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IETF RFC 7850
Last modified on Saturday, April 30th, 2016
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Internet Engineering Task Force (IETF) S. Nandakumar
Request for Comments: 7850 Cisco Systems Inc
Category: Standards Track April 2016
ISSN: 2070-1721
Registering Values of the SDP 'proto' Field
for Transporting RTP Media over TCP under Various RTP Profiles
 Abstract
The Real-time Transport Protocol (RTP) specification establishes a
registry of profile names for use by higher-level control protocols,
such as the Session Description Protocol (SDP), to refer to the
transport methods. This specification describes the following new
SDP transport protocol identifiers for transporting RTP Media over
TCP: 'TCP/RTP/AVPF', 'TCP/RTP/SAVP', 'TCP/RTP/SAVPF',
'TCP/DTLS/RTP/SAVP', 'TCP/DTLS/RTP/SAVPF', 'TCP/TLS/RTP/AVP', and
'TCP/TLS/RTP/AVPF'.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 7850.
Copyright Notice
Copyright (c) 2016 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
(http://trustee.ietf.org/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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Nandakumar Standards Track PAGE 1 
RFC 7850 SDP 'proto' Registrations April 2016
Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol Identifiers . . . . . . . . . . . . . . . . . . . . 3
3.1. TCP/RTP/AVPF Transport Realization . . . . . . . . . . . 3
3.2. TCP/RTP/SAVP Transport Realization . . . . . . . . . . . 3
3.3. TCP/RTP/SAVPF Transport Realization . . . . . . . . . . . 3
3.4. TCP/DTLS/RTP/SAVP Transport Realization . . . . . . . . . 3
3.5. TCP/DTLS/RTP/SAVPF Transport Realization . . . . . . . . 4
3.6. TCP/TLS/RTP/AVP Transport Realization . . . . . . . . . . 4
3.7. TCP/TLS/RTP/AVPF Transport Realization . . . . . . . . . 4
4. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Overview
The Real-time Transport Protocol (RTP) provides end-to-end network
transport functions suitable for applications transmitting real-time
data such as audio or video over multicast or unicast network
services. The data transport is augmented by the RTP Control
Protocol (RTCP) to allow monitoring of the data delivery in a manner
scalable to large multicast networks and to provide minimal control
and identification functionality.
"SDP: Session Description Protocol" [RFC 4566] provides a general-
purpose format for describing multimedia sessions in announcements or
invitations. "TCP-Based Media Transport in the Session Description
Protocol (SDP)" [RFC 4145] specifies a general mechanism for
describing media transport over TCP using SDP with [RFC 4571] defining
a method for framing RTP and RTCP packets [RFC 3550] onto a
connection-oriented transport (such as TCP). "Connection-Oriented
Media Transport over the Transport Layer Security (TLS) Protocol in
the Session Description Protocol (SDP)" [RFC 4572] extends [RFC 4145]
for describing TCP-based media streams that are protected using TLS
[RFC 5246].
This specification describes additional SDP transport protocol
identifiers for transporting RTP media over TCP as defined in
Section 3.
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RFC 7850 SDP 'proto' Registrations April 2016
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC 2119].
3. Protocol Identifiers
The "m=" line in SDP specifies, among other items, the transport
protocol (identified via the "proto" field) to be used for the media
in the session. See Section 5.14 (Media Descriptions) of SDP
[RFC 4566] for a discussion on transport protocol identifiers.
The following is the format for an "m=" line, as specified in
[RFC 4566]:
m=<media> <port> <proto> <fmt> ...
3.1. TCP/RTP/AVPF Transport Realization
The TCP/RTP/AVPF transport describes RTP media with RTCP-based
feedback [RFC 4585] over TCP.
The RTP/AVPF stream over TCP is realized using the framing method
defined in [RFC 4571].
