WebRTC 的传输协议

WebRTC 的实现中媒体数据和媒体控制数据通过 RTP/RTCP 来传，媒体数据的处理及媒体数据传输控制基于 RTP/RTCP 来实现。除了 RTP/RTCP 外，连接建立，参数协商，RTP/RTCP 包的传输等过程由信令协议、peer connection 和 p2p 完成，这部分也用到了非常多的协议，包括 ICE，STUN，TURN，SDP，DTLS 等，这些协议有许多的 RFC 定义。这些协议大多也都随着时间在更新优化。

这里梳理一下相关的协议及它们的变化发展。

ICE 相关协议

RFC 5245, Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocols
RFC 6336, IANA Registry for Interactive Connectivity Establishment (ICE) Options
RFC 8445, Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal
RFC 8839, Session Description Protocol (SDP) Offer/Answer Procedures for Interactive Connectivity Establishment (ICE)
RFC 8838, Trickle ICE: Incremental Provisioning of Candidates for the Interactive Connectivity Establishment (ICE) Protocol
RFC 8863, Interactive Connectivity Establishment Patiently Awaiting Connectivity (ICE PAC)

ICE Protocol

STUN 和 TURN 相关协议

RFC 5389, Session Traversal Utilities for NAT (STUN)
RFC 7350, Datagram Transport Layer Security (DTLS) as Transport for Session Traversal Utilities for NAT (STUN)
RFC 8553, DNS AttrLeaf Changes: Fixing Specifications That Use Underscored Node Names
RFC 5928, Traversal Using Relays around NAT (TURN) Resolution Mechanism
RFC 8489, Session Traversal Utilities for NAT (STUN)

STUN Protocol

RFC 5766, Traversal Using Relays around NAT (TURN): Relay Extensions to Session Traversal Utilities for NAT (STUN)
RFC 6156, Traversal Using Relays around NAT (TURN) Extension for IPv6
RFC 8656, Traversal Using Relays around NAT (TURN): Relay Extensions to Session Traversal Utilities for NAT (STUN)

TURN Protocol

DTLS 相关协议

RFC 4347, Datagram Transport Layer Security
RFC 5746, Transport Layer Security (TLS) Renegotiation Indication Extension
RFC 7507, TLS Fallback Signaling Cipher Suite Value (SCSV) for Preventing Protocol Downgrade Attacks
RFC 6347, Datagram Transport Layer Security Version 1.2

DTLS Protocol

RFC 5763, Framework for Establishing a Secure Real-time Transport Protocol (SRTP) Security Context Using Datagram Transport Layer Security (DTLS)
RFC 8842, Session Description Protocol (SDP) Offer/Answer Considerations for Datagram Transport Layer Security (DTLS) and Transport Layer Security (TLS)

DTLS Protocol 2

SDP 相关协议

RFC 4566, SDP: Session Description Protocol
RFC 8866, SDP: Session Description Protocol

SDP Protocol