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Versions: 00                                                            
      Payload Working Group                                    D. Hanson
      Internet Draft                                           M. Faller
      Intended status: Standards Track                          K. Maver
      Expires: October 18, 2021         General Dynamics Mission Systems
                                                          April 16, 2021
      
      
      
                      RTP Payload Format for the SCIP Codec
                          draft-scip-payload-00.txt
      
      
      
      Status of this Memo
      
         Copyright (c) 2021 IETF Trust and the persons identified as the
         document authors.  All rights reserved.
      
         This Internet-Draft is submitted in full conformance with the
         provisions of BCP 78 and BCP 79.
      
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         Internet-Drafts are working documents of the Internet
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         http://datatracker.ietf.org/drafts/current/.
      
         Internet-Drafts are draft documents valid for a maximum of six
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         This Internet-Draft will expire on October 18, 2021.
      
      Abstract
      
         This document describes the RTP payload format of the Secure
         Communication Interoperability Protocol (SCIP) as audio and
         video media subtypes.  It provides RFC 6838 compliant media
      
      
      
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         subtype definitions.  SCIP-214.2 and SCIP-210 describe the
         protocols that comprise the SCIP RTP packet payload.  This
         document follows the registration for related media types
         called "audio/scip" and "video/scip" with IANA and formatted
         according to RFC 4855.
      
      Table of Contents
      
         1. Introduction..............................................2
            1.1. Conventions..........................................2
            1.2. Abbreviations........................................3
         2. Background................................................3
         3. Media Format Description..................................4
         4. Payload Format............................................5
            4.1. RTP Header Fields....................................5
         5. Payload Format Parameters.................................5
            5.1. Media Subtype "audio/scip"...........................6
            5.2. Media Subtype "video/scip"...........................7
            5.3. Mapping to SDP.......................................8
            5.4. SDP Offer/Answer Considerations......................9
         6. Security Considerations...................................9
         7. IANA Considerations.......................................9
         8. References................................................9
            8.1. Normative References.................................9
            8.2. Informative References..............................11
         9. Authors' Addresses.......................................12
      
      1. Introduction
      
         The IANA registration of media subtype types in the IETF tree
         created two similar media subtypes "scip" under the audio and
         video media types [AUDIOSCIP], [VIDEOSCIP].  This document, as
         the common top-level reference, provides information on their
         similarities and differences and the usage of those media
         subtypes.
      
         This document details usage of the scip pseudo-codec as a
         secure session establishment protocol and transport protocol
         over RTP. It provides a reference for network security
         policymakers, network equipment OEMs, procurement personnel,
         and government agency and commercial industry representatives.
      
      1.1. Conventions
      
         The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
         NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
      
      
      
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         "OPTIONAL" in this document are to be interpreted as described
         in [RFC2119].
      
         Best current practices for writing an RTP payload format
         specification were followed [RFC2736] [RFC8088].
      
      1.2. Abbreviations
      
         The following abbreviations are used in this document.
      
           AVP:      Audio/Video Profile
           DTX:      Discontinuous Transmission
           FNBDT:    Future Narrowband Digital Terminal
           ICWG:     Interoperability Control Working Group
           IICWG:    International Interoperability Control Working
         Group
           NATO:     North Atlantic Treaty Organization
           SCIP:     Secure Communication Interoperability Protocol
           SDP:      Session Description Protocol
      
      2. Background
      
         The Secure Communication Interoperability Protocol (SCIP)
         allows the negotiation of several voice, data, and video
         applications using various encryption suites.  SCIP also
         provides several important characteristics that have led to its
         broad acceptance in the international user community.  These
         features include end-to-end security at the application layer,
         authentication of user identity, the ability to apply different
         security levels for each secure session, and secure
         communication over any end-to-end data connection.
      
