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Document Type Active Internet-Draft (avtcore WG)
Authors Joerg Ott , Mathis Engelbart
Last updated 2023-02-20
Replaces draft-engelbart-rtp-over-quic
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Audio/Video Transport Core Maintenance                            J. Ott
Internet-Draft                                              M. Engelbart
Intended status: Standards Track             Technical University Munich
Expires: 24 August 2023                                 20 February 2023

                             RTP over QUIC


   This document specifies a minimal mapping for encapsulating Real-time
   Transport Protocol (RTP) and RTP Control Protocol (RTCP) packets
   within the QUIC protocol.  It also discusses how to leverage state
   from the QUIC implementation in the endpoints, in order to reduce the
   need to exchange RTCP packets and how to implement congestion control
   and rate adaptation without relying on RTCP feedback.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the Audio/Video Transport
   Core Maintenance Working Group mailing list (, which is
   archived at

   Source for this draft and an issue tracker can be found at

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 24 August 2023.

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Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Background  . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  What's in Scope for this Specification  . . . . . . . . .   4
     1.3.  What's Out of Scope for this Specification  . . . . . . .   5
   2.  Terminology and Notation  . . . . . . . . . . . . . . . . . .   6
   3.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Supported RTP Topologies  . . . . . . . . . . . . . . . .   8
   4.  Connection Establishment and ALPN . . . . . . . . . . . . . .   8
     4.1.  Draft version identification  . . . . . . . . . . . . . .   9
   5.  Encapsulation . . . . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  Multiplexing  . . . . . . . . . . . . . . . . . . . . . .   9
     5.2.  QUIC Streams  . . . . . . . . . . . . . . . . . . . . . .  10
     5.3.  QUIC Datagrams  . . . . . . . . . . . . . . . . . . . . .  12
   6.  RTCP  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  13
     6.1.  Transport Layer Feedback  . . . . . . . . . . . . . . . .  13
     6.2.  Application Layer Repair and other Control Messages . . .  16
   7.  Congestion Control and Rate Adaptation  . . . . . . . . . . .  17
     7.1.  Congestion Control at the QUIC layer  . . . . . . . . . .  17
     7.2.  Congestion Control at the Application Layer . . . . . . .  18
     7.3.  Shared QUIC connections . . . . . . . . . . . . . . . . .  19
   8.  API Considerations  . . . . . . . . . . . . . . . . . . . . .  19
     8.1.  Information to be exported from QUIC  . . . . . . . . . .  19
     8.2.  Functions to be exposed by QUIC . . . . . . . . . . . . .  20
   9.  Discussion  . . . . . . . . . . . . . . . . . . . . . . . . .  21
     9.1.  Flow Identifier . . . . . . . . . . . . . . . . . . . . .  21
     9.2.  Impact of Connection Migration  . . . . . . . . . . . . .  21
     9.3.  0-RTT considerations  . . . . . . . . . . . . . . . . . .  22
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  22
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  22
     11.1.  Registration of a RTP over QUIC Identification String  .  22
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  23
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  23

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     12.2.  Informative References . . . . . . . . . . . . . . . . .  25
   Appendix A.  Experimental Results . . . . . . . . . . . . . . . .  27
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  27
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

1.  Introduction

   This document specifies a minimal mapping for encapsulating Real-time
   Transport Protocol (RTP) [RFC3550] and RTP Control Protocol (RTCP)
   [RFC3550] packets within the QUIC protocol ([RFC9000]).  It also
   discusses how to leverage state from the QUIC implementation in the
   endpoints, in order to reduce the need to exchange RTCP packets, and
   how to implement congestion control and rate adaptation without
   relying on RTCP feedback.

1.1.  Background

   The Real-time Transport Protocol (RTP) [RFC3550] is generally used to
   carry real-time media for conversational media sessions, such as
   video conferences, across the Internet.  Since RTP requires real-time
   delivery and is tolerant to packet losses, the default underlying
   transport protocol has been UDP, recently with DTLS on top to secure
   the media exchange and occasionally TCP (and possibly TLS) as a

   This specification describes an application usage of QUIC
   ([RFC9308]).  As a baseline, the specification does not expect more
   than a standard QUIC implementation as defined in [RFC8999],
   [RFC9000], [RFC9001], and [RFC9002], providing a secure end-to-end
   transport that is also expected to work well through NATs and
   firewalls.  Beyond this baseline, real-time applications can benefit
   from QUIC extensions such as unreliable QUIC datagrams [RFC9221],
   which provides additional desirable properties for real-time traffic
   (e.g., no unnecessary retransmissions, avoiding head-of-line

   Moreover, with QUIC's multiplexing capabilities, reliable and
   unreliable transport connections as, e.g., needed for WebRTC, can be
   established with only a single port used at either end of the

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1.2.  What's in Scope for this Specification

   This document defines a mapping for RTP and RTCP over QUIC (this
   mapping is hereafter referred to as "RTP-over-QUIC"), and describes
   ways to reduce the amount of RTCP traffic by leveraging state
   information readily available within a QUIC endpoint.  This document
   also describes different options for implementing congestion control
   and rate adaptation for RTP over QUIC.

   This specification focuses on providing a secure encapsulation of RTP
   packets for transmission over QUIC.  The expected usage is wherever
   RTP is used to carry media packets, allowing QUIC in place of other
   transport protocols such as TCP, UDP, SCTP, DTLS, etc.  That is, we
   expect RTP-over-QUIC to be used in contexts in which a signaling
   protocol is used to announce or negotiate a media encapsulation and
   the associated transport parameters (such as IP address, port
   number).  RTP-over-QUIC is not intended as a stand-alone media
   transport, although QUIC transport parameters could be statically

   The above implies that RTP-over-QUIC is targeted at peer-to-peer
   operation; but it may also be used in client-server-style settings,
   e.g., when talking to a conference server as described in RFC 7667
   ([RFC7667]), or, if RTP-over-QUIC is used to replace RTSP
   ([RFC7826]), to a media server.

