# What is SDP (Session Description Protocol)?

> SDP (Session Description Protocol, RFC 8866) is the text format that describes a media session — which codecs, IP addresses, ports, and parameters each side will use. It is not a transport itself; it rides inside SIP (or WebRTC) as an offer/answer exchange, so the two endpoints agree on how to send RTP before the media flows. Codec negotiation and NAT candidate exchange both happen in SDP. See /answers/what-is-sip, /answers/what-is-voice-codec, and /answers/what-is-webrtc.

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- Last reviewed: 2026-07-22
- Publisher: BroadNet (https://www.broadnet.me)

## Related

- [All answers](https://www.broadnet.me/answers)
- [Glossary](https://www.broadnet.me/answers)
- [What is SIP (Session Initiation Protocol)?](https://www.broadnet.me/answers/what-is-sip)
- [What are voice codecs (G.711, Opus)?](https://www.broadnet.me/answers/what-is-voice-codec)
- [What is WebRTC?](https://www.broadnet.me/answers/what-is-webrtc)
- [What is RTP (Real-time Transport Protocol)?](https://www.broadnet.me/answers/what-is-rtp)
- [Voice](https://www.broadnet.me/products/voice)