draft-ietf-mmusic-media-loopback-20.txt   draft-ietf-mmusic-media-loopback-21.txt 
Internet Draft H. Kaplan (ed.) MMUSIC Working Group H. Kaplan (ed.)
Expires: January 30, 2012 Acme Packet Internet-Draft Acme Packet
K. Hedayat Intended status: Proposed Standard K. Hedayat
EXFO Expires: February 6, 2013 EXFO
N. Venna N. Venna
Saperix Saperix
P. Jones P. Jones
Cisco Systems, Inc. Cisco Systems, Inc.
N. Stratton N. Stratton
BlinkMind, Inc. BlinkMind, Inc.
July 30, 2012 August 6, 2012
An Extension to the Session Description Protocol (SDP) An Extension to the Session Description Protocol (SDP)
and Real-time Transport Protocol (RTP) for Media Loopback and Real-time Transport Protocol (RTP) for Media Loopback
draft-ietf-mmusic-media-loopback-20 draft-ietf-mmusic-media-loopback-21
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with This Internet-Draft is submitted to IETF in full conformance with
the provisions of BCP 78 and BCP 79. the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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other groups may also distribute working documents as Internet- working documents as Internet-Drafts. The list of current
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Internet-Drafts are draft documents valid for a maximum of six Internet-Drafts are draft documents valid for a maximum of six
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progress." progress."
The list of current Internet-Drafts can be accessed at This Internet-Draft will expire on February 6, 2013
http://www.ietf.org/ietf/1id-abstracts.txt.
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This Internet-Draft will expire on January 30, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 38 skipping to change at page 2, line 33
attributes, which enable establishment of media sessions where the attributes, which enable establishment of media sessions where the
media is looped back to the transmitter. Such media sessions will media is looped back to the transmitter. Such media sessions will
serve as monitoring and troubleshooting tools by providing the serve as monitoring and troubleshooting tools by providing the
means for measurement of more advanced VoIP, Real-time Text and means for measurement of more advanced VoIP, Real-time Text and
Video over IP performance metrics. Video over IP performance metrics.
Table of Contents Table of Contents
1. Introduction..................................................3 1. Introduction..................................................3
1.1 Use Cases Supported.......................................4 1.1 Use Cases Supported.......................................4
2. Terminology...................................................6 2. Terminology...................................................5
3. Overview of Operation.........................................6 3. Overview of Operation.........................................6
3.1 SDP Offerer Behavior......................................6 3.1 SDP Offerer Behavior......................................6
3.2 SDP Answerer Behavior.....................................6 3.2 SDP Answerer Behavior.....................................6
4. New SDP Attributes............................................7 4. New SDP Attributes............................................7
4.1 Loopback Type Attribute...................................7 4.1 Loopback Type Attribute...................................7
4.2 Loopback Role Attributes: loopback-source and loopback- 4.2 Loopback Role Attributes: loopback-source and loopback-
mirror........................................................8 mirror........................................................8
5. Rules for Generating the SDP offer/answer.....................9 5. Rules for Generating the SDP offer/answer.....................9
5.1 Generating the SDP Offer for Loopback Session.............9 5.1 Generating the SDP Offer for Loopback Session.............9
5.2 Generating the SDP Answer for Loopback Session...........10 5.2 Generating the SDP Answer for Loopback Session...........10
5.3 Offerer Processing of the SDP Answer.....................11 5.3 Offerer Processing of the SDP Answer.....................12
5.4 Modifying the Session....................................12 5.4 Modifying the Session....................................12
5.5 Establishing Sessions Between Entities Behind NAT........12 5.5 Establishing Sessions Between Entities Behind NAT........12
6. RTP Requirements.............................................12 6. RTP Requirements.............................................12
7. Payload formats for Packet loopback..........................13 7. Payload formats for Packet loopback..........................13
7.1 Encapsulated Payload format..............................13 7.1 Encapsulated Payload format..............................13
7.2 Direct loopback RTP payload format.......................16 7.2 Direct loopback RTP payload format.......................16
8. SRTP Behavior................................................17 8. SRTP Behavior................................................17
9. RTCP Requirements............................................17 9. RTCP Requirements............................................17
10. Congestion Control..........................................18 10. Congestion Control..........................................18
