Opened 8 years ago

#15 new defect

Section 4.8: SSRC signaling

Reported by: bernard_aboba@… Owned by: draft-ietf-rtcweb-rtp-usage@…
Priority: major Milestone: milestone1
Component: rtp-usage Version: 1.0
Severity: Active WG Document Keywords:


4.8. Choice of RTP Synchronisation Source (SSRC)

Implementations are REQUIRED to support signalled RTP SSRC values,
using the "a=ssrc:" SDP attribute defined in Sections 4.1 and 5 of
[RFC5576], and MUST also support the "previous-ssrc" source attribute
defined in Section 6.2 of [RFC5576]. Other attributes defined in
[RFC5576] MAY be supported.

Use of the "a=ssrc:" attribute is OPTIONAL. Implementations MUST
support random SSRC assignment, and MUST support SSRC collision
detection and resolution, both according to [RFC3550].

[BA] I think you need to be more specific here. Does this mean that an implementation needs to be able to render an SSRC that isn't declared in an a=ssrc: attribute? Personally, I'd suggest that this is useful because WebRTC gateways may not know what SSRCs to expect so they can't signal them. Also, it enables operation in RTP topologies (like an RTP translator). However, keep in mind that implicit SSRCs aren't something the current WEBRTC API supports.

Also, if you're going to require support for a=ssrc: attributes, there will be other attributes that will come along with that.

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