Port Mapping between Unicast and Multicast RTP Sessions
RFC 6284
Internet Engineering Task Force (IETF) A. Begen
Request for Comments: 6284 D. Wing
Category: Standards Track Cisco
ISSN: 2070-1721 T. Van Caenegem
Alcatel-Lucent
June 2011
Port Mapping between Unicast and Multicast RTP Sessions
Abstract
This document presents a port mapping solution that allows RTP
receivers to choose their own ports for an auxiliary unicast session
in RTP applications using both unicast and multicast services. The
solution provides protection against denial-of-service or packet
amplification attacks that could be used to cause one or more RTP
packets to be sent to a victim client.
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/rfc6284.
Copyright Notice
Copyright (c) 2011 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Begen, et al. Standards Track [Page 1]
RFC 6284 Port Mapping June 2011
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4
3. Token-Based Port Mapping . . . . . . . . . . . . . . . . . . . 5
3.1. Motivating Scenario . . . . . . . . . . . . . . . . . . . 6
3.2. Normative Behavior and Requirements . . . . . . . . . . . 9
4. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Port Mapping Request . . . . . . . . . . . . . . . . . . . 12
4.2. Port Mapping Response . . . . . . . . . . . . . . . . . . 13
4.3. Token Verification Request . . . . . . . . . . . . . . . . 15
4.3.1. Where to Include Token . . . . . . . . . . . . . . . . 16
4.4. Token Verification Failure . . . . . . . . . . . . . . . . 17
5. Procedures for Token Construction . . . . . . . . . . . . . . 18
6. Validating Tokens . . . . . . . . . . . . . . . . . . . . . . 20
7. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 21
7.1. The 'portmapping-req' Attribute . . . . . . . . . . . . . 21
7.1.1. ABNF Definition of 'portmapping-req' . . . . . . . . . 21
7.1.2. Offer/Answer Model Considerations . . . . . . . . . . 22
7.2. Requirements . . . . . . . . . . . . . . . . . . . . . . . 22
7.3. Example and Discussion . . . . . . . . . . . . . . . . . . 23
8. Address Pooling NATs . . . . . . . . . . . . . . . . . . . . . 24
9. Security Considerations . . . . . . . . . . . . . . . . . . . 24
9.1. Tokens . . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.2. The 'portmapping-req' Attribute . . . . . . . . . . . . . 26
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
10.1. Registration of SDP Attributes . . . . . . . . . . . . . . 26
10.2. Registration of RTCP Control Packet Types . . . . . . . . 27
10.3. SMT Values for TOKEN Packet Type Registry . . . . . . . . 27
10.4. RAMS Response Code Space Registry . . . . . . . . . . . . 27
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
12.1. Normative References . . . . . . . . . . . . . . . . . . . 28
12.2. Informative References . . . . . . . . . . . . . . . . . . 29
Begen, et al. Standards Track [Page 2]
RFC 6284 Port Mapping June 2011
1. Introduction
In (any-source or source-specific) multicast RTP applications,
destination ports (i.e., the ports on which the multicast receivers
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