   Moreover, this document describes how a QUIC implementation and its
   API can be extended to improve efficiency of the RTP-over-QUIC
   protocol operation.

   RTP-over-QUIC does not impact the usage of RTP Audio Video Profiles
   (AVP) ([RFC3551]), or any RTP-based mechanisms, even though it may
   render some of them unnecessary, e.g., Secure Real-Time Transport
   Prococol (SRTP) ([RFC3711]) might not be needed, because end-to-end
   security is already provided by QUIC, and double encryption by QUIC
   and by SRTP might have more costs than benefits.  Nor does RTP-over-
   QUIC limit the use of RTCP-based mechanisms, even though some
   information or functions obtained by using RTCP mechanisms may also
   be available from the underlying QUIC implementation by other means.

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   Between two (or more) endpoints, RTP-over-QUIC supports multiplexing
   multiple RTP-based media streams within a single QUIC connection and
   thus using a single (destination IP address, destination port number,
   source IP address, source port number, protocol) 5-tuple..  We note
   that multiple independent QUIC connections may be established in
   parallel using the same destination IP address, destination port
   number, source IP address, source port number, protocol) 5-tuple.,
   e.g. to carry different media channels.  These connections would be
   logically independent of one another.

1.3.  What's Out of Scope for this Specification

   This document does not attempt to enhance QUIC for real-time media or
   define a replacement for, or evolution of, RTP.  Work to map other
   media transport protocols to QUIC is under way elsewhere in the IETF.

   RTP-over-QUIC is designed for use with point-to-point connections,
   because QUIC itself is not defined for multicast operation.  The
   scope of this document is limited to unicast RTP/RTCP, even though
   nothing would or should prevent its use in multicast setups once QUIC
   supports multicast.

   RTP-over-QUIC does not define congestion control and rate adaptation
   algorithms for use with media.  However, Section 7 discusses options
   for how congestion control and rate adaptation could be performed at
   the QUIC and/or at the RTP layer, and how information available at
   the QUIC layer could be exposed via an API for the benefit of RTP
   layer implementation.

      *Editor's note:* Need to check whether Section 7 will also
      describe the QUIC interface that's being exposed, or if that ends
      up somewhere else in the document.

   RTP-over-QUIC does not define prioritization mechanisms when handling
   different media as those would be dependent on the media themselves
   and their relationships.  Prioritization is left to the application
   using RTP-over-QUIC.

   This document does not cover signaling for session setup.  SDP for
   RTP-over-QUIC is defined in separate documents such as
   [I-D.draft-dawkins-avtcore-sdp-rtp-quic], and can be carried in any
   signaling protocol that can carry SDP, including the Session
   Initiation Protocol (SIP) ([RFC3261]), Real-Time Protocols for
   Browser-Based Applications (RTCWeb) ([RFC8825]), or WebRTC-HTTP
   Ingestion Protocol (WHIP) ([I-D.draft-ietf-wish-whip]).

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2.  Terminology and Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

      *Editor's note:* the list of terms below will almost certainly
      grow in size as the specification matures.

   The following terms are used:

   Congestion Control:  A mechanism to limit the aggregate amount of
      data that has been sent over a path to a receiver, but has not
      been acknowledged by the receiver.  This prevents a sender from
      overwhelming the capacity of a path between a sender and a
      receiver, causing some outstanding data to be discarded before the
      receiver can receive the data and acknowledge it to the sender.

   Datagram:  Datagrams exist in UDP as well as in QUIC's unreliable
      datagram extension.  If not explicitly noted differently, the term
      datagram in this document refers to a QUIC Datagram as defined in

   Endpoint:  A QUIC server or client that participates in an RTP over
      QUIC session.

   Frame:  A QUIC frame as defined in [RFC9000].

   Media Encoder:  An entity that is used by an application to produce a
      stream of encoded media, which can be packetized in RTP packets to
      be transmitted over QUIC.

   Rate Adaptation:  A mechanism to help a sender determine and adjust
      its sending rate, in order to maximize the amount of information
      that is sent to a receiver, without causing queues to build beyond
      a reasonable amount, causing "buffer bloat" and "jitter".  Rate
      adapation is one way to accomplish congestion control for realtime
      media, especially when a sender has multiple media streams to the
      receiver, because the sum of all sending rates for media streams
      must not be high enough to cause congestion on the path these
      media streams share between sender and receiver.

   Receiver:  An endpoint that receives media in RTP packets and may
      send or receive RTCP packets.

   Sender:  An endpoint that sends media in RTP packets and may send or

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      receive RTCP packets.

   Packet diagrams in this document use the format defined in
   Section 1.3 of [RFC9000] to illustrate the order and size of fields.

3.  Protocol Overview

   This document introduces a mapping of the Real-time Transport
   Protocol (RTP) to the QUIC transport protocol.  RTP over QUIC allows
   the use of QUIC streams and QUIC datagrams to transport real-time
   data, and thus, the QUIC implementation MUST support QUIC's datagram
   extension, if RTP packets should be sent over QUIC datagrams.  Since
   datagram frames cannot be fragmented, the QUIC implementation MUST
   also provide a way to query the maximum datagram size so that an
   application can create RTP packets that always fit into a QUIC
   datagram frame.

   [RFC3550] specifies that RTP sessions need to be transmitted on
   different transport addresses to allow multiplexing between them.
   RTP over QUIC uses a different approach to leverage the advantages of
   QUIC connections without managing a separate QUIC connection per RTP
   session.  QUIC does not provide demultiplexing between different
   flows on datagrams but suggests that an application implement a
   demultiplexing mechanism if required.  An example of such a mechanism
   are flow identifiers prepended to each datagram frame as described in
   Section 2.1 of [I-D.draft-ietf-masque-h3-datagram].  RTP over QUIC
   uses a flow identifier to replace the network address and port number
   to multiplex many RTP sessions over the same QUIC connection.

