Securing the RTP Framework: Why RTP Does Not Mandate a Single Media Security Solution
RFC 7202

Internet Engineering Task Force (IETF)                        C. Perkins
Request for Comments: 7202                         University of Glasgow
Category: Informational                                    M. Westerlund
ISSN: 2070-1721                                                 Ericsson
                                                              April 2014

                      Securing the RTP Framework:
       Why RTP Does Not Mandate a Single Media Security Solution

Abstract

   This memo discusses the problem of securing real-time multimedia
   sessions.  It also explains why the Real-time Transport Protocol
   (RTP) and the associated RTP Control Protocol (RTCP) do not mandate a
   single media security mechanism.  This is relevant for designers and
   reviewers of future RTP extensions to ensure that appropriate
   security mechanisms are mandated and that any such mechanisms are
   specified in a manner that conforms with the RTP architecture.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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/rfc7202.

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Copyright Notice

   Copyright (c) 2014 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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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  RTP Applications and Deployment Scenarios . . . . . . . . . .   3
   3.  RTP Media Security  . . . . . . . . . . . . . . . . . . . . .   4
   4.  RTP Session Establishment and Key Management  . . . . . . . .   5
   5.  On the Requirement for Strong Security in Framework Protocols   5
   6.  Securing the RTP Framework  . . . . . . . . . . . . . . . . .   6
   7.  Conclusions . . . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   10. Informative References  . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The Real-time Transport Protocol (RTP) [RFC3550] is widely used for
   voice over IP, Internet television, video conferencing, and other
   real-time and streaming media applications.  Despite this use, the
   basic RTP specification provides only limited options for media
   security and defines no standard key exchange mechanism.  Rather, a
   number of extensions are defined that can provide confidentiality and
   authentication of RTP media streams and RTP Control Protocol (RTCP)
   messages.  Other mechanisms define key exchange protocols.  This memo
   outlines why it is appropriate that multiple extension mechanisms are
   defined rather than mandating a single security and keying mechanism
   for all users of RTP.

   The IETF policy "Strong Security Requirements for Internet
   Engineering Task Force Standard Protocols" [RFC3365] (the so-called
   "Danvers Doctrine") states that "we MUST implement strong security in
   all protocols to provide for the all too frequent day when the
   protocol comes into widespread use in the global Internet".  The
   security mechanisms defined for use with RTP allow these requirements

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   to be met.  However, since RTP is a protocol framework that is
   suitable for a wide variety of use cases, there is no single security
   mechanism that is suitable for every scenario.  This memo outlines