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Versions: (draft-df-stecker-expertenforum-payload-tetra) 00

payload                                                      Reisenbauer
Internet-Draft                                                Frequentis
Intended status: Standards Track                              Brandhuber
Expires: October 24, 2018                                       eurofunk
                                                                Hagedorn
                                                                Hagedorn
                                                                Hoehnsch
                                                               T-Systems
                                                                    Wenk
                                                              Frequentis
                                                          April 22, 2018


              RTP Payload Format for the TETRA Audio Codec
                      draft-ietf-payload-tetra-00

Abstract

   This document specifies a Real-time Transport Protocol (RTP) payload
   format for TETRA encoded speech signals.  The payload format is
   designed to be able to interoperate with existing TETRA transport
   formats on non-IP networks.  A media type registration is included,
   specifying the use of the RTP payload format and the storage format.

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

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 24, 2018.

Copyright Notice

   Copyright (c) 2018 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
   Provisions Relating to IETF Documents



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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used In This Document . . . . . . . . . . . . . .   3
   3.  Media Format Background . . . . . . . . . . . . . . . . . . .   3
   4.  Payload format  . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  RTP Header Usage  . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Payload layout  . . . . . . . . . . . . . . . . . . . . .   4
     4.3.  Payload Header  . . . . . . . . . . . . . . . . . . . . .   5
       4.3.1.  I bit: Frame Indicator  . . . . . . . . . . . . . . .   5
       4.3.2.  F bit: Frame Type . . . . . . . . . . . . . . . . . .   5
       4.3.3.  CTRL: Control bit(5 bits) . . . . . . . . . . . . . .   5
       4.3.4.  C bit: Failed Crypto operation indication . . . . . .   6
       4.3.5.  FRAME_NR: FN (5 bits) . . . . . . . . . . . . . . . .   6
       4.3.6.  R: Audio Signal Relevance (3 bits)  . . . . . . . . .   6
       4.3.7.  S: Spare (7 bits) . . . . . . . . . . . . . . . . . .   7
     4.4.  Payload Data  . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Payload example . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Congestion Control Considerations . . . . . . . . . . . . . .   8
   7.  Payload Format Parameters . . . . . . . . . . . . . . . . . .   8
     7.1.  Media Type Definition . . . . . . . . . . . . . . . . . .   8
   8.  Mapping to SDP  . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Offer/Answer Considerations . . . . . . . . . . . . . . .  10
     8.2.  Declarative SDP Considerations  . . . . . . . . . . . . .  10
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  11
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     11.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   This document specifies the payload format for packetization of
   TErrestial Trunked Radio (TETRA) encoded speech signals
   [ETSI-TETRA-Codec] into the Real-time Transport Protocol (RTP)
   [RFC3550].  The payload format supports transmission of multiple
   channels, multiple frames per payload, robustness against packet
   loss, and interoperation with existing TETRA transport formats on
   non-IP networks, as described in Section Section 3.



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   The payload format itself is specified in Section Section 4.

2.  Conventions Used In This Document

   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 [RFC2119] when they
   appear in ALL CAPS.  These words may also appear in this document in
   lower case as plain English words, absent their normative meanings.

   The following acronyms are used in this document:

   o  ETSI: European Telecommunications Standards Institute
   o  TETRA: TErrestial Trunked Radio

   The byte order used in this document is network byte order, i.e., the
   most significant byte first.  The bit order is also the most
   significant bit first.  This is presented in all figures as having
   the most significant bit leftmost on a line and with the lowest
   number.  Some bit fields may wrap over multiple lines in which cases
   the bits on the first line are more significant than the bits on the
   next line.

   Best current practices for writing an RTP payload format
   specification were followed [RFC2736] updated with [RFC8088].

