RTP Payload Format for the SCIP Codec
draft-scip-payload-00

Document Type Active Internet-Draft (individual)
Authors Daniel Hanson  , MikeFaller  , Keith Maver 
Last updated 2021-04-16
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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 
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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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