         SCIP began in the U.S. as the FNBDT (Future Narrowband Digital
         Terminal) Protocol.  A combined Department of Defense and
         vendor consortium formed a governing organization named the
         ICWG (Interoperability Control Working Group).  In time, the
         group expanded to include NATO, NATO partners and European
         vendors under the name IICWG (International Interoperability
         Control Working Group), which was later renamed the SCIP
         Working Group.
      
         SCIP is presently implemented in U.S. and NATO secure voice,
         video, and data products operating on commercial, private, and
         tactical IP networks worldwide using the scip media subtype.
         First generation SCIP devices operated on circuit-switched
      
      
      
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         networks.  SCIP was then expanded to radio and IP networks.
         The scip media subtype transports SCIP secure session
         establishment signaling and secure application traffic.  The
         built-in negotiation and flexibility provided by the SCIP
         standards make it a natural choice for many scenarios that
         require various secure applications and associated encryption
         suites.  SCIP has been endorsed by many nations as the secure
         end-to-end solution for secure voice, video, and data devices.
         SCIP standards are currently available to participating
         government/military communities and select OEMs of equipment
         that support SCIP.
      
         However, SCIP must operate over global networks (including
         private and commercial networks).  Without access to necessary
         information to support SCIP, some networks may not support the
         SCIP media subtypes. Issues may occur simply because
         information is not as readily available to OEMs, network
         administrators, and network architects.
      
         This RFC provides essential information about audio/scip and
         video/scip media subtypes that enables network equipment
         manufacturers to include scip as a known audio and video media
         subtype in their equipment and enables network administrators
         to define and implement a compatible security policy.
      
         All current IP-based SCIP devices support "scip" as a media
         subtype. Registration of scip as a media subtype provides a
         common reference for network equipment manufacturers to
         recognize SCIP in a payload declaration.
      
      3. Media Format Description
      
         The "scip" media subtype indicates support for and identifies
         SCIP traffic that is being transferred using RTP.  SCIP traffic
         requires end-to-end bit integrity, therefore transcoding SHALL
         NOT be performed over the end-to-end IP connection.  The
         audio/scip and video/scip media subtype data streams within the
         network, including the VoIP network, MUST be a transparent
         relay and be treated as "clear-channel data", similar to the
         Clearmode media subtype defined by RFC 4040.  However,
         Clearmode is defined as a gateway protocol and limited to a
         sample rate of 8000 Hz and 64kbps bandwidth only [RFC4040].
         Clearmode is not defined for the higher sample and data rates
         required for some SCIP traffic.
      
      
      
      
      
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      4. Payload Format
      
         The RTP Packet content of SCIP traffic is dependent upon the
         SCIP session state.  SCIP secure session establishment uses
         protocols defined in SCIP-210 [SCIP210] to negotiate an
         application.  SCIP secure traffic may consist of the encrypted
         output of codecs such as MELPe [RFC8130], G.729D [RFC3551],
         H.264 [RFC6184], or other media encodings, based on the
         application negotiated during SCIP secure session
         establishment.  SCIP traffic is highly variable and may include
         other SCIP signaling information in the media stream.  SCIP
         traffic may not always be a continuous stream at the bit rate
         specified in the SDP [RFC8866] since discontinuous transmission
         (DTX) or other mechanisms may be used.  The SCIP payload size
         will vary, especially during SCIP secure session establishment.
      
      4.1. RTP Header Fields
      
         The RTP header fields SHOULD conform to RFC 3550.  This is a
         SHOULD rather than a SHALL in recognition that legacy SCIP-
         enabled products may not strictly adhere to RFC 3550.
      
         SCIP traffic may be continuous or discontinuous.  The Timestamp
         field increments based on the sampling clock for discontinuous
         transmission as described in [RFC3550], Section 5.1.  The
         Timestamp field for continuous transmission applications is
         dependent on the sampling rate of the media as specified in the
         media subtype's specification (e.g., MELPe [RFC8130]).  Note
         that during a call, both discontinuous and continuous traffic
         is highly probable.  Therefore, a jitter buffer MAY be
         implemented in endpoint devices only but SHOULD NOT be
         implemented in network devices.
      