3.2. TCP/RTP/SAVP Transport Realization
The TCP/RTP/SAVP transport describes Secure RTP (SRTP) media
[RFC 3711] over TCP.
The RTP/SAVP stream over TCP is realized using the framing method
defined in [RFC 4571].
3.3. TCP/RTP/SAVPF Transport Realization
The TCP/RTP/SAVPF transport describes Secure RTP media with RTCP-
based feedback [RFC 5124] over TCP.
The RTP/SAVPF stream over TCP is realized using the framing method
defined in [RFC 4571].
3.4. TCP/DTLS/RTP/SAVP Transport Realization
The TCP/DTLS/RTP/SAVP transport describes Secure RTP media [RFC 3711]
using Datagram Transport Layer Security SRTP (DTLS-SRTP) [RFC 5764]
over TCP.
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RFC 7850 SDP 'proto' Registrations April 2016
RTP/SAVP using DTLS-based key establishment is realized according to
the procedures defined in [RFC 5764]. Also, the framing specified in
[RFC 4571] is used to transport DTLS-SRTP packets over TCP.
3.5. TCP/DTLS/RTP/SAVPF Transport Realization
The TCP/DTLS/RTP/SAVPF transport describes Secure RTP media with
RTCP-based feedback [RFC 5124] using DTLS-SRTP over TCP.
RTP/SAVPF using DTLS-based key establishment is realized according to
the procedures defined in [RFC 5764]. Also, the framing specified in
[RFC 4571] is used to transport DTLS-SRTP packets over TCP.
3.6. TCP/TLS/RTP/AVP Transport Realization
The TCP/TLS/RTP/AVP transport describes RTP Media on top of TLS over
TCP.
RTP/AVP packets are framed using the procedures from [RFC 4571] and
are transported as application data messages over the TLS association
setup using the procedures from [RFC 4572].
3.7. TCP/TLS/RTP/AVPF Transport Realization
The TCP/TLS/RTP/AVPF transport describes RTP media with RTCP-based
feedback [RFC 5124] on top of TLS over TCP.
RTP/AVPF packets are framed using the procedures from [RFC 4571] and
are transported as application data messages over the TLS association
setup using the procedures from [RFC 4572].
4. ICE Considerations
When procedures from [RFC 6544] are used to set up Interactive
Connectivity Establishment (ICE) [RFC 5245] candidates for a TCP
transport, the framing mechanism from [RFC 4571] MUST be used for
framing Session Traversal Utilities for NAT (STUN) packets (for
keepalives and consent checks), as defined in Section 3 of [RFC 6544].
5. IANA Considerations
This specification describes the following new SDP transport protocol
identifiers: 'TCP/RTP/AVPF', 'TCP/RTP/SAVP', 'TCP/RTP/SAVPF',
'TCP/DTLS/RTP/SAVP', 'TCP/DTLS/RTP/SAVPF', 'TCP/TLS/RTP/AVP', and
'TCP/TLS/RTP/AVPF', as defined in Section 3. These values have been
registered by the IANA under the "proto" subregistry in the "Session
Description Protocol (SDP) Parameters" registry.
Nandakumar Standards Track PAGE 4
RFC 7850 SDP 'proto' Registrations April 2016
+--------+---------------------+-----------+
| Type | SDP Name | Reference |
+--------+---------------------+-----------+
| proto | TCP/RTP/AVPF | RFC 7850 |
| | | |
| proto | TCP/RTP/SAVP | RFC 7850 |
| | | |
| proto | TCP/RTP/SAVPF | RFC 7850 |
| | | |
| proto | TCP/DTLS/RTP/SAVP | RFC 7850 |
| | | |
| proto | TCP/DTLS/RTP/SAVPF | RFC 7850 |
| | | |
| proto | TCP/TLS/RTP/AVP | RFC 7850 |
| | | |
| proto | TCP/TLS/RTP/AVPF | RFC 7850 |
+--------+---------------------+-----------+
6. Security Considerations
The new "proto" identifiers registered by this document in the SDP
parameters registry maintained by IANA are primarily for use by the
offer/answer model of the Session Description Protocol [RFC 3264] for
the negotiation and establishment of RTP-based media over the TCP
transport. This specification doesn't introduce any additional
security considerations beyond those specified by the individual
transport protocols identified in the "proto" identifiers and those
detailed in Section 7 of [RFC 4566].
