Network Working Group H. T. Alvestrand
Internet-Draft Google
Intended status: Standards Track September 03, 2013
Expires: March 07, 2014

Transports for RTCWEB
draft-ietf-rtcweb-transports-01

Abstract

This document describes the data transport protocols used by RTCWEB, including the protocols used for interaction with intermediate boxes such as firewalls, relays and NAT boxes.

Requirements Language

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 [RFC2119].

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 http://datatracker.ietf.org/drafts/current/.

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This Internet-Draft will expire on March 07, 2014.

Copyright Notice

Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved.

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Table of Contents

1. Introduction

The IETF RTCWEB effort, part of the WebRTC effort carried out in cooperation between the IETF and the W3C, is aimed at specifying a protocol suite that is useful for real time multimedia exchange between browsers.

The overall effort is described in the RTCWEB overview document, [I-D.ietf-rtcweb-overview]. This document focuses on the data transport protocos that are used by conforming implementations.

This protocol suite is designed for WebRTC, and intends to satisfy the security considerations described in the WebRTC security documents, [I-D.ietf-rtcweb-security] and [I-D.ietf-rtcweb-security-arch].

2. Transport and Middlebox specification

2.1. System-provided interfaces

The protocol specifications used here assume that the following protocols are available to the implementations of the RTCWEB protocols:

[I-D.ietf-rtcweb-qos]. It does not assume that the DSCP codepoints will be honored, and does assume that they may be zeroed or changed, since this is a local configuration issue.

For both protocols, this specification assumes the ability to set the DSCP code point of the sockets opened on a per-packet basis, in order to achieve the prioritizations described in

If DSCP code points can only be set on a per-socket basis, not per-packet, one loses the ability to have the network discriminate reliably between classes of traffic sent over the same transport, but this does not prevent communication.

This specification does not assume that the implementation will have access to ICMP or raw IP.

2.2. Middle box related functions

The primary mechanism to deal with middle boxes is ICE, which is an appropriate way to deal with NAT boxes and firewalls that accept traffic from the inside, but only from the outside if it's in response to inside traffic (simple stateful firewalls).

In order to deal with situations where both parties are behind NATs which perform endpoint-dependent mapping (as defined in [RFC5128] section 2.4), TURN [RFC5766] MUST be supported.

In order to deal with firewalls that block all UDP traffic, TURN using TCP between the client and the server MUST be supported, and TURN using TLS between the client and the server MUST be supported.

ICE TCP candidates [RFC6062] MAY be supported; this may allow applications to achieve peer-to-peer communication across UDP-blocking firewalls, but this also requires use of the SRTP/AVPF/TCP profile of RTP.

The following specifications MUST be supported:

TURN over TLS over TCP MAY be supported. (QUESTION: SHOULD? MUST?)

For referring to STUN and TURN servers, this specification depends on the STUN URI, [I-D.nandakumar-rtcweb-stun-uri].

Further discussion of the interaction of RTCWEB with firewalls is contained in [I-D.hutton-rtcweb-nat-firewall-considerations]. This document makes no requirements on interacting with HTTP proxies or HTTP proxy configuration methods.

2.3. Transport protocols implemented

For data transport over the RTCWEB data channel [I-D.ietf-rtcweb-data-channel], RTCWEB implementations support SCTP over DTLS over ICE. This is specified in [I-D.ietf-tsvwg-sctp-dtls-encaps]. Negotiation of this transport in SCTP is defined in [I-D.ietf-mmusic-sctp-sdp].

The setup protocol for RTCWEB data channels is described in [I-D.jesup-rtcweb-data-protocol].

For transport of media, secure RTP is used. The details of the profile of RTP used are described in "RTP Usage" [I-D.ietf-rtcweb-rtp-usage].

RTCWEB implementations MUST support multiplexing of DTLS and RTP over the same port pair, as described in the DTLS_SRTP specification [RFC5764], section 5.1.2. Further separation of the DTLS traffic into SCTP and "other" is described in <need reference>.

3. IANA Considerations

This document makes no request of IANA.

