Session Description Protocol
SDP is the handshake language between any two endpoints setting up a call. WebRTC, SIP, and RTSP all use it. You can't debug codec mismatches, ICE failures, or video call setup without reading SDP.
What It Defines
SDP describes multimedia sessions for negotiation. An SDP offer/answer exchange (carried in SIP INVITE bodies or JSEP in WebRTC) negotiates codecs, payload types, ICE candidates, transport addresses, and DTLS fingerprints. Defines the v=, o=, c=, m=, a= line structure and the offer/answer model (RFC 3264).
Canonical (Normative)
Convenient (Practical)
Related References
The canonical publication point for finalized RFCs. If a protocol is standardized as an RFC, the RFC Editor text is the normative final reference. Published by the IETF, IRTF, IAB, and independent stream.
Related Specs
SIP is the PSTN of the internet. Every VoIP platform (Twilio, Vonage, AWS Chime, Asterisk, FreeSWITCH) speaks SIP. Building any communications product requires understanding INVITE flows, registration, and codec negotiation via SDP.
RTP carries all real-time media: VoIP, WebRTC, live video, and video conferencing. Understanding SSRC demultiplexing, jitter buffers, and RTCP feedback loops is essential for any media application.
Video calls (Meet, Zoom web), voice calls, peer-to-peer file transfer, and collaborative tools. The browser API surface for real-time A/V communication.