   A rate adaptation algorithm can be plugged in to adapt the media
   bitrate to the available bandwidth.  This document does not mandate
   any specific rate adaptation algorithm.  Some examples include
   Network-Assisted Dynamic Adaptation (NADA) [RFC8698] and Self-Clocked
   Rate Adaptation for Multimedia (SCReAM) [RFC8298].  These rate
   adaptation algorithms require some feedback about the network's
   performance to calculate target bitrates.  Traditionally this
   feedback is generated at the receiver and sent back to the sender via
   RTCP.  Since QUIC also collects some metrics about the network's
   performance, these metrics can be used to generate the required
   feedback at the sender-side and provide it to the rate adaptation
   algorithm to avoid the additional overhead of the RTCP stream.

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3.1.  Supported RTP Topologies

   RTP over QUIC only supports some of the RTP topologies described in
   [RFC7667].  Most notably, due to QUIC being a purely unicast protocol
   at the time of writing, RTP over QUIC cannot be used as a transport
   protocol in any of the multicast topologies (e.g., _Topo-ASM_, _Topo-
   SSM_, _Topo-SSM-RAMS_).

   RTP supports different types of translators and mixers.  Whenever a
   middlebox such as a translator or a mixer needs to access the content
   of RTP/RTCP-packets, the QUIC connection has to be terminated at that

   Using RTP over QUIC streams (see Section 5.2) can support much larger
   RTP packet sizes than other transport protocols such as UDP can,
   which can lead to problems with transport translators which translate
   from RTP over QUIC to RTP over a different transport protocol.  A
   similar problem can occur if a translator needs to translate from RTP
   over UDP to RTP over QUIC datagrams, where the MTU of a QUIC datagram
   may be smaller than the MTU of a UDP datagram.  In both cases, the
   translator may need to rewrite the RTP packets to fit into the
   smaller MTU of the other protocol.  Such a translator may need codec-
   specific knowledge to packetize the payload of the incoming RTP
   packets in smaller RTP packets.

4.  Connection Establishment and ALPN

   QUIC requires the use of ALPN [RFC7301] tokens during connection
   setup.  RTP over QUIC uses "rtp-mux-quic" as ALPN token in the TLS
   handshake (see also Section 11.

   Note that the use of a given RTP profile is not reflected in the ALPN
   token even though it could be considered part of the application
   usage.  This is simply because different RTP sessions, which may use
   different RTP profiles, may be carried within the same QUIC

      *Editor's note:* "rtp-mux-quic" indicates that RTP and other
      protocols may be multiplexed on the same QUIC connection using a
      flow identifier as described in Section 5.  Applications are
      responsible for negotiation of protocols in use by appropriate use
      of a signaling protocol such as SDP.

      *Editor's note:* This implies that applications cannot use RTP
      over QUIC as specified in this document over WebTransport.

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4.1.  Draft version identification

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

   RTP over QUIC uses the token "rtp-mux-quic" to identify itself in

   Only implementations of the final, published RFC can identify
   themselves as "rtp-mux-quic".  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-ietf-avtcore-rtp-over-quic-04 is identified using the
   string "rtp-mux-quic-04".

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

5.  Encapsulation

   This section describes the encapsulation of RTP/RTCP packets in QUIC.

   QUIC supports two transport methods: streams [RFC9000] and datagrams
   [RFC9221].  This document specifies mappings of RTP to both of the
   transport modes.  Senders MAY combine both modes by sending some RTP/
   RTCP packets over the same or different QUIC streams and others in
   QUIC datagrams.

   Section 5.1 introduces a multiplexing mechanism that supports
   multiplexing RTP, RTCP, and, with some constraints, other non-RTP
   protocols.  Section 5.2 and Section 5.3 explain the specifics of
   mapping RTP to QUIC streams and QUIC datagrams, respectively.

5.1.  Multiplexing

   RTP over QUIC uses flow identifiers to multiplex different RTP, RTCP,
   and non-RTP data streams on a single QUIC connection.  A flow
   identifier is a QUIC variable-length integer as described in
   Section 16 of [RFC9000].  Each flow identifier is associated with a
   stream of RTP packets, RTCP packets, or a data stream of a non-RTP

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   In a QUIC connection using the ALPN token defined in Section 4, every
   QUIC datagram and every QUIC stream MUST start with a flow
   identifier.  A peer MUST NOT send any data in a datagram or stream
   that is not associated with the flow identifier which started the
   datagram or stream.

   RTP and RTCP packets of different RTP sessions MUST use distinct flow
   identifiers.  If peers wish to send multiple types of media in a
   single RTP session, they MAY do so by following [RFC8860].

   A single RTP session MAY be associated with one or two flow
   identifiers.  Thus, it is possible to send RTP and RTCP packets
   belonging to the same session using different flow identifiers.  RTP
   and RTCP packets of a single RTP session MAY use the same flow
   identifier (following the procedures defined in [RFC5761], or they
   MAY use different flow identifiers.

   The association between flow identifiers and data streams MUST be
   negotiated using appropriate signaling.  Applications MAY send data
   using flow identifiers not associated with any RTP or RTCP stream.
   If a receiver cannot associate a flow identifier with any RTP/RTCP or
   non-RTP stream, it MAY drop the data stream.

   There are different use cases for sharing the same QUIC connection
   between RTP and non-RTP data streams.  Peers might use the same
   connection to exchange signaling messages or exchange data while
   sending and receiving media streams.  The semantics of non-RTP
   datagrams or streams are not in the scope of this document.  Peers
   MAY use any protocol on top of the encapsulation described in this

   Flow identifiers introduce some overhead in addition to the header
   overhead of RTP/RTCP and QUIC.  QUIC variable-length integers require
   between one and eight bytes depending on the number expressed.  Thus,
   it is advisable to use low numbers first and only use higher ones if
   necessary due to an increased number of flows.

5.2.  QUIC Streams

   To send RTP/RTCP packets over QUIC streams, a sender MUST open a new
   unidirectional QUIC stream.  Streams are unidirectional because there
   is no synchronous relationship between sent and received RTP/RTCP
   packets.  A sender MAY open new QUIC streams for different packets
   using the same flow identifier, for example, to avoid head-of-line

   Figure 1 shows the encapsulation format for RTP over QUIC Streams.

