Support for RRID

[aboba]

As noted in the following message, the RRID is necessary in order to support robustness (RTX/FEC) with simulcast:
https://www.ietf.org/mail-archive/web/mmusic/current/msg18035.html

How is the RRID set in an RtpSender/RtpReceiver?

[aboba]

The text suggests that for simulcast the RRID is mandatory-to-use, and that the RRID is set to the value of encodings[].rid. If we can assume that ORTC implementations support RRID according to the specification, there may not be a need to set the RRID in an RtpSender/RtpReceiver.

[aboba]

Currently the rtpunhandled event provides the RID, but not the RRID:

dictionary RTCRtpUnhandledEventInit : EventInit {
DOMString muxId;
DOMString rid;
payloadtype payloadType;
unsigned long ssrc;
};

What if an unhandled FEC/RTX packet containing the RRID was received?

[aboba]

This is a corner case unlikely to be encountered within existing or planned implementations.