         The Marker bit SHOULD be set to zero for discontinuous traffic.
         The Marker bit for continuous traffic is based on the
         underlying media subtype specification.  This specification is
         a SHOULD rather than a SHALL in recognition that legacy SCIP-
         enabled products may not strictly adhere to the media subtype
         specification.
      
      5. Payload Format Parameters
      
         The SCIP RTP payload format is identified using the scip media
         subtype, which is registered in accordance with [RFC4855] and
         per the media type registration template form [RFC6838].  A
         clock rate of 8000 Hz SHALL be used for "audio/scip".  A clock
         rate of 90000 Hz SHALL be used for "video/scip".
      
      
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      5.1. Media Subtype "audio/scip"
      
         Media type name: audio
      
         Media subtype name: scip
      
         Required parameters: N/A
      
         Optional parameters: N/A
      
         Encoding considerations: Binary.  This media subtype is only
         defined for transfer via RTP.  There SHALL be no
         encoding/decoding (transcoding) of the audio stream as it
         traverses the network.
      
         Security considerations: See Section 6.
      
         Interoperability considerations: N/A
      
         Published specifications: [SCIP214], [SCIP210]
      
         Applications which use this media: N/A
      
         Fragment Identifier considerations: none
      
         Restrictions on usage: N/A
      
         Additional information:
      
            1. Deprecated alias names for this type: N/A
      
            2. Magic number(s): N/A
      
            3. File extension(s): N/A
      
            4. Macintosh file type code: N/A
      
            5. Object Identifiers: N/A
      
         Person to contact for further information:
      
            1. Name: Michael Faller and Daniel Hanson
      
            2. Email: michael.faller@gd-ms.com and dan.hanson@gd-ms.com
      
         Intended usage: Common, Government and Military
      
      
      
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         Authors:
      
            Michael Faller - michael.faller@gd-ms.com
      
            Daniel Hanson - dan.hanson@gd-ms.com
      
         Change controller:
      
            SCIP Working Group - ncia.cis3@ncia.nato.int
      
      5.2. Media Subtype "video/scip"
      
         Media type name: video
      
         Media subtype name: scip
      
         Required parameters: N/A
      
         Optional parameters: N/A
      
         Encoding considerations: Binary.  This media subtype is only
         defined for transfer via RTP.  There SHALL be no
         encoding/decoding (transcoding) of the video stream as it
         traverses the network.
      
         Security considerations: See Section 6.
      
         Interoperability considerations: N/A
      
         Published specifications: [SCIP214], [SCIP210]
      
         Applications which use this media: N/A
      
         Fragment Identifier considerations: none
      
         Restrictions on usage: N/A
      
         Additional information:
      
            1. Deprecated alias names for this type: N/A
      
            2. Magic number(s): N/A
      
            3. File extension(s): N/A
      
            4. Macintosh file type code: N/A
      
      
      
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            5. Object Identifiers: N/A
      
         Person to contact for further information:
      
            1. Name: Michael Faller and Daniel Hanson
      
            2. Email: michael.faller@gd-ms.com and dan.hanson@gd-ms.com
      
         Intended usage: Common, Government and Military
      
         Authors:
      
            Michael Faller - michael.faller@gd-ms.com
      
            Daniel Hanson - dan.hanson@gd-ms.com
      
         Change controller:
      
            SCIP Working Group - ncia.cis3@ncia.nato.int
      
      5.3. Mapping to SDP
      
         The mapping of the above defined payload format media subtype
         and its parameters SHALL be done according to Section 3 of
         [RFC4855].
      
         An example mapping for audio/scip is:
      
            m=audio 50000 RTP/AVP 96
            a=rtpmap:96 scip/8000
      
         An example mapping for video/scip is:
      
            m=video 50002 RTP/AVP 97
            a=rtpmap:97 scip/90000
      
         An example mapping for both audio/scip and video/scip is:
      
            m=audio 50000 RTP/AVP 96
            a=rtpmap:96 scip/8000
            m=video 50002 RTP/AVP 97
            a=rtpmap:97 scip/90000
      
         The application negotiation between endpoints will determine
         whether the audio and video streams are transported as separate
      
      
      
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         streams over the audio and video payload types or as a single
         media stream on the video payload type.
      