Note to RFC Editor: this section may be removed on publication as an RFC.

4. Security Considerations

Security considerations are enumerated in [I-D.ietf-rtcweb-security].

5. Acknowledgements

This document is based on earlier versions embedded in [I-D.ietf-rtcweb-overview], which were the results of contributions from many RTCWEB WG members.

6. References

6.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocols", RFC 5245, April 2010.
[RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer Security (DTLS) Extension to Establish Keys for the Secure Real-time Transport Protocol (SRTP)", RFC 5764, May 2010.
[RFC5766] Mahy, R., Matthews, P. and J. Rosenberg, "Traversal Using Relays around NAT (TURN): Relay Extensions to Session Traversal Utilities for NAT (STUN)", RFC 5766, April 2010.
[RFC6062] Perreault, S. and J. Rosenberg, "Traversal Using Relays around NAT (TURN) Extensions for TCP Allocations", RFC 6062, November 2010.
[I-D.ietf-rtcweb-security] Rescorla, E., "Security Considerations for RTC-Web", Internet-Draft draft-ietf-rtcweb-security-04, January 2013.
[I-D.ietf-rtcweb-rtp-usage] Perkins, C., Westerlund, M. and J. Ott, "Web Real-Time Communication (WebRTC): Media Transport and Use of RTP", Internet-Draft draft-ietf-rtcweb-rtp-usage-05, October 2012.
[I-D.ietf-rtcweb-data-channel] Jesup, R., Loreto, S. and M. Tuexen, "RTCWeb Datagram Connection", Internet-Draft draft-ietf-rtcweb-data-channel-02, October 2012.
[I-D.ietf-rtcweb-security-arch] Rescorla, E., "RTCWEB Security Architecture", Internet-Draft draft-ietf-rtcweb-security-arch-06, January 2013.
[I-D.ietf-rtcweb-qos] Dhesikan, S., Druta, D., Jones, P. and J. Polk, "DSCP and other packet markings for RTCWeb QoS", Internet-Draft draft-ietf-rtcweb-qos-00, October 2012.
[I-D.ietf-tsvwg-sctp-dtls-encaps] Jesup, R., Loreto, S., Stewart, R. and M. Tuexen, "DTLS Encapsulation of SCTP Packets for RTCWEB", Internet-Draft draft-ietf-tsvwg-sctp-dtls-encaps-00, February 2013.
[I-D.ietf-mmusic-sctp-sdp] Loreto, S. and G. Camarillo, "Stream Control Transmission Protocol (SCTP)-Based Media Transport in the Session Description Protocol (SDP)", Internet-Draft draft-ietf-mmusic-sctp-sdp-03, January 2013.
[I-D.nandakumar-rtcweb-stun-uri] Nandakumar, S., Salgueiro, G., Jones, P. and M. Petit-Huguenin, "URI Scheme for Session Traversal Utilities for NAT (STUN) Protocol", Internet-Draft draft-nandakumar-rtcweb-stun-uri-03, January 2013.

6.2. Informative References

[RFC5128] Srisuresh, P., Ford, B. and D. Kegel, "State of Peer-to-Peer (P2P) Communication across Network Address Translators (NATs)", RFC 5128, March 2008.
[I-D.ietf-rtcweb-overview] Alvestrand, H., "Overview: Real Time Protocols for Brower-based Applications", Internet-Draft draft-ietf-rtcweb-overview-06, February 2013.
[I-D.jesup-rtcweb-data-protocol] Jesup, R., Loreto, S. and M. Tuexen, "WebRTC Data Channel Protocol", Internet-Draft draft-jesup-rtcweb-data-protocol-03, September 2012.
[I-D.hutton-rtcweb-nat-firewall-considerations] Stach, T., Hutton, A. and J. Uberti, "RTCWEB Considerations for NATs, Firewalls and HTTP proxies", Internet-Draft draft-hutton-rtcweb-nat-firewall-considerations-00, March 2013.

Appendix A. Change log

A.1. Changes from -00 to -01

Author's Address

Harald Alvestrand Google EMail: harald@alvestrand.no