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   Payload {
     Flow Identifier (i),
     RTP/RTCP Payload(..) ...,

               Figure 1: RTP over QUIC Streams Payload Format

   Flow Identifier:  Flow identifier to demultiplex different data flows
      on the same QUIC connection.

   RTP/RTCP Payload:  Contains the RTP/RTCP payload; see Figure 2

   The payload in a QUIC stream starts with the flow identifier followed
   by one or more RTP/RTCP payloads.  All RTP/RTCP payloads sent on a
   stream MUST belong to the RTP session with the same flow identifier.

   Each payload begins with a length field indicating the length of the
   RTP/RTCP packet, followed by the packet itself, see Figure 2.

   RTP/RTCP Payload {
     RTP/RTCP Packet(..),

                Figure 2: RTP/RTCP payload for QUIC streams

   Length:  A QUIC variable length integer Section 16 of [RFC9000]
      describing the length of the following RTP/RTCP packets in bytes.

   RTP/RTCP Packet:  The RTP/RTCP packet to transmit.

   If a sender knows that a packet, which was not yet successfully and
   completely transmitted, is no longer needed, the sender MAY close the
   stream by sending a RESET_STREAM frame.

   A translator that translates between two endpoints, both connected
   via QUIC, MUST forward RESET_STREAM frames received from one end to
   the other unless it forwards the RTP packets on QUIC datagrams.

      *Editor's Note:* It might be desired to also allow the receiver to
      request cancellation of a stream by sending STOP_SENDING frame.
      However, this might lead to unintended packet loss because the
      receiver does not know which and how many packets follow on the
      same stream.  If this feature is required, a solution could be to
      require senders to open new streams for each application data
      unit, as described in a previous version of this document.

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   Large RTP packets sent on a stream will be fragmented into smaller
   QUIC frames.  The QUIC frames are transmitted reliably and in order
   such that a receiving application can read a complete RTP packet from
   the stream as long as the stream is not closed with a RESET_STREAM
   frame.  No retransmission has to be implemented by the application
   since QUIC frames lost in transit are retransmitted by QUIC.

   Opening new streams for new packets MAY implicitly limit the number
   of packets concurrently in transit because the QUIC receiver provides
   an upper bound of parallel streams, which it can update using QUIC
   MAX_STREAMS frames.  The number of packets that have to be
   transmitted concurrently depends on several factors, such as the
   number of RTP streams within a QUIC connection, the bitrate of the
   media streams, and the maximum acceptable transmission delay of a
   given packet.  Receivers are responsible for providing senders with
   enough credit to open new streams for new packets at any time.

5.3.  QUIC Datagrams

   Senders can also transmit RTP packets in QUIC datagrams.  QUIC
   datagrams are an extension to QUIC described in [RFC9221].  QUIC
   datagrams preserve frame boundaries.  Thus, a single RTP packet can
   be mapped to a single QUIC datagram without additional framing.
   Senders SHOULD consider the header overhead associated with QUIC
   datagrams and ensure that the RTP/RTCP packets, including their
   payloads, flow identifier, QUIC, and IP headers, will fit into path

   Figure 3 shows the encapsulation format for RTP over QUIC Datagrams.

   Payload {
     Flow Identifier (i),
     RTP/RTCP Packet (..),

              Figure 3: RTP over QUIC Datagram Payload Format

   Flow Identifier:  Flow identifier to demultiplex different data flows
      on the same QUIC connection.

   RTP/RTCP Packet:  The RTP/RTCP packet to transmit.

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   Since QUIC datagrams are not retransmitted on loss (see also
   Section 6.1 for loss signaling), if an application wishes to
   retransmit lost RTP packets, the retransmission has to be implemented
   by the application.  RTP retransmissions can be done in the same RTP
   session or a separate RTP session [RFC4588] and the flow identifier
   MUST be set to the flow identifier of the RTP session in which the
   retransmission happens.

6.  RTCP

   The RTP Control Protocol (RTCP) allows RTP senders and receivers to
   exchange control information to monitor connection statistics and to
   identify and synchronize streams.  Many of the statistics contained
   in RTCP packets overlap with the connection statistics collected by a
   QUIC connection.  To avoid using up bandwidth for duplicated control
   information, the information SHOULD only be sent at one protocol
   layer.  QUIC relies on certain control frames to be sent.

   In general, applications MAY send RTCP without any restrictions.
   This document specifies a baseline for replacing some of the RTCP
   packet types by mapping the contents to QUIC connection statistics.
   Future documents can extend this mapping for other RTCP format types.
   It is RECOMMENDED to expose relevant information from the QUIC layer
   to the application instead of exchanging additional RTCP packets,
   where applicable.

   This section discusses what information can be exposed from the QUIC
   connection layer to reduce the RTCP overhead and which type of RTCP
   messages cannot be replaced by similar feedback from the transport
   layer.  The list of RTCP packets in this section is not exhaustive
   and similar considerations SHOULD be taken into account before
   exchanging any other type of RTCP control packets.

6.1.  Transport Layer Feedback

   This section explains how some of the RTCP packet types which are
   used to signal reception statistics can be replaced by equivalent
   statistics that are already collected by QUIC.  The following list
   explains how this mapping can be achieved for the individual fields
   of different RTCP packet types.

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   QUIC Datagrams are ack-eliciting packets, which means, that an
   acknowledgment is triggered when a datagram frame is received.  Thus,
   a sender can assume that an RTP packet arrived at the receiver or was
   lost in transit, using the QUIC acknowledgments of QUIC Datagram
   frames.  In the following, an RTP packet is regarded as acknowledged,
   when the QUIC Datagram frame that carried the RTP packet, was
   acknowledged.  For RTP packets that are sent over QUIC streams, an
   RTP packet can be considered acknowledged, when all frames which
   carried fragments of the RTP packet were acknowledged.