      5.4. SDP Offer/Answer Considerations
      
         In accordance with the SDP Offer/Answer model [RFC3264], the
         SCIP device SHALL list the SCIP payload type in order of
         preference in the "m" media line.
      
      6. Security Considerations
      
         RTP packets using the payload format defined in this
         specification are subject to the security considerations
         discussed in the RTP specification [RFC3550], and in any
         applicable RTP profile such as RTP/AVP [RFC3551], RTP/AVPF
         [RFC4585], RTP/SAVP [RFC3711], or RTP/ SAVPF [RFC5124].
         However, as "Securing the RTP Protocol Framework: Why RTP Does
         Not Mandate a Single Media Security Solution" [RFC7202]
         discusses, it is not an RTP payload format's responsibility to
         discuss or mandate what solutions are used to meet the basic
         security goals like confidentiality, integrity, and source
         authenticity for RTP in general.  This responsibility lays on
         anyone using RTP in an application.  They can find guidance on
         available security mechanisms and important considerations in
         "Options for Securing RTP Sessions" [RFC7201].  Applications
         SHOULD use one or more appropriate strong security mechanisms.
         The rest of this Security Considerations section discusses the
         security impacting properties of the payload format itself.
      
         This RTP payload format and its media decoder do not exhibit
         any significant non-uniformity in the receiver-side
         computational complexity for packet processing, and thus are
         unlikely to pose a denial-of-service threat due to the receipt
         of pathological data.  Nor does the RTP payload format contain
         any active content.
      
      7. IANA Considerations
      
         The audio/scip and video/scip media subtypes have been
         registered with IANA [AUDIOSCIP] [VIDEOSCIP].
      
      8. References
      
      8.1. Normative References
      
         [AUDIOSCIP] Faller, M., and D. Hanson, "audio/scip", Internet
                     Assigned Numbers Authority (IANA), 28 January 2021,
      
      
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                     <https://www.iana.org/assignments/media-
                     types/audio/scip>.
      
         [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
                     Requirement Levels", BCP 14, RFC 2119, DOI
                     10.17487/RFC2119, March 1997, <https://www.rfc-
                     editor.org/info/rfc2119>.
      
         [RFC2736]   Handley, M. and C. Perkins, "Guidelines for Writers
                     of RTP Payload Format Specifications", BCP 36, RFC
                     2736, DOI 10.17487/RFC2736, December 1999,
                     <https://www.rfc-editor.org/info/rfc2736>.
      
         [RFC3264]   Rosenberg, J., and H. Schulzrinne, "An Offer/Answer
                     Model with Session Description Protocol (SDP)", RFC
                     3264, June 2002, <https://www.rfc-
                     editor.org/info/rfc3264>.
      
         [RFC3550]   Schulzrinne, H., Casner, S., Frederick, R., and V.
                     Jacobson, "RTP: A Transport Protocol for Real-Time
                     Applications", STD 64, RFC 3550, July 2003,
                     <https://www.rfc-editor.org/info/rfc3550>.
      
         [RFC3551]  Schulzrinne, H., and S. Casner, "RTP Profile for
                     Audio and Video Conferences with Minimal Control",
                     RFC 3551, July 2003, <https://www.rfc-
                     editor.org/info/rfc3551>.
      
         [RFC3711]  Baugher, M., McGrew, D., Naslund M., Carrara, E.,
                     and K. Norrman, "The Secure Real-time Transport
                     Protocol (SRTP)", RFC 3711, March 2004,
                     <https://www.rfc-editor.org/info/rfc3711>.
      
         [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, <https://www.rfc-editor.org/info/rfc4585>.
      
