Internet-Draft Multiplexing RoQ and QDC October 2023
Engelbart & Ott Expires 25 April 2024 [Page]
Network Working Group
Intended Status:
Standards Track
M. Engelbart
Technical University Munich
J. Ott
Technical University Munich

Multiplexing RTP and Data Channels over QUIC


This document defines a multiplexing scheme for using RTP over QUIC and QUIC Data Channels in a single QUIC connection.

Discussion Venues

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Table of Contents

1. Introduction

One of the requirements in the development of RTP over QUIC (RoQ) ([I-D.draft-ietf-avtcore-rtp-over-quic]) was the ability to share a QUIC connection for RTP, RTCP, and other protocols. RoQ uses a flow identifier to multiplex different RTP streams, RTCP, and possibly other protocols. However, RoQ does not describe which protocol can be multiplexed with RoQ on the same QUIC connection. [I-D.draft-engelbart-quic-data-channels] describes a simple protocol similar to WebRTC data channels ([RFC8831]) called QUIC Data Channels (QDC). QDC uses QUIC instead of SCTP over DTLS and also uses an identifier similar to the one used by RoQ. This document describes how the two protocols can be multiplexed in one QUIC connection.

2. Connection Establishment

QUIC requires the use of ALPN [RFC7301] during connection setup. Connections multiplexing RoQ and QDC use the "roq-qdc-mux" token during the TLS handshake.

2.1. Draft version identification

  • RFC Editor's note: Please remove this section prior to publication of a final version of this document.

Only implementations of the final, published RFC can identify themselves as "roq-qdc-mux". Until such an RFC exists, implementations MUST NOT identify themselves using this string.

Implementations of draft versions of the protocol MUST add the string "-" and the corresponding draft number to the identifier. For example, draft-engelbart-multiplex-roq-qdc-04 is identified using the string "roq-qdc-mux-04".

Non-compatible experiments based on these draft versions MUST append the string "-" and an experiment name to the identifier.

3. Multiplexing

The two protocols for which this document describes a multiplexing scheme use a variable length integer as the first element on every QUIC stream and datagram. In RoQ, this integer is called a flow identifier, and it is used to multiplex different RTP streams and RTCP. In QDC, the integer is called a channel identifier and is used to multiplex multiple data channels.

This document describes two options for multiplexing RoQ and QDC. The first option builds upon the external signaling that is required by RoQ (Section 3.1). The second one works without any external signaling but places some restrictions on the chosen flow and channel identifiers (Section 3.2).

3.1. Multiplexing using External Signaling

RoQ requires using an external signaling protocol like the one described in [I-D.draft-dawkins-avtcore-sdp-rtp-quic]. The signaling includes the negotiation of flow identifiers for RoQ. In this scheme, applications MUST agree on all identifiers used by RoQ using the external signaling. Any identifier not assigned to a RoQ flow using external signaling MUST be treated as a QDC channel ID. Endpoints MUST NOT use an identifier for RoQ if it has not been signaled and agreed upon by both peers using the external signaling protocol.

3.2. Multiplexing without Signaling

When there is no external signaling for negotiation of identifiers available, endpoints can use the second least significant bit (0x02) of the flow or channel identifiers for multiplexing. RoQ flows have the bit set to 1, and QDC channels have the bit set to 0.

The second least significant bit is used instead of the least significant bit because the least significant bit already has a special function in QDC.

4. Error Handling

5. Security Considerations

The security considerations for the QUIC protocol and datagram extension described in Section 21 of [RFC9000], Section 9 of [RFC9001], Section 8 of [RFC9002] and Section 6 of [RFC9221] apply.

6. IANA Considerations

6.1. Registration of an ALPN Identification String

This document creates a new registration for the identification of the protocol in the "TLS Application-Layer Protocol Negotiation (ALPN) Protocol IDs" registry [RFC7301].

The "roq-qdc-mux" string identifies RoQ:


Multiplexed RoQ and QDC

Identification Sequence:



This document

7. References

7.1. Normative References

Ott, J., Engelbart, M., and S. Dawkins, "RTP over QUIC (RoQ)", Work in Progress, Internet-Draft, draft-ietf-avtcore-rtp-over-quic-07, , <>.
Friedl, S., Popov, A., Langley, A., and E. Stephan, "Transport Layer Security (TLS) Application-Layer Protocol Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, , <>.
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, , <>.
Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure QUIC", RFC 9001, DOI 10.17487/RFC9001, , <>.
Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection and Congestion Control", RFC 9002, DOI 10.17487/RFC9002, , <>.
Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable Datagram Extension to QUIC", RFC 9221, DOI 10.17487/RFC9221, , <>.

7.2. Informative References

Dawkins, S., "SDP Offer/Answer for RTP using QUIC as Transport", Work in Progress, Internet-Draft, draft-dawkins-avtcore-sdp-rtp-quic-00, , <>.
Jesup, R., Loreto, S., and M. Tüxen, "WebRTC Data Channels", RFC 8831, DOI 10.17487/RFC8831, , <>.


Authors' Addresses

Mathis Engelbart
Technical University Munich
Jörg Ott
Technical University Munich