[rtcweb] Question about srtp_mki in DTLS/SRTP

[Bernard Aboba <[e-mail]>]

A question about negotiation of the use of the SRTP MKI field in DTLS/SRTP.

RFC 5764 Section 4.1.3 has this to say about negotiation of support for the
SRTP MKI field in SRTP/SRTCP:

4.1.3 <https://tools.ietf.org/html/rfc5764#section-4.1.3>.  srtp_mki value

   The srtp_mki value MAY be used to indicate the capability and desire
   to use the SRTP Master Key Identifier (MKI) field in the SRTP and
   SRTCP packets.  The MKI field indicates to an SRTP receiver which key
   was used to protect the packet that contains that field.


Looking at draft-ietf-rtcweb-rtp-usage, draft-ietf-rtcweb-security and
draft-ietf-rtcweb-security-arch, there is no additional mention of the
SRTP MKI field.


What can be concluded about negotiation and support for the SRTP MKI
field within WebRTC implementations?


Do existing WebRTC implementations have the capability to receive or
send with the SRTP MKI field (e.g. if the peer implementation requests
it?)


Do existing WebRTC implementations indicate a desire to use the SRTP MKI field?


Does the IETF RTCWEB WG have any additional guidance to provide on
this topic beyond what is in RFC 5764 Section 4.1.3?