         [RFC5124]   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/RFC5124, February 2008, <https://www.rfc-
                     editor.org/info/rfc5124>.
      
         [RFC8866]   Begen, A., Kyzivat P., Perkins C., and M. Handley,
                     "SDP: Session Description Protocol", RFC 8866,
      
      
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                     January 2021, <https://www.rfc-
                     editor.org/info/rfc8866>.
      
         [SCIP210]   SCIP-210, "SCIP Signaling Plan", Revision 3.10, 26
                     October 2017, request access via email
                     <ncia.cis3@ncia.nato.int>.
      
         [SCIP214]   SCIP-214.2, "Secure Communication Interoperability
                     Protocol (SCIP) over Real-time Transport Protocol
                     (RTP)", Revision 1.1, 18 April 2014, request access
                     via email <ncia.cis3@ncia.nato.int>.
      
         [VIDEOSCIP] Faller, M., and D. Hanson, "video/scip", Internet
                     Assigned Numbers Authority (IANA), 28 January 2021,
                     <https://www.iana.org/assignments/media-
                     types/video/scip>.
      
      8.2. Informative References
      
         [RFC4040]   Kreuter, R., "RTP Payload Format for a 64 kbit/s
                     Transparent Call", RFC 4040, April 2005,
                     <https://www.rfc-editor.org/info/rfc4040>.
      
         [RFC4855]   Casner, S., "Media Type Registration of RTP Payload
                     Formats", RFC 4855, February 2007,
                     <https://www.rfc-editor.org/info/rfc4855>.
      
         [RFC6184]   Wang, Y., Even, R., et al. "RTP Payload Format for
                     H.264 Video", RFC 6184, May 2011, <https://www.rfc-
                     editor.org/info/rfc6184>.
      
         [RFC6838]   Freed, N., Klensin, J., and T. Hansen, "Media Type
                     Specifications and Registration Procedures", BCP
                     13, RFC 6838, January 2013, <https://www.rfc-
                     editor.org/info/rfc6838>.
      
         [RFC7201]   Westerlund, M. and C. Perkins, "Options for
                     Securing RTP Sessions", RFC 7201, DOI
                     10.17487/RFC7201, April 2014, <https://www.rfc-
                     editor.org/info/rfc7201>.
      
         [RFC7202]   Perkins, C. and M. Westerlund, "Securing the RTP
                     Framework: Why RTP Does Not Mandate a Single Media
                     Security Solution", RFC 7202, DOI 10.17487/RFC7202,
                     April 2014, <https://www.rfc-
                     editor.org/info/rfc7202>.
      
      
      
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         [RFC8088]   Westerlund, M. "How to Write an RTP Payload
                     Format", RFC 8088, May 2017, <http://www.rfc-
                     editor.org/info/rfc8088>.
      
         [RFC8130]   Demjanenko, V., and D. Satterlee, "RTP Payload
                     Format for MELPe Codec", RFC 8130, March 2017,
                     <https://www.rfc-editor.org/info/rfc8130>.
      
      9. Authors' Addresses
      
         Daniel Hanson
         General Dynamics Mission Systems, Inc.
         150 Rustcraft Road
         Dedham, MA 02026, USA
         E-mail: dan.hanson@gd-ms.com
      
         Michael Faller
         General Dynamics Mission Systems, Inc.
         150 Rustcraft Road
         Dedham, MA 02026, USA
         E-mail: michael.faller@gd-ms.com
      
         Keith Maver
         General Dynamics Mission Systems, Inc.
         150 Rustcraft Road
         Dedham, MA 02026, USA
         E-mail: keith.maver@gd-ms.com
      
         SCIP Working Group, CIS3 Partnership
         NATO Communications and Information Agency
         Oude Waalsdorperweg 61, 2597AK
         The Hague, The Netherlands
         E-mail: ncia.cis3@ncia.nato.int
      
      
      
      
      
      
      
      
      
      
      
      
      
      
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