11. Examples....................................................18 11. Examples....................................................18
11.1 Offer for specific media loopback type..................18 11.1 Offer for specific media loopback type..................18
11.2 Offer for choice of media loopback type.................19 11.2 Offer for choice of media loopback type.................19
11.3 Answerer rejecting loopback media.......................20 11.3 Answerer rejecting loopback media.......................20
12. Security Considerations.....................................20 12. Security Considerations.....................................20
13. Implementation Considerations...............................21 13. Implementation Considerations...............................21
14. IANA Considerations.........................................22 14. IANA Considerations.........................................22
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8. SRTP Behavior................................................17 8. SRTP Behavior................................................17
9. RTCP Requirements............................................17 9. RTCP Requirements............................................17
10. Congestion Control..........................................18 10. Congestion Control..........................................18
11. Examples....................................................18 11. Examples....................................................18
11.1 Offer for specific media loopback type..................18 11.1 Offer for specific media loopback type..................18
11.2 Offer for choice of media loopback type.................19 11.2 Offer for choice of media loopback type.................19
11.3 Answerer rejecting loopback media.......................20 11.3 Answerer rejecting loopback media.......................20
12. Security Considerations.....................................20 12. Security Considerations.....................................20
13. Implementation Considerations...............................21 13. Implementation Considerations...............................21
14. IANA Considerations.........................................22 14. IANA Considerations.........................................22
[Note to RFC Editor: Please replace "XXXX" with the appropriate RFC
number on publication]..........................................22
14.1 SDP Attributes..........................................22 14.1 SDP Attributes..........................................22
14.2 Media Types.............................................22 14.2 Media Types.............................................23
15. Acknowledgements............................................31 15. Acknowledgements............................................31
16. Normative References........................................31 16. Normative References........................................31
17. Informative References......................................32 17. Informative References......................................32
1. Introduction 1. Introduction
The overall quality, reliability, and performance of VoIP, The overall quality, reliability, and performance of VoIP,
Real-time Text and Video over IP services rely on the performance Real-time Text and Video over IP services rely on the performance
and quality of the media path. In order to assure the quality of and quality of the media path. In order to assure the quality of
the delivered media there is a need to monitor the performance of the delivered media there is a need to monitor the performance of
the media transport. One method of monitoring and managing the the media transport. One method of monitoring and managing the
overall quality of real-time VoIP, Text and Video over IP Services overall quality of real-time VoIP, Text and Video over IP Services
is through monitoring the quality of the media in an active is through monitoring the quality of the media in an active
session. This type of "active monitoring" of services is a method session. This type of "active monitoring" of services is a method
of proactively managing the performance and quality of VoIP based of proactively managing the performance and quality of VoIP based
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type. The packet is taken as close as possible to the analog level, type. The packet is taken as close as possible to the analog level,
then re-encoded according to an outgoing format determined by SDP then re-encoded according to an outgoing format determined by SDP
negotiation. The reencoded content is returned to the loopback negotiation. The reencoded content is returned to the loopback
source as an RTP packet with payload type corresponding to the source as an RTP packet with payload type corresponding to the
reencoding format. reencoding format.
This usage allows trouble-shooting at the codec level. The This usage allows trouble-shooting at the codec level. The
capability for path statistics is limited to what is available from capability for path statistics is limited to what is available from
RTCP reports. RTCP reports.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC 2119. this document are to be interpreted as described in RFC 2119.