   When QUIC Streams are used, the application should be aware that the
   direct mapping proposed below may not reflect the real
   characteristics of the network.  RTP packet loss can seem lower than
   actual packet loss due to QUIC's automatic retransmissions.
   Similarly, timing information might be incorrect due to

   Some of the transport layer feedback that can be implemented in RTCP
   contains information that is not included in QUIC by default, but can
   be added via QUIC extensions.  One important example are arrival
   timestamps, which are not part of QUIC's default acknowledgment
   frames, but can be added using [I-D.draft-smith-quic-receive-ts] or
   [I-D.draft-huitema-quic-ts].  Another extension, that can improve the
   precision of the feedback from QUIC is
   [I-D.draft-ietf-quic-ack-frequency], which allows a sender to control
   the delay of acknowledgments sent by the receiver.

   The list of RTCP Receiver Reports that could be replaced by feedback
   from QUIC follows:

   *  _Receiver Reports_ (PT=201, Name=RR, [RFC3550])

      -  _Fraction lost_: When RTP packets are carried in QUIC
         datagrams, the fraction of lost packets can be directly
         inferred from QUIC's acknowledgments.  The calculation SHOULD
         include all packets up to the acknowledged RTP packet with the
         highest RTP sequence number.  Later packets SHOULD be ignored,
         since they may still be in flight, unless other QUIC packets
         that were sent after the RTP packet, were already acknowledged.

      -  _Cumulative lost_: Similar to the fraction of lost packets, the
         cumulative loss can be inferred from QUIC's acknowledgments
         including all packets up to the latest acknowledged packet.

      -  _Highest Sequence Number received_: In RTCP, this field is a
         32-bit field that contains the highest sequence number a
         receiver received in an RTP packet and the count of sequence
         number cycles the receiver has observed.  A sender sends RTP

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         packets in QUIC packets and receives acknowledgments for the
         QUIC packets.  By keeping a mapping from a QUIC packet to the
         RTP packets encapsulated in that QUIC packet, the sender can
         infer the highest sequence number and number of cycles seen by
         the receiver from QUIC acknowledgments.

      -  _Interarrival jitter_: If QUIC acknowledgments carry timestamps
         as described in one of the extensions referenced above, senders
         can infer from QUIC acks the interarrival jitter from the
         arrival timestamps.

      -  _Last SR_: Similar to RTP arrival times, the arrival time of
         RTCP Sender Reports can be inferred from QUIC acknowledgments,
         if they include timestamps.

      -  _Delay since last SR_: This field is not required when the
         receiver reports are entirely replaced by QUIC feedback.

   *  _Negative Acknowledgments_ (PT=205, FMT=1, Name=Generic NACK,

      -  The generic negative acknowledgment packet contains information
         about packets which the receiver considered lost.
         Section 6.2.1. of [RFC4585] recommends to use this feature
         only, if the underlying protocol cannot provide similar
         feedback.  QUIC does not provide negative acknowledgments, but
         can detect lost packets based on the Gap numbers contained in
         QUIC ACK frames Section 6 of [RFC9002].

   *  _ECN Feedback_ (PT=205, FMT=8, Name=RTCP-ECN-FB, [RFC6679])

      -  ECN feedback packets report the count of observed ECN-CE marks.
         [RFC6679] defines two RTCP reports, one packet type (with
         PT=205 and FMT=8) and a new report block for the extended
         reports which are listed below.  QUIC supports ECN reporting
         through acknowledgments.  If the connection supports ECN, the
         reporting of ECN counts SHOULD be done using QUIC
         acknowledgments, rather than RTCP ECN feedback reports.

   *  _Congestion Control Feedback_ (PT=205, FMT=11, Name=CCFB,

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      -  RTP Congestion Control Feedback contains acknowledgments,
         arrival timestamps and ECN notifications for each received
         packet.  Acknowledgments and ECNs can be inferred from QUIC as
         described above.  Arrival timestamps can be added through
         extended acknowledgment frames as described in
         [I-D.draft-smith-quic-receive-ts] or

   *  _Extended Reports_ (PT=207, Name=XR, [RFC3611])

      -  Extended Reports offer an extensible framework for a variety of
         different control messages.  Some of the standard report blocks
         which can be implemented in extended reports such as loss RLE
         or ECNs can be implemented in QUIC, too.  For other report
         blocks, it SHOULD be evaluated individually, if the contained
         information can be transmitted using QUIC instead.

6.2.  Application Layer Repair and other Control Messages

   While the previous section presented some RTCP packet that can be
   replaced by QUIC features, QUIC cannot replace all of the available
   RTCP packet types.  This mostly affects RTCP packet types which carry
   control information that is to be interpreted by the application
   layer instead of the transport itself.

   _Sender Reports_ (PT=200, Name=SR, [RFC3550]) are similar to
   _Receiver Reports_. They are sent by media senders and additionally
   contain a NTP and a RTP timestamp and the number of packets and
   octets transmitted by the sender.  The timestamps can be used by a
   receiver to synchronize streams.  QUIC cannot provide a similar
   control information, since it does not know about RTP timestamps.
   Nor can a QUIC receiver calculate the packet or octet counts, since
   it does not know about lost datagrams.  Thus, sender reports are
   required in RTP over QUIC to synchronize streams at the receiver.
   The sender reports SHOULD not contain any receiver report blocks, as
   the information can be inferred from the QUIC transport as explained
   in the previous section.

   Next to carrying transmission statistics, RTCP packets can contain
   application layer control information, that cannot directly be mapped
   to QUIC.  This includes for example the _Source Description_ (PT=202,
   Name=SDES), _Bye_ (PT=203, Name=BYE) and _Application_ (PT=204,
   Name=APP) packet types from [RFC3550] or many of the payload specific
   feedback messages (PT=206) defined in [RFC4585], which can for
   example be used to control the codec behavior of the sender.  Since
   QUIC does not provide any kind of application layer control
   messaging, these RTCP packet types SHOULD be used in the same way as
   they would be used over any other transport protocol.

