Summary of 3GPP Change Request S4-260257

Document Information

• Source: InterDigital Pennsylvania
• Title: WebTransport protocol for real-time communication
• Specification: 3GPP TR 26.836 v0.0.1
• Study: FS_Q4RTC_MED (Study on QUIC-based media delivery for real-time communication and services)

Purpose

This CR documents the WebTransport media delivery protocol, including its features, benefits, and limitations for use in real-time communication services within the ongoing study on QUIC-based media delivery protocols.

Technical Contributions

Reference Updates

The CR adds six new normative/informative references related to WebTransport:
- IETF draft-ietf-webtrans-overview (WebTransport Protocol Framework)
- IETF draft-ietf-webtrans-http3 (WebTransport over HTTP/3)
- IETF draft-ietf-webtrans-http2 (WebTransport over HTTP/2)
- WebTransport API (MDN documentation)
- W3C Working Draft for WebTransport
- IETF WebTransport Working Group Charter

New Technical Clause: WebTransport (4.2.X)

Introduction (4.2.X.1)

• WebTransport is a framework enabling web clients (browsers) to communicate with servers over secure, multiplexed transport
• Positioned between WebSocket (limited to single ordered reliable TCP stream) and WebRTC DataChannel (P2P-oriented)
• Runs over HTTP/3 at high level
• Dual nature: both transport protocol (IETF) and Web API (W3C)
• Protocol stack includes HTTP3Transport mapping layer for feature negotiation, Extended CONNECT initiation, and datagram/stream mapping
• W3C API published as working draft; IETF standardization expected in 2026

Features (4.2.X.2)

• Session-based communication model under Web security model
• Supports multiple independent bidirectional and unidirectional streams
• Supports datagrams (unreliable, message-oriented delivery)
• All traffic multiplexed within same connection over HTTP/3
• Safely exposed to browser applications
• Dual specification: protocol level (IETF) and API level (W3C)
• HTTP/2 mapping available for environments without UDP/QUIC support

Benefits (4.2.X.3)

• Application-level abstraction: Web-compatible framework and API beyond raw QUIC transport
• Mixed traffic support: Combines reliable and low-latency traffic in single logical connection
• Web security integration: Origin-based access control, secure contexts, safe for untrusted applications
• HTTP integration: Mappings over HTTP/3 and HTTP/2 enable operation where UDP/QUIC unavailable
• Modern browser API: W3C API provides high-level JavaScript interface aligned with Web Streams paradigm
• Alternative to WebSockets: Native multiplexing and unreliable datagram support

Limitations (4.2.X.4)

• Client-server only: Primarily for client-server interactions; no standardized NAT traversal like WebRTC
• Security constraints: Limited to secure contexts (HTTPS); intentionally restricted low-level transport control
• Maturity concerns: W3C API still Working Draft; variable browser support
• HTTP/2 mapping differences: HTTP/2 fallback provides "many capabilities" but not identical transport properties to HTTP/3 version

Current Applications (4.2.X.5)

• Client implementations: Google Chrome and Microsoft Edge browsers support W3C WebTransport API over QUIC
• Server implementations:
• quiche (Rust): https://github.com/cloudflare/quiche
• aioquic (Python): https://github.com/aiortc/aioquic (experimental support)

Overall Assessment

This CR provides comprehensive documentation of WebTransport as a candidate protocol for QUIC-based real-time communication services, covering its technical characteristics, advantages for web-based RTC applications, deployment constraints, and current implementation status.