SDP: Session Description Protocol, as defined in [RFC4566]. This SDP: Session Description Protocol, as defined in [RFC4566]. This
document assumes the SDP offer/answer model is followed, per document assumes the SDP offer/answer model is followed, per
[RFC3264], but does not assume any specific signaling protocol for [RFC3264], but does not assume any specific signaling protocol for
carrying the SDP. carrying the SDP.
The following terms are borrowed from [RFC3264] definitions: offer, The following terms are borrowed from [RFC3264] definitions: offer,
offerer, answer, answerer, and agent. offerer, answer, answerer, and agent.
3. Overview of Operation 3. Overview of Operation
This document defines two loopback 'types', two 'roles', and two This document defines two loopback 'types', two 'roles', and two
encoding formats for loopback. For any given SDP offerer or encoding formats for loopback. For any given SDP offerer or
answerer pair, one side is the source of RTP packets, while the answerer pair, one side is the source of RTP packets, while the
other is the mirror looping packets/media back. Those define the other is the mirror looping packets/media back. Those define the
two loopback roles. As the mirror, two 'types' of loopback can be two loopback roles. As the mirror, two 'types' of loopback can be
performed: packet-level or media-level. When media-level is used, performed: packet-level or media-level. When media-level is used,
there is no further choice of encoding format - there is only one there is no further choice of encoding format - there is only one
format: whatever is indicated for normal media, since the "looping" format: whatever is indicated for normal media, since the "looping"
is performed at the codec level. When packet-level looping is is performed at the codec level. When packet-level looping is
performed, however, the mirror can either send back RTP in an performed, however, the mirror can either send back RTP in an
encapsulated format or direct-loopback format. The rest of this encapsulated format or direct-loopback format. The rest of this
document describes these loopback types, roles, and encoding document describes these loopback types, roles, and encoding
formats, and the SDP offer/answer rules for indicating them. formats, and the SDP offer/answer rules for indicating them.
3.1 SDP Offerer Behavior 3.1 SDP Offerer Behavior
An SDP offerer compliant to this memo and attempting to establish a An SDP offerer compliant to this memo and attempting to establish a
media session with media loopback MUST include "loopback" media media session with media loopback MUST include "loopback" media
attributes for each individual media description in the offer attributes for each individual media description in the offer
message. The offerer MUST look for the "loopback" media attributes message. The offerer MUST look for the "loopback" media attributes
in the media description(s) of the response from the answer for in the media description(s) of the response from the answer for
confirmation that the request is accepted. confirmation that the request is accepted.
3.2 SDP Answerer Behavior 3.2 SDP Answerer Behavior
An SDP answerer compliant to this specification and receiving an An SDP answerer compliant to this specification and receiving an
offer containing media descriptions with the "loopback" media offer containing media descriptions with the "loopback" media
attributes MUST acknowledge the request by including the received attributes MUST acknowledge the request by including the received
"loopback" media attributes for each media description in its "loopback" media attributes for each media description in its
answer if it agrees to do the loopback. If the answerer does not answer if it agrees to do the loopback. If the answerer does not
want to do loopback or wants to reject the "loopback" request for want to do loopback or wants to reject the "loopback" request for
specific media descriptions, it MUST do so as defined in this specific media descriptions, it MUST do so as defined in this
section. section.
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in the answer as defined in RFC 3264 [RFC3264], or by rejecting the in the answer as defined in RFC 3264 [RFC3264], or by rejecting the
entire offer (i.e., by rejecting the session request entirely). entire offer (i.e., by rejecting the session request entirely).
Note that an answerer that is not compliant to this specification Note that an answerer that is not compliant to this specification
and which receives an offer with the "loopback" media attributes and which receives an offer with the "loopback" media attributes
would ignore the attributes and treat the incoming offer as a would ignore the attributes and treat the incoming offer as a
normal request. If the offerer does not wish to establish a normal request. If the offerer does not wish to establish a
"normal" RTP session, it would need to terminate the session upon "normal" RTP session, it would need to terminate the session upon
receiving such an answer. receiving such an answer.
