[vr000m]

All the listed protocols came after HTTP. RTSP, SIP borrowed heavily (albeit badly in retrospect) from HTTP.

I do not have all the historical context (early 90s), but for WebRTC, the idea was to not define any new protocol(s) or do a clean slate design. but rather to just agree on the flavors of the various protocols, and then to universally implement those. We already had SDP, RTSP, RTP, SAP, etc. And the idea was to cobble together the existing protocols into something everyone could agree on (the young companies, the old companies, etc)

We ended up defining variations to the flavors that we already had and for the most part everything turned out okay (maybe the SDP plan wars did not end up where we wanted it, but… it was a good enough compromise).

For realtime media, if we are able combine “locator:identifier” issue, we will be able to make media and signaling work inband.

[Karrot_Kream]

I know they came later, so I'm still confused why RTSP and SIP weren't implemented atop HTTP. I realize that RTSP and SIP can push server to client, but there's ways around that, though perhaps long polling and Websockets weren't conceivable when RTSP and SIP were invented. I mean, in a pinch, I have an HTTP server serving a folder where SDP files are generated, and I've written clients that just look for a well-known SDP file and use that to consume an RDP stream. It's a ghetto form of "signaling" that I love using when doing experiments (not suitable for production for various reasons obvious to you I imagine.)

I'm not saying WebRTC had poor design decisions or anything. I think it was very smart for WebRTC to reuse SDP, RDP, etc so the same libraries and pipelines could keep working with minimal changes. It also means very little new learning for folks familiar with the rest of the stack.

> For realtime media, if we are able combine “locator:identifier” issue, we will be able to make media and signaling work inband.

+1000. I think RTSP+TCP is a decent way to do in-band signaling and media, and RTMP defines strict ways to send both anyway.

[numpad0]

To me, the whole typical IP Multimedia stack screams telco. They prefer to remove and reattach headers upon passing interfaces, separate control and data plane, and rely on synchronization for session integrity. Great when there's a phone line to HQ and a heavily metered satellite link to do a live, I guess...