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7.  Congestion Control and Rate Adaptation

   Like any other application on the internet, RTP over QUIC needs to
   perform congestion control to avoid overloading the network.

   QUIC is a congestion controlled transport protocol.  Senders are
   required to employ some form of congestion control.  The default
   congestion control specified for QUIC in [RFC9002] is similar to TCP
   NewReno [RFC6582], but senders are free to choose any congestion
   control algorithm as long as they follow the guidelines specified in
   Section 3 of [RFC8085].

   RTP itself does not specify a congestion control algorithm, but
   [RFC8888] defines an RTCP feedback message intended to enable rate
   adaptation for interactive real-time traffic using RTP, and
   successful rate adaptation will accomoplish congestion control as
   well.  Various rate adaptation algorithms for real-time media are
   defined in separate RFCs (e.g.  SCReAM [RFC8298] and NADA [RFC8698]).
   The rate adaptation algorithms for RTP are specifically tailored for
   real-time transmissions at low latencies.  The available rate
   adaptation algorithms for RTP expose a target_bitrate that can be
   used to dynamically reconfigure media codecs to produce media at a
   rate that can be sent in real-time under the observed network

   This section defines two architectures for congestion control and
   bandwidth estimation for RTP over QUIC, but it does not mandate any
   specific rate adaptation algorithm to use.  The section also
   discusses congestion control implications of using shared or multiple
   separate QUIC connections to send and receive multiple independent
   data streams.

   It is assumed that the congestion controller in use provides a pacing
   mechanism to determine when a packet can be sent to avoid bursts.
   The currently proposed congestion control algorithms for real-time
   communications provide such pacing mechanisms.  The use of congestion
   controllers which don't provide a pacing mechanism is out of scope of
   this document.

7.1.  Congestion Control at the QUIC layer

   If congestion control is to be applied at the transport layer, it is
   RECOMMENDED that the QUIC Implementation uses a congestion controller
   that keeps queueing delays short to keep the transmission latency for
   RTP and RTCP packets as low as possible.

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   Many low latency congestion control algorithms depend on detailed
   arrival time feedback to estimate the current one-way delay between
   sender and receiver.  QUIC does not provide arrival timestamps in its
   acknowledgments.  The QUIC implementations of the sender and receiver
   can use an extension to add this information to QUICs acknowledgment
   frames, e.g.  [I-D.draft-smith-quic-receive-ts] or

   If congestion control is done by the QUIC implementation, the
   application needs a mechanism to query the currently available
   bandwidth to adapt media codec configurations.  The employed
   congestion controller of the QUIC connection SHOULD expose such an
   API to the application.  If a current bandwidth estimate is not
   available from the QUIC congestion controller, the sender can either
   implement an alternative bandwidth estimation at the application
   layer as described in Section 7.2 or a receiver can feedback the
   observed bandwidth through RTCP, e.g., using

7.2.  Congestion Control at the Application Layer

   If an application cannot access a bandwidth estimation from the QUIC
   layer, or the QUIC implementation does not support a delay-based,
   low-latency congestion control algorithm, the application can
   alternatively implement a bandwidth estimation algorithm at the
   application layer.  Calculating a bandwidth estimation at the
   application layer can be done using the same bandwidth estimation
   algorithms as described in Section 7 (NADA, SCReAM).  The bandwidth
   estimation algorithm typically needs some feedback on the
   transmission performance.  This feedback can be collected following
   the guidelines in Section 6.

   If the application implements full congestion control rather than
   just a bandwidth estimation at the application layer using a
   congestion controller that satisfies the requirements of Section 7 of
   [RFC9002], and the connection is only used to send real-time media
   which is subject to the application layer congestion control, it is
   RECOMMENDED to disable any other congestion control that is possibly
   running at the QUIC layer.  Disabling the additional congestion
   controllers helps to avoid any interference between the different
   congestion controllers.

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7.3.  Shared QUIC connections

   Two endpoints may want to establish channels to exchange more than
   one type of data simultaneously.  The channels can be intended to
   carry real-time RTP data or other non-real-time data.  This can be
   realized in different ways.  A straightforward solution is to
   establish multiple QUIC connections, one for each channel.  Or all
   real-time channels are mapped to one QUIC connection, while a
   separate QUIC connection is created for the non-real-time channels.
   In both cases, the congestion controllers can be chosen to match the
   demands of the respective channels and the different QUIC connections
   will compete for the same resources in the network.  No local
   prioritization of data across the different (types of) channels would
   be necessary.

   Alternatively, (all or a subset of) real-time and non-real-time
   channels are multiplexed onto a single, shared QUIC connection, which
   can be done by using the flow identifier described in Section 5.
   Applications multiplexing multiple streams in one connection SHOULD
   implement some form of stream prioritization or bandwidth allocation.

8.  API Considerations

   The mapping described in the previous sections poses some interface
   requirements on the QUIC implementation.  Although a basic mapping
   should work without any of these requirements most of the
   optimizations regarding rate adaptation and RTCP mapping require
   certain functionalities to be exposed to the application.  The
   following to sections contain a list of information that is required
   by an application to implement different optimizations (Section 8.1)
   and functions that a QUIC implementation SHOULD expose to an
   application (Section 8.2).

   Each item in the following list can be considered individually.  Any
   exposed information or function can be used by RTP over QUIC
   regardless of whether the other items are available.  Thus, RTP over
   QUIC does not depend on the availability of all of the listed
   features but can apply different optimizations depending on the
   functionality exposed by the QUIC implementation.

8.1.  Information to be exported from QUIC

   This section provides a list of items that an application might want
   to export from an underlying QUIC implementation.  It is thus
   RECOMMENDED that a QUIC implementation exports the listed items to
   the application.

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   *  _Maximum Datagram Size_: The maximum datagram size that the QUIC
      connection can transmit.