4. New SDP Attributes 4. New SDP Attributes
Three new SDP media-level attributes are defined: one indicates the Three new SDP media-level attributes are defined: one indicates the
type of loopback, and the other two define the role of the agent. type of loopback, and the other two define the role of the agent.
4.1 Loopback Type Attribute 4.1 Loopback Type Attribute
This specification defines a new 'loopback' attribute, which This specification defines a new 'loopback' attribute, which
indicates that the agent wishes to perform loopback, and the type indicates that the agent wishes to perform loopback, and the type
of loopack that the agent is able to do. The loopback-type is a of loopack that the agent is able to do. The loopback-type is a
value media attribute [RFC4566] with the following syntax: value media attribute [RFC4566] with the following syntax:
a=loopback:<loopback-type> a=loopback:<loopback-type>
Following is the Augmented BNF [RFC5234] for loopback-type: Following is the Augmented BNF [RFC5234] for loopback-type:
loopback-attr = "a=loopback:" SP loopback-type attribute /= loopback-attr
; attribute defined in RFC 4566
loopback-attr = "loopback:" SP loopback-type
loopback-type = loopback-choice [1*SP loopback-choice] loopback-type = loopback-choice [1*SP loopback-choice]
loopback-choice = loopback-type-pkt / loopback-type-media loopback-choice = loopback-type-pkt / loopback-type-media
loopback-type-pkt = "rtp-pkt-loopback" loopback-type-pkt = "rtp-pkt-loopback"
loopback-type-media = "rtp-media-loopback" loopback-type-media = "rtp-media-loopback"
The loopback-type is used to indicate the type of loopback. The The loopback-type is used to indicate the type of loopback. The
loopback-type values are rtp-pkt-loopback, and rtp-media-loopback. loopback-type values are rtp-pkt-loopback, and rtp-media-loopback.
rtp-pkt-loopback: In this mode, the RTP packets are looped back to rtp-pkt-loopback: In this mode, the RTP packets are looped back to
the sender at a point before the encoder/decoder function in the the sender at a point before the encoder/decoder function in the
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formats that MUST be used for this type of loopback. This type of formats that MUST be used for this type of loopback. This type of
loopback applies to the encapsulated and direct loopback use-cases loopback applies to the encapsulated and direct loopback use-cases
described in Section 1.1. described in Section 1.1.
rtp-media-loopback: This loopback is activated as close as possible rtp-media-loopback: This loopback is activated as close as possible
to the analog interface and after the decoder so that the RTP to the analog interface and after the decoder so that the RTP
packets are subsequently re-encoded prior to transmission back to packets are subsequently re-encoded prior to transmission back to
the sender. This type of loopback applies to the media loopback the sender. This type of loopback applies to the media loopback
use-case described in Section 1.1.3. use-case described in Section 1.1.3.
4.2 Loopback Role Attributes: loopback-source and loopback-mirror 4.2 Loopback Role Attributes: loopback-source and loopback-mirror
The loopback role defines two property media attributes [RFC4566] The loopback role defines two property media attributes [RFC4566]
that are used to indicate the role of the agent generating the SDP that are used to indicate the role of the agent generating the SDP
offer or answer. The syntax of the two loopback role media offer or answer. The syntax of the two loopback role media
attributes are as follows: attributes are as follows:
a=loopback-source a=loopback-source
and and
a=loopback-mirror a=loopback-mirror
Following is the Augmented BNF [RFC5234] for loopback-type:
attribute /= loopback-source / loopback-mirror
; attribute defined in RFC 4566
loopback-source = "loopback-source"
loopback-mirror = "loopback-mirror"
loopback-source: This attribute specifies that the entity that loopback-source: This attribute specifies that the entity that
generated the SDP is the media source and expects the receiver of generated the SDP is the media source and expects the receiver of
the SDP message to act as a loopback-mirror. the SDP message to act as a loopback-mirror.
loopback-mirror: This attribute specifies that the entity that loopback-mirror: This attribute specifies that the entity that
generated the SDP will mirror (echo) all received media back to the generated the SDP will mirror (echo) all received media back to the
sender of the RTP stream. No media is generated locally by the sender of the RTP stream. No media is generated locally by the
looping back entity for transmission in the mirrored stream. looping back entity for transmission in the mirrored stream.