7. References
7.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC 2119, March 1997,
<http://www.rfc-editor.org/info/RFC 2119>.
[RFC 4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC 4566,
July 2006, <http://www.rfc-editor.org/info/RFC 4566>.
[RFC 4571] Lazzaro, J., "Framing Real-time Transport Protocol (RTP)
and RTP Control Protocol (RTCP) Packets over Connection-
Oriented Transport", RFC 4571, DOI 10.17487/RFC 4571, July
2006, <http://www.rfc-editor.org/info/RFC 4571>.
Nandakumar Standards Track PAGE 5
RFC 7850 SDP 'proto' Registrations April 2016
[RFC 4572] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572,
DOI 10.17487/RFC 4572, July 2006,
<http://www.rfc-editor.org/info/RFC 4572>.
[RFC 5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245,
DOI 10.17487/RFC 5245, April 2010,
<http://www.rfc-editor.org/info/RFC 5245>.
[RFC 5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer
Security (DTLS) Extension to Establish Keys for the Secure
Real-time Transport Protocol (SRTP)", RFC 5764,
DOI 10.17487/RFC 5764, May 2010,
<http://www.rfc-editor.org/info/RFC 5764>.
[RFC 6544] Rosenberg, J., Keranen, A., Lowekamp, B., and A. Roach,
"TCP Candidates with Interactive Connectivity
Establishment (ICE)", RFC 6544, DOI 10.17487/RFC 6544,
March 2012, <http://www.rfc-editor.org/info/RFC 6544>.
7.2. Informative References
[RFC 3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC 3264, June 2002,
<http://www.rfc-editor.org/info/RFC 3264>.
[RFC 3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC 3550,
July 2003, <http://www.rfc-editor.org/info/RFC 3550>.
[RFC 3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, DOI 10.17487/RFC 3711, March 2004,
<http://www.rfc-editor.org/info/RFC 3711>.
[RFC 4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
the Session Description Protocol (SDP)", RFC 4145,
DOI 10.17487/RFC 4145, September 2005,
<http://www.rfc-editor.org/info/RFC 4145>.
Nandakumar Standards Track PAGE 6
RFC 7850 SDP 'proto' Registrations April 2016
[RFC 4585] 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/RFC 4585, July 2006,
<http://www.rfc-editor.org/info/RFC 4585>.
[RFC 5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for
Real-time Transport Control Protocol (RTCP)-Based Feedback
(RTP/SAVPF)", RFC 5124, DOI 10.17487/RFC 5124, February
2008, <http://www.rfc-editor.org/info/RFC 5124>.
[RFC 5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC 5246, August 2008,
<http://www.rfc-editor.org/info/RFC 5246>.
Acknowledgements
The author would like to thank Cullen Jennings, Alissa Cooper, Justin
Uberti, Mo Zanaty, Christer Holmberg, Jonathan Lennox, Flemming
Andreason, Roni Even, Ben Campbell, and Bo Burman for their reviews
and suggested improvements.
The author would also like to thank Adam Montville for the SecDir
review, Meral Shirazipour for the Gen-ART review, and Sarah Banks for
the OPS-Dir review.
Author's Address
Suhas Nandakumar
Cisco Systems Inc
707 Tasman Drive
San Jose, CA 95134
United States
Email: snandaku@cisco.com
Nandakumar Standards Track PAGE 7
RFC TOTAL SIZE: 15190 bytes
PUBLICATION DATE: Saturday, April 30th, 2016
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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