Internet DRAFT - draft-ietf-payload-tetra
draft-ietf-payload-tetra
payload Reisenbauer
Internet-Draft Frequentis
Intended status: Standards Track Brandhuber
Expires: January 27, 2020 eurofunk
Hagedorn
Hagedorn
Hoehnsch
T-Systems
Wenk
Frequentis
July 26, 2019
RTP Payload Format for the TETRA Audio Codec
draft-ietf-payload-tetra-03
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 January 27, 2020.
Copyright Notice
Copyright (c) 2019 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 . . . . . . . . . . . . . . . . . . 6
4.3.3. CTRL: Control bit(5 bits) . . . . . . . . . . . . . . 6
4.3.4. C bit: Failed Crypto operation indication . . . . . . 6
4.3.5. FRAME_NR: FN (5 bits) . . . . . . . . . . . . . . . . 7
4.3.6. R: Audio Signal Relevance (3 bits) . . . . . . . . . 7
4.3.7. S: Spare (7 bits) . . . . . . . . . . . . . . . . . . 7
4.4. Payload Data . . . . . . . . . . . . . . . . . . . . . . 8
5. Payload example . . . . . . . . . . . . . . . . . . . . . . . 8
6. Congestion Control Considerations . . . . . . . . . . . . . . 8
7. Payload Format Parameters . . . . . . . . . . . . . . . . . . 9
7.1. Media Type Definition . . . . . . . . . . . . . . . . . . 9
8. Mapping to SDP . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Offer/Answer Considerations . . . . . . . . . . . . . . . 11
8.2. Declarative SDP Considerations . . . . . . . . . . . . . 11
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
10. Security Considerations . . . . . . . . . . . . . . . . . . . 12
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1. Normative References . . . . . . . . . . . . . . . . . . 12
11.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
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
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 these 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 is specified
for TDM lines with 2048 kBit/s within traditional circuit mode based
TETRA system. 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
differ 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 audio and control payload 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
RTP payload is composed of multiple blocks with TETRA audio data.
TETRA Audio data itself contains: - Audio Payload Header - Audio Data
(137 Bit) - 7 Spare Bits
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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RTP payload can be formed by any integer multiple of 30ms audio using
following layout (e.g. 90ms audio payload):
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|I|F| CTRL |C|FRAME_NR | R |D(1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| D(137)| S |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|I|F| CTRL |C|FRAME_NR | R |D(1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| D(137)| S |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
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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 derived from the information propagated according table 5.7
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 derived from the information propagated according table 5.7
of [ETSI-TETRA-ISI].
+-------+------------------------+------------------------+
| Value | Sub block 1 | Sub block 2 |
+-------+------------------------+------------------------+
| 00 | no bad frame indicator | no bad frame indicator |
| 01 | no bad frame indicator | bad frame indicator(s) |
| 10 | bad frame indicator(s) | no bad frame indicator |
| 11 | bad frame indicator(s) | bad frame indicator(s) |
+-------+------------------------+------------------------+
NOTE: The interpretation of C4 and C5 is outside the scope of the
present document
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
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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)
The frame number bits contain an uplink frame number as defined in
table 5.3 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) |
+-------+-----------------------------------------------------------+
NOTE: Receiver SHOULD consider stolen or erroneous blocks as not
available for audio decoding as indicated by control bits independent
of audio signal relevance bits.
4.3.7. S: Spare (7 bits)
The S bits bits are reserved for future use and set to "0" currently.
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4.4. Payload Data
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 second consecutive 30
ms frame is combined into a single 60ms RTP packet. Note: This
example shows the 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
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
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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.
Type name:
audio
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 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].
Encoding considerations:
This media type is framed and binary according Section 4.8 of RFC
6838 [RFC6838].
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: N/A
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Published specification:
RFC XXXX [RFC Editor: Upon publication as an RFC, please replace
"XXXX" with the number assigned to this document and remove this
note.]
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.
Additional Information:
- Deprecated alias names for this type: N/A
- Magic number(s): N/A
- File extension(s): N/A
- Macintosh file type code(s): N/A
Person & email address to contact for further information:
Andreas Reisenbauer <mailto:andreas.reisenbauer@frequentis.com>
IETF Payload Working Group <mailto:payload@ietf.org>
Intended usage:
COMMON
Restrictions on usage:
This media subtype depends on RTP framing and hence is only
defined for transfer via RTP RFC 3550 [RFC3550]. Transport within
other framing protocols is not defined at this time.
Author:
Andreas Reisenbauer <mailto:andreas.reisenbauer@frequentis.com>
Change controller:
The IETF PAYLOAD Working Group, or other party as designated by
the IESG.
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
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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.
* 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. 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 specify
the possible variants used by the sender.
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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>).
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]
BDBOS, "BIP 20 QOS Dienstguete-Parameter BOS-
Interoperabilitaetsprofil fuer Endgeraete zur Nutzung im
Digitalfunk BOS; Version 2014-04 - Revision 2", 2014.
[ETSI-TETRA-Codec]
ETSI, "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]
ETSI, "TS 100 392-3-8; Terrestrial Trunked Radio (TETRA);
Voice plus Data (V+D); Part 3: Interworking at the Inter-
System Interface (ISI); Sub-part 8: Generic Speech Format
Implementation V1.3.1", 2018,
<https://www.etsi.org/deliver/
etsi_ts/100300_100399/1003920308/01.03.01_60/
ts_1003920308v010301p.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>.
[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>.
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[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] IETF, "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
Udo Brandhuber
eurofunk Kappacher GmbH
Germany
Email: ubrandhuber@eurofunk.com
Reisenbauer, et al. Expires January 27, 2020 [Page 14]
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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
Reisenbauer, et al. Expires January 27, 2020 [Page 15]