The "m=" line in the SDP MUST include all the payload types that The "m=" line in the SDP MUST include all the payload types that
will be used during the loopback session. The complete payload will be used during the loopback session. The complete payload
space for the session is specified in the "m=" line and the rtpmap space for the session is specified in the "m=" line and the rtpmap
attribute is used to map from the payload type number to an attribute is used to map from the payload type number to an
encoding name denoting the payload format to be used. encoding name denoting the payload format to be used.
5. Rules for Generating the SDP offer/answer 5. Rules for Generating the SDP offer/answer
5.1 Generating the SDP Offer for Loopback Session 5.1 Generating the SDP Offer for Loopback Session
If an offerer wishes to make a loopback request, it MUST include If an offerer wishes to make a loopback request, it MUST include
both the loopback-type and loopback-role attributes in a valid SDP both the loopback-type and loopback-role attributes in a valid SDP
offer: offer:
Example: m=audio 41352 RTP/AVP 0 8 100 Example: m=audio 41352 RTP/AVP 0 8 100
a=loopback:rtp-media-loopback a=loopback:rtp-media-loopback
a=loopback-source a=loopback-source
a=rtpmap:0 pcmu/8000 a=rtpmap:0 pcmu/8000
a=rtpmap:8 pcma/8000 a=rtpmap:8 pcma/8000
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Example: m=audio 41352 RTP/AVP 0 8 112 Example: m=audio 41352 RTP/AVP 0 8 112
a=loopback:rtp-pkt-loopback a=loopback:rtp-pkt-loopback
a=loopback-source a=loopback-source
a=rtpmap:112 encaprtp/8000 a=rtpmap:112 encaprtp/8000
Example: m=audio 41352 RTP/AVP 0 8 112 Example: m=audio 41352 RTP/AVP 0 8 112
a=loopback:rtp-pkt-loopback a=loopback:rtp-pkt-loopback
a=loopback-source a=loopback-source
a=rtpmap:112 rtploopback/8000 a=rtpmap:112 rtploopback/8000
5.2 Generating the SDP Answer for Loopback Session 5.2 Generating the SDP Answer for Loopback Session
As with the offer, an SDP answer for loopback MUST follow SDP As with the offer, an SDP answer for loopback MUST follow SDP
offer/answer rules for the direction attribute, but directions of offer/answer rules for the direction attribute, but directions of
"sendonly" or "recvonly" do not apply for loopback operation and "sendonly" or "recvonly" do not apply for loopback operation and
hence MUST NOT be used. hence MUST NOT be used.
The port number and the address in the answer (m/c= lines) indicate The port number and the address in the answer (m/c= lines) indicate
where the answerer would like to receive the media stream. The where the answerer would like to receive the media stream. The
payload type numbers indicate the value of the payload types the payload type numbers indicate the value of the payload types the
answerer expects to send and receive. answerer expects to send and receive.
skipping to change at page 11, line 50 skipping to change at page 12, line 5
a=rtpmap:112 encaprtp/8000 a=rtpmap:112 encaprtp/8000
m=audio 12345 RTP/AVP 0 8 113 m=audio 12345 RTP/AVP 0 8 113
a=loopback:rtp-pkt-loopback a=loopback:rtp-pkt-loopback
a=loopback-mirror a=loopback-mirror
a=rtpmap:113 rtploopback/8000 a=rtpmap:113 rtploopback/8000