   *  _Datagram Acknowledgment and Loss_: Section 5.2 of [RFC9221]
      allows QUIC implementations to notify the application that a QUIC
      Datagram was acknowledged or that it believes a datagram was lost.
      The exposed information SHOULD include enough information to allow
      the application to maintain a mapping between the datagram that
      was acknowledged/lost and the RTP packet that was sent in that

   *  _Stream States_: The QUIC implementation SHOULD expose to a
      sender, how much of the data that was sent on a stream was
      successfully delivered and how much data is still outstanding to
      be sent or retransmitted.

   *  _Arrival timestamps_: If the QUIC connection uses a timestamp
      extension like [I-D.draft-smith-quic-receive-ts] or
      [I-D.draft-huitema-quic-ts], the arrival timestamps or one-way
      delays SHOULD be exposed to the application.

   *  _Bandwidth Estimation_: If congestion control is done at the
      transport layer in the QUIC implementation, the QUIC
      implementation SHOULD expose an estimation of the currently
      available bandwidth to the application.  Exposing the bandwidth
      estimation avoids the implementation of an additional bandwidth
      estimation algorithm in the application.

   *  _ECN_: If ECN marks are available, they SHOULD be exposed to the

8.2.  Functions to be exposed by QUIC

   This sections lists functions that a QUIC implementation SHOULD
   expose to an application to implement different features of the
   mapping described in the previous sections of this document.

   *  _Cancel Streams_: To allow an application to cancel
      (re)transmission of packets that are no longer needed, the QUIC
      implementation MUST expose a way to cancel the corresponding QUIC

   *  _Configure Congestion Controller_: If congestion control is to be
      implemented at the QUIC connection layer as described in
      Section 7.1, the QUIC implementation SHOULD expose an API to allow
      the application to configure the specifics of the congestion

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   *  _Disable Congestion Controller_: If congestion control is to be
      implemented at the application layer as described in Section 7.2,
      and the application layer is trusted to apply adequate congestion
      control as described in Section 7 of [RFC9002] and Section 3.1 of
      [RFC8085], it is RECOMMENDED to allow the application to disable
      QUIC layer congestion control entirely.

9.  Discussion

9.1.  Flow Identifier

   [RFC9221] suggests to use flow identifiers to multiplex different
   streams on QUIC Datagrams, which is implemented in Section 5, but it
   is unclear how applications can combine RTP over QUIC with other data
   streams using the same QUIC connections.  If the non-RTP data streams
   use the same flow identifies, too and the application can make sure,
   that flow identifiers are unique, there should be no problem.  Flow
   identifiers could be problematic, if different specifications for RTP
   and non-RTP data streams over QUIC mandate different incompatible
   flow identifiers.

9.2.  Impact of Connection Migration

   RTP sessions are characterized by a continuous flow of packets into
   either or both directions.  A connection migration may lead to
   pausing media transmission until reachability of the peer under the
   new address is validated.  This may lead to short breaks in media
   delivery in the order of RTT and, if RTCP is used for RTT
   measurements, may cause spikes in observed delays.  Application layer
   congestion control mechanisms (and also packet repair schemes such as
   retransmissions) need to be prepared to cope with such spikes.

   If a QUIC connection is established via a signaling channel, this
   signaling may have involved Interactive Connectivity Establishment
   (ICE) exchanges to determine and choose suitable (IP address, port
   number) pairs for the QUIC connection.  Subsequent address change
   events may be noticed by QUIC via its connection migration handling
   and/or at the ICE or other application layer, e.g., by noticing
   changing IP addresses at the network interface.  This may imply that
   the two signaling and data "layers" get (temporarily) out of sync.

      *Editor's Note:* It may be desirable that the API provides an
      indication of connection migration event for either case.

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9.3.  0-RTT considerations

   For repeated connections between peers, the initiator of a QUIC
   connection can use 0-RTT data for both QUIC streams and datagrams.
   As such packets are subject to replay attacks, applications shall
   carefully specify which data types and operations are allowed.  0-RTT
   data may be beneficial for use with RTP over QUIC to reduce the risk
   of media clipping, e.g., at the beginning of a conversation.

   This specification defines carrying RTP on top of QUIC and thus does
   not finally define what the actual application data are going to be.
   RTP typically carries ephemeral media contents that is rendered and
   possibly recorded but otherwise causes no side effects.  Moreover,
   the amount of data that can be carried as 0-RTT data is rather
   limited.  But it is the responsibility of the respective application
   to determine if 0-RTT data is permissible.

      *Editor's Note:* Since the QUIC connection will often be created
      in the context of an existing signaling relationship (e.g., using
      WebRTC or SIP), specific 0-RTT keying material could be exchanged
      to prevent replays across sessions.  Within the same connection,
      replayed media packets would be discarded as duplicates by the

10.  Security Considerations

   RTP over QUIC is subject to the security considerations of RTP
   described in Section 9 of [RFC3550] and the security considerations
   of any RTP profile in use.

   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] also
   apply to RTP over QUIC.

11.  IANA Considerations

11.1.  Registration of a RTP over QUIC Identification String

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

   The "rtp-mux-quic" string identifies RTP over QUIC:

   Protocol:  RTP over QUIC

   Identification Sequence:  0x72 0x74 0x70 0x2D 0x6F 0x76 0x65 0x72

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      0x2D 0x71 0x75 0x69 0x63 ("rtp-mux-quic")

   Specification:  This document

12.  References

12.1.  Normative References

              Huitema, C., "Quic Timestamps For Measuring One-Way
              Delays", Work in Progress, Internet-Draft, draft-huitema-
              quic-ts-08, 28 August 2022,

              Iyengar, J. and I. Swett, "QUIC Acknowledgement
              Frequency", Work in Progress, Internet-Draft, draft-ietf-
              quic-ack-frequency-02, 11 July 2022,

              Smith, C. and I. Swett, "QUIC Extension for Reporting
              Packet Receive Timestamps", Work in Progress, Internet-
              Draft, draft-smith-quic-receive-ts-00, 25 October 2021,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
              July 2003, <>.

