types need to be routed to more than one object and not all packet types will necessarily have SSRCs that allow the packets to be routed as described”.

[BA]  Digging into this some more, I believe you are correct.

Packets such as SDES and BYE may affect multiple objects (e.g. they affect aspects of RTP operation such as synchronization and conflict detection as well as the membership which in turn influences the RTCP reporting interval).

Also, looking at the list of Assigned RTCP packet types and formats, the situation with respect to SSRCs is somewhat more complicated than Section 8.2.3 assumed:
http://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml#rtp-parameters-4


For example, packet type 195, Extended inter-arrival jitter report (IJ) defined in RFC 5450 does not include SSRCs.

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   hdr |V=2|P|    RC   |   PT=IJ=195   |             length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      inter-arrival jitter                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       .                                                               .
       .                                                               .
       .                                                               .
       |                      inter-arrival jitter                     |
                +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Also, XR (defined in RFC 3611) includes an “SSRC of sender” field but the report blocks are defined separately:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |V=2|P|reserved |   PT=XR=207   |             length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              SSRC                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                         report blocks                         :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Since we cannot necessarily predict what XR metrics might end up in the Statistics API, we probably cannot make assumptions about the information within the report blocks.