Subject: [rtcweb] SRTP and draft-alvestrand-rtcweb-gateways

From: 🔓Dan Wing <[email-masked]>
Date: Fri, 5 Dec 2014 09:03:50 -0800

Today's adoption call for draft-alvestrand-rtcweb-gateways made me go read it again.  In its section titled "WebRTC device requirements that can be relaxed", it says this:

>    If a gateway serves as a media relay into another RTP domain, it MAY
>    choose to support only features available in that network.  This
>    means that it MAY not (need to) support Bundle and any of the RTP/
>    RTCP extensions related to it, RTCP-Mux, or Trickle Ice. However, the
>    gateway MUST support DTLS-SRTP, since this is required for
>    interworking with WebRTC endpoints.

That last sentence (starting with "However") is a requirement that cannot be relaxed which makes it out of place in a section titled "requirements that can be relaxed".  I agree with what it is saying, but either provide a full list of WebRTC device requirements that cannot be relaxed (in its own section), or go into more detail about how DTLS-SRTP needs to be implemented in a gateway.  As one example, a gateway between WebRTC and an RTP-only network (e.g., call center or whatever) or to a TDM PBX, will need to support DTLS-SRTP towards WebRTC, but will not support DTLS-SRTP (or any other sort of keying) towards the RTP-only network or TDM PBX.  Easiest is to simply remove the sentence starting with "However".  Also, a gateway should be able to function into a TDM domain (not just "an RTP domain").

-d