   [RFC3551]  Schulzrinne, H. and S. Casner, "RTP Profile for Audio and
              Video Conferences with Minimal Control", STD 65, RFC 3551,
              DOI 10.17487/RFC3551, July 2003,

   [RFC3611]  Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed.,
              "RTP Control Protocol Extended Reports (RTCP XR)",
              RFC 3611, DOI 10.17487/RFC3611, November 2003,

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   [RFC4585]  Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
              "Extended RTP Profile for Real-time Transport Control
              Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
              DOI 10.17487/RFC4585, July 2006,

   [RFC4588]  Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R.
              Hakenberg, "RTP Retransmission Payload Format", RFC 4588,
              DOI 10.17487/RFC4588, July 2006,

   [RFC6679]  Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
              and K. Carlberg, "Explicit Congestion Notification (ECN)
              for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August
              2012, <>.

   [RFC7301]  Friedl, S., Popov, A., Langley, A., and E. Stephan,
              "Transport Layer Security (TLS) Application-Layer Protocol
              Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
              July 2014, <>.

   [RFC7667]  Westerlund, M. and S. Wenger, "RTP Topologies", RFC 7667,
              DOI 10.17487/RFC7667, November 2015,

   [RFC8085]  Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
              Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
              March 2017, <>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

   [RFC8298]  Johansson, I. and Z. Sarker, "Self-Clocked Rate Adaptation
              for Multimedia", RFC 8298, DOI 10.17487/RFC8298, December
              2017, <>.

   [RFC8698]  Zhu, X., Pan, R., Ramalho, M., and S. Mena, "Network-
              Assisted Dynamic Adaptation (NADA): A Unified Congestion
              Control Scheme for Real-Time Media", RFC 8698,
              DOI 10.17487/RFC8698, February 2020,

   [RFC8888]  Sarker, Z., Perkins, C., Singh, V., and M. Ramalho, "RTP
              Control Protocol (RTCP) Feedback for Congestion Control",
              RFC 8888, DOI 10.17487/RFC8888, January 2021,

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   [RFC8999]  Thomson, M., "Version-Independent Properties of QUIC",
              RFC 8999, DOI 10.17487/RFC8999, May 2021,

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,

   [RFC9001]  Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
              QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021,

   [RFC9002]  Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection
              and Congestion Control", RFC 9002, DOI 10.17487/RFC9002,
              May 2021, <>.

   [RFC9221]  Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
              Datagram Extension to QUIC", RFC 9221,
              DOI 10.17487/RFC9221, March 2022,

12.2.  Informative References

              Alvestrand, H. T., "RTCP message for Receiver Estimated
              Maximum Bitrate", Work in Progress, Internet-Draft, draft-
              alvestrand-rmcat-remb-03, 21 October 2013,

              Dawkins, S., "SDP Offer/Answer for RTP using QUIC as
              Transport", Work in Progress, Internet-Draft, draft-
              dawkins-avtcore-sdp-rtp-quic-00, 28 January 2022,

              Hurst, S., "QRT: QUIC RTP Tunnelling", Work in Progress,
              Internet-Draft, draft-hurst-quic-rtp-tunnelling-01, 28
              January 2021, <

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              Schinazi, D. and L. Pardue, "HTTP Datagrams and the
              Capsule Protocol", Work in Progress, Internet-Draft,
              draft-ietf-masque-h3-datagram-11, 17 June 2022,

              Murillo, S. G. and A. Gouaillard, "WebRTC-HTTP ingestion
              protocol (WHIP)", Work in Progress, Internet-Draft, draft-
              ietf-wish-whip-06, 29 December 2022,

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,

   [RFC3711]  Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
              Norrman, "The Secure Real-time Transport Protocol (SRTP)",
              RFC 3711, DOI 10.17487/RFC3711, March 2004,

   [RFC5761]  Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
              Control Packets on a Single Port", RFC 5761,
              DOI 10.17487/RFC5761, April 2010,

   [RFC6582]  Henderson, T., Floyd, S., Gurtov, A., and Y. Nishida, "The
              NewReno Modification to TCP's Fast Recovery Algorithm",
              RFC 6582, DOI 10.17487/RFC6582, April 2012,

   [RFC7826]  Schulzrinne, H., Rao, A., Lanphier, R., Westerlund, M.,
              and M. Stiemerling, Ed., "Real-Time Streaming Protocol
              Version 2.0", RFC 7826, DOI 10.17487/RFC7826, December
              2016, <>.

   [RFC8825]  Alvestrand, H., "Overview: Real-Time Protocols for
              Browser-Based Applications", RFC 8825,
              DOI 10.17487/RFC8825, January 2021,

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Internet-Draft                RTP over QUIC                February 2023

   [RFC8860]  Westerlund, M., Perkins, C., and J. Lennox, "Sending
              Multiple Types of Media in a Single RTP Session",
              RFC 8860, DOI 10.17487/RFC8860, January 2021,

   [RFC9308]  Kühlewind, M. and B. Trammell, "Applicability of the QUIC
              Transport Protocol", RFC 9308, DOI 10.17487/RFC9308,
              September 2022, <>.

Appendix A.  Experimental Results

   An experimental implementation of the mapping described in this
   document can be found on Github (
   over-quic).  The application implements the RTP over QUIC Datagrams
   mapping and implements SCReAM congestion control at the application
   layer.  It can optionally disable the builtin QUIC congestion control
   (NewReno).  The endpoints only use RTCP for congestion control
   feedback, which can optionally be disabled and replaced by the QUIC
   connection statistics as described in Section 6.1.

   Experimental results of the implementation can be found on Github
   (, too.


   Early versions of this document were similar in spirit to
   [I-D.draft-hurst-quic-rtp-tunnelling], although many details differ.
   The authors would like to thank Sam Hurst for providing his thoughts
   about how QUIC could be used to carry RTP.

   The authors would like to thank Bernard Aboba, David Schinazi, Lucas
   Pardue, Sergio Garcia Murillo, Spencer Dawkins, and Vidhi Goel for
   their valuable comments and suggestions contributing to this

Authors' Addresses

   Jörg Ott
   Technical University Munich

   Mathis Engelbart
   Technical University Munich

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