3.  Media Format Background

   The TETRA codec is used as vocoder for TETRA systems.  The TETRA
   codec is designed for compressing 30ms of audio speech data into 137
   bits.  The TETRA codec is designed in such a way that on the air
   interface two of theses 30ms samples are transported together (sub-
   block 1 and sub-block 2).  The codec allows that data of the first
   30ms voice frame can be stolen and used for other purposes, e.g. for
   the exchange of dynamically updated key-material in end-to-end
   encrypted voice sessions.  Codec payload serialisation within the
   traditional circuit mode based TETRA system is specified for TDM
   lines with 2048 kBit/s.  For this purpose two optional formats are
   defined [ETSI-TETRA-Codec], the first format is called FSTE (First
   Speech Transport Encoding Format), the other format is called OSTE
   (Optimized Speech Transport Encoding Format).  These two formats
   defer mainly insofar that the OSTE format transports an additional 5
   bit frame number, which provides timing information from the air
   interface to the receiving side in order to save the need for
   buffering due to different transports speed on air and in 64 kbit/s
   circuit switched networks.  The RTP payload format is defined such
   that the value of this frame number can be transported.




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4.  Payload format

   The RTP payload format is designed in such a way that it can carry
   the information needed to map the FSTE and OSTE format from
   [ETSI-TETRA-ISI].  The RTP format is defined such that both of the
   independent sub-blocks can be transferred separately or together
   within one RTP packet.  Both of them contain the same information in
   terms of control bits - the information is propagated redundantly.
   This redundancy is driven by on one hand to simplify the encoding
   process in direction from E1 to RTP on the other to provide the
   option to go for either 30ms or 60ms packet size.  The redundant
   information SHALL be propagated consistently equal - otherwise the
   behavior of the receiver is unspecified.  The payload format is
   chosen such that the TETRA data bits are octet aligned.

4.1.  RTP Header Usage

   The format of the RTP header is specified in [RFC3550].  The use of
   the fields of the RTP header by the TETRA payload format is
   consistent with that specification.

   The payload length of TETRA is an integer number of octets;
   therefore, no padding is necessary.

   The timestamp, sequence number, and marker bit (M) of the RTP header
   are used in accordance with Section 4.1 of [RFC3551].

   The RTP payload type for Tetra is to be assigned dynamically.

4.2.  Payload layout

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |I|F|  CTRL   |C|FRAME_NR |  R  |D(1)                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                           D(137)|  S          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+







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4.3.  Payload Header

4.3.1.  I bit: Frame Indicator

   1: The following frame contains a first block of two sub-blocks

   0: The following frame contains a separated sub-block.  A sub-block
   marked as such could either be a second sub-block, or an independent
   block, which does not have a relation with any first block.  To
   distinguish between the one and the other the information of the
   Control bits has to be evaluated.

4.3.2.  F bit: Frame Type

                       +-------+-------------------+
                       | Value |   Frame contains  |
                       +-------+-------------------+
                       |   0   | FSTE encoded data |
                       |   1   | OSTE encoded data |
                       +-------+-------------------+

4.3.3.  CTRL: Control bit(5 bits)

   Ctrl 1..3 according table 2 of [ETSI-TETRA-ISI].

                  +-------+---------------+-------------+
                  | Value |  Sub block 1  | Sub block 2 |
                  +-------+---------------+-------------+
                  |  000  |     normal    |    normal   |
                  |  001  |    C stolen   |    normal   |
                  |  010  |    U stolen   |    normal   |
                  |  011  |    C stolen   |   C stolen  |
                  |  100  |    C stolen   |   U stolen  |
                  |  101  |    U stolen   |   C stolen  |
                  |  110  |    U stolen   |   U stolen  |
                  |  111  | O&M ISI block |             |
                  +-------+---------------+-------------+

   Ctrl 4..5 according table 3 of [ETSI-TETRA-ISI].

             +-------+-------------------+-------------------+
             | Value |    Sub block 1    |    Sub block 2    |
             +-------+-------------------+-------------------+
             |   00  |   BFI no errors   |   BFI no errors   |
             |   01  |   BFI no errors   | BFI with error(s) |
             |   10  | BFI with error(s) |  BFI no error(s)  |
             |   11  | BFI with error(s) | BFI with error(s) |
             +-------+-------------------+-------------------+



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   NOTE: The meaning of C4 and C5 is outside the scope of the present

4.3.4.  C bit: Failed Crypto operation indication

   This bit may be set to "1" if a decryption (encrypted audio along the
   circuit switched mobile network, decryption at the RTP sender
   forwarding this audio) operation could not be performed successfully
   for the specific half-block.  Consequently, the encryption status of
   the half-block audio data is unknown.  Implementation of an RTP
   receiver has to take into account "C bit" when forwarding such TETRA
   audio data (either to a decoder directly or via TETRA infrastructure
   to a TETRA mobile unit), the contained audio might be scrambled -
   depending if the audio originally was generated as a plain-override
   half-block or as an encrypted half-block.

4.3.5.  FRAME_NR: FN (5 bits)

   Those bits contain an uplink frame number as defined in table 8 of
   [ETSI-TETRA-ISI].  If no frame number is available the FRAME_NR value
   SHALL be set to 00000.

4.3.6.  R: Audio Signal Relevance (3 bits)

   The Audio Signal Relevance bits contain information about the
   Relevance of the voice packet contained here.

   R 1

   0: no audio signal relevance propagated (R2 and R3 do not contain any
   valid information)

   1: audio signal relevance propagated in R2 and R3

   R 2..3 According to table 1 of [BDBOS-BIP20]

   +-------+-----------------------------------------------------------+
   | value |                         relevance                         |
   +-------+-----------------------------------------------------------+
   |   00  |        no audio signal relevance (level ? -72 dBm0)       |
   |   01  |   low audio signal relevance (-52dBm0 ? level > -72dBm0)  |
   |   10  | medium audio signal relevance (-32dBm0 ? level > -52dBm0) |
   |   11  |   high audio signal relevance (0dBm0 ? level > -32dBm0)   |
   +-------+-----------------------------------------------------------+








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4.3.7.  S: Spare (7 bits)

   Those bits are reserved for future use and set to "0" currently.

4.4.  Payload Data

   Reference [ETSI-TETRA-ISI] contains the definition for the generation
   of the codec data.  Data bits D1..D137 in chapter 8 correspond to the
   "Bit number in speech frame" row of table 4 of [ETSI-TETRA-ISI].

   The payload itself contains TETRA ACELP coded speech information
   encoded according to table 4 of [ETSI-TETRA-Codec].

5.  Payload example

   The following example shows how a first and a consecutive 30 ms frame
   is combined into a single 60ms RTP packet.  Note: This example shows
   of usage of OSTE mapping.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |1|1|  CTRL   |C|0|0|0|0|0|0|0|0|D(1)                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                           D(137)|  S          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0|1|  CTRL   |C|0|0|0|0|0|0|0|0|D(1)                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                           D(137)|  S          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Both halves of information contain exact the same CTRL bits







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6.  Congestion Control Considerations

   Tetra uses a fixed bitrate which cannot be adjusted at all.

   Since UDP does not provide congestion control, applications that use
   RTP over UDP SHOULD implement their own congestion control above the
   UDP layer RFC8085 [RFC8085] and MAY also implement a transport
   circuit breaker RFC8083 [RFC8083].  Work in the RMCAT working group
   [RMCAT] describes the interactions and conceptual interfaces
   necessary between the application components that relate to
   congestion control, including the RTP layer, the higher-level media
   codec control layer, and the lower-level transport interface, as well
   as components dedicated to congestion control functions.

   Congestion control for RTP SHALL be used in accordance with RFC 3550
   [RFC3550], and with any applicable RTP profile; e.g., RFC 3551
   [RFC3551].  An additional requirement if best-effort service is being
   used is: users of this payload format MUST monitor packet loss to
   ensure that the packet loss rate is within acceptable parameters.

7.  Payload Format Parameters

   This RTP payload format is identified using one media subtype (audio/
   TETRA) which is registered in accordance with RFC 4855 [RFC4855] and
   per media type registration template from RFC 6838 [RFC6838].

7.1.  Media Type Definition

   The media type for the TETRA codec is expected to be allocated from
   the IETF tree once this draft turns into an RFC.  This media type
   registration covers both real-time transfer via RTP and non-real-time
   transfers via stored files.

   Media Type name:
      audio
   Media Subtype name:
      TETRA
   Required parameters:
      none

   Optional parameters:

   These parameters apply to RTP transfer only.

   maxptime:
      The maximum amount of media which can be encapsulated in a payload
      packet, expressed as time in milliseconds.  The time is calculated
      as the sum of the time that the media present in the packet



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      represents.  The time SHOULD be an integer multiple of the frame
      size.  If this parameter is not present, the sender MAY
      encapsulate any number of speech frames into one RTP packet.
   ptime:
      see RFC 4566 [RFC4566].
   Security considerations:
      See Section Section 10 of RFC XXXX.  [RFC Editor: Upon publication
      as an RFC, please replace "XXXX" with the number assigned to this
      document and remove this note.]

   Interoperability considerations:

   Published specification:

   Applications that use this media type:

   This media type is used in applications needing transport or storage
   of encoded voice.  Some examples include; Voice over IP, streaming
   media, voice messaging, and voice recording on recording systems.

   Intended usage:
      COMMON

8.  Mapping to SDP

   The information carried in the media type specification has a
   specific mapping to fields in the Session Description Protocol
   [RFC4566], which is commonly used to describe RTP sessions.  When SDP
   is used to specify sessions employing the TETRA codec, the mapping is
   as follows:

   Media Type name:
      audio
   Media subtype name:
      TETRA
   Required parameters:
      none
   Optional parameters:
      none
   Mapping Parameters into SDP
      The information carried in the media type specification has a
      specific mapping to fields in the Session Description Protocol
      [RFC4566], which is commonly used to describe RTP sessions.  When
      SDP is used to specify sessions employing the TETRA codec, the
      mapping is as follows:

      *  The media type ("audio") goes in SDP "m=" as the media name.




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      *  The media subtype (payload format name) goes in SDP "a=rtpmap"
         as the encoding name.  The RTP clock rate in "a=rtpmap" MUST be
         8000.
      *  The parameters "ptime" and "maxptime" go in the SDP "a=ptime"
         and "a=maxptime" attributes, respectively.
      *  Any remaining parameters go in the SDP "a=fmtp" attribute by
         copying them directly from the media type parameter string as a
         semicolon-separated list of parameter=value pairs.

   Here is an example SDP session of usage of TETRA:

                         m=audio 49120 RTP/AVP 99
                         a=rtpmap:99 TETRA/8000
                         a=maxptime:60
                         a=ptime:60

8.1.  Offer/Answer Considerations

   The following considerations apply when using SDP Offer-Answer
   procedures to negotiate the use of TETRA payload in RTP:

   o  In most cases, the parameters "maxptime" and "ptime" will not
      affect interoperability; however, the setting of the parameters
      can affect the performance of the application.  The SDP offer-
      answer handling of the "ptime" and "maxptime" parameter is
      described in RFC3264 [RFC3264].
   o  Integer multiples of 30ms SHALL be used for ptime.  It is
      recommended to use packet size of 60ms.  Even if there is no good
      reason why not doing so, there is no need that ptime and maxptime
      parameters are negotiated symmetrically.
   o  Any unknown parameter in an offer SHALL be removed in the answer.

8.2.  Declarative SDP Considerations

   For declarative media, the "ptime" and "maxptime" parameter specifies
   the possible variants used by the sender.

9.  IANA Considerations

   This memo requests that IANA registers [audio/TETRA] from section
   Section 7.1.  The media type is also requested to be added to the
   IANA registry for "RTP Payload Format MIME types"
   (<http://www.iana.org/assignments/rtp-parameters>).








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10.  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.  The
   main security considerations for the RTP packet carrying the RTP
   payload format defined within this memo are confidentiality,
   integrity and source authenticity.  Confidentiality is achieved by
   encryption of the RTP payload.  Integrity of the RTP packets through
   suitable cryptographic integrity protection mechanism.  Cryptographic
   systems may also allow the authentication of the source of the
   payload.  A suitable security mechanism for this RTP payload format
   should provide confidentiality, integrity protection and at least
   source authentication capable of determining if an RTP packet is from
   a member of the RTP session or not.

   Note that the appropriate mechanism to provide security to RTP and
   payloads following this memo may vary.  It is dependent on the
   application, the transport, and the signaling protocol employed.
   Therefore a single mechanism is not sufficient, although if suitable
   the usage of SRTP [RFC3711] is recommended.  Other mechanism that may
   be used are IPsec [RFC4301] and TLS [RFC5246] (RTP over TCP), but
   also other alternatives may exist.

11.  References

11.1.  Normative References

   [BDBOS-BIP20]
              Bundesanstalt fuer den Digitalfunk der Behoerden und
              Organisationen mit Sicherheitsaufgaben, "BIP 20 QOS
              Dienstguete-Parameter BOS-Interoperabilitaetsprofil fuer
              Endgeraete zur Nutzung im Digitalfunk BOS; Version 2014-04
              - Revision 2", 2014.

   [ETSI-TETRA-Codec]
              European Telecommunications Standards Institute, "EN 300
              395-2; Terrestrial Trunked Radio (TETRA); Speech codec for
              full-rate traffic channel; Part 2: TETRA codec V1.3.1",
              2005, <http://www.etsi.org/deliver/
              etsi_en/300300_300399/30039502/01.03.01_60/
              en_30039502v010301p.pdf>.









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   [ETSI-TETRA-ISI]
              European Telecommunications Standards Institute, "TS 100
              392-3-6; Terrestrial Trunked Radio (TETRA); Voice plus
              Data (V+D); Part 3: Interworking at the Inter-System
              Interface (ISI); Sub-part 6: Speech format implementation
              for circuit mode transmission V1.1.1", 2003,
              <http://www.etsi.org/deliver/
              etsi_ts/100300_100399/1003920306/01.01.01_60/
              ts_1003920306v010101p.pdf>.

   [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>.

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
              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", STD 65, RFC 3551,
              DOI 10.17487/RFC3551, July 2003,
              <https://www.rfc-editor.org/info/rfc3551>.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
              July 2006, <https://www.rfc-editor.org/info/rfc4566>.

   [RFC8083]  Perkins, C. and V. Singh, "Multimedia Congestion Control:
              Circuit Breakers for Unicast RTP Sessions", RFC 8083,
              DOI 10.17487/RFC8083, March 2017,
              <https://www.rfc-editor.org/info/rfc8083>.

   [RFC8085]  Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
              Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
              March 2017, <https://www.rfc-editor.org/info/rfc8085>.

11.2.  Informative References

   [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>.







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   [RFC3264]  Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
              with Session Description Protocol (SDP)", RFC 3264,
              DOI 10.17487/RFC3264, June 2002,
              <https://www.rfc-editor.org/info/rfc3264>.

   [RFC3711]  Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
              Norrman, "The Secure Real-time Transport Protocol (SRTP)",
              RFC 3711, DOI 10.17487/RFC3711, March 2004,
              <https://www.rfc-editor.org/info/rfc3711>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

   [RFC4855]  Casner, S., "Media Type Registration of RTP Payload
              Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
              <https://www.rfc-editor.org/info/rfc4855>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/info/rfc6838>.

   [RFC8088]  Westerlund, M., "How to Write an RTP Payload Format",
              RFC 8088, DOI 10.17487/RFC8088, May 2017,
              <https://www.rfc-editor.org/info/rfc8088>.

   [RMCAT]    RTP Media Congestion Avoidance Techniques (rmcat) Working
              Group, "RTP Media Congestion Avoidance Techniques (rmcat)
              Working Grooup", 2018,
              <https://datatracker.ietf.org/wg/rmcat/about/>.

Authors' Addresses

   Andreas Reisenbauer
   Frequentis AG
   Innovationsstr. 1
   Vienna  1100
   Austria

   Email: andreas.reisenbauer@frequentis.com





Reisenbauer, et al.     Expires October 24, 2018               [Page 13]


Internet-Draft  RTP Payload Format for TETRA Audio codec      April 2018


   Udo Brandhuber
   eurofunk Kappacher GmbH
   Germany

   Email: ubrandhuber@eurofunk.com


   Joachim Hagedorn
   Hagedorn Informationssysteme GmbH
   Germany

   Email: joachim@hagedorn-infosysteme.de


   Klaus-Peter Hoehnsch
   T-Systems International GmbH
   Germany

   Email: klaus-peter.hoehnsch@t-systems.com


   Stefan Wenk
   Frequentis AG
   Innovationsstr. 1
   Vienna  1100
   Austria

   Email: stefan.wenk@frequentis.com























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