Re: [rtcweb] JSEP-19: Impact of BYE on ssrc table (Appendix B)

[Magnus Westerlund <[e-mail]>]

Hi,

I have to agree with Cullen here. If one sends a RTCP BYE on an SSRC 
that is signalled, then one better do an signalling update with a new 
signalled SSRC before starting the RTP stream if one changes ones mind 
about it being ended.

Cheers

Magnus

Den 2017-03-17 kl. 03:30, skrev Cullen Jennings:
>
> Looking at the RTP specs ... it seems like it would not matter if an
> endpoint initially learned about a SSRC via RTP or SDP, either way it
> seems like the state for the SSRC should be mostly removed at the BYE.
> Thoughts on why we would handle them differently ?
>
> (If we do need to handle them differently, this looks like an OK approach )
>
>
>> On Mar 10, 2017, at 3:31 PM, Bernard Aboba <[e-mail]
>> <mailto:[e-mail]>> wrote:
>>
>> In the algorithm described in Appendix B, SSRCs that are entered into
>> the SSRC table due to signalling are not distinguished from those that
>> are "latched" into the table dynamically.
>>
>> The distinction is important because only "latched" SSRCs should be
>> removed due to receipt of a BYE (or a timeout).
>>
>> My suggestion of how to address this is to add a "D" flag to an SSRC
>> table entry, indicating that the entry was added dynamically.
>>
>> For example:
>>
>>       If the packet has a MID, and the packet's extended sequence number
>>       is greater than that of the last MID update, as discussed in
>>       [RFC7941], Section 4.2.6
>> <https://tools.ietf.org/html/rfc7941#section-4.2.6>, update the incoming SSRC mapping table
>>       to include an entry [with the "D" flag set] that maps the packet's
>>       SSRC to the "m=" line for that MID.
>>
>> Also:
>>
>>       If the packet's payload type is in the payload type table, update
>>       the the incoming SSRC mapping table to include an entry
>>       [with the "D" flag set] that maps the packet's SSRC to the "m="
>>       line for that payload type.  In addition, route the packet to the
>>       associated "m=" line and stop.
>>
>> Then when a BYE is received, check the "D" flag:
>>
>>       If the packet is of type BYE, it indicates that the RTP streams
>>       referenced in the packet are ending.  Therefore, for each SSRC
>>       indicated in the packet that is found in the incoming SSRC table,
>>       first deliver a copy of the packet to the "m=" line associated
>>       with that SSRC, but then [if the "D" flag is set] remove the
>>       entry for that SSRC from the incoming SSRC table.
>>
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>
>
>
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-- 

Magnus Westerlund

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