Discuss why this can't be a RTP Header Extension

[kyzer-davis]

Some text, maybe in appendix.

the short; if we want compatibility with a=cryptex there is a chicken or egg scenario where the RTP header extensions would be encrypted rendering the conveyed SRTP context information to decrypt the packet data useless.

[valvo27]

extmaps are a thing now within the SDP that could add RTP Header Extensions. They are used in Webex App, but not widely used yet. I rather go the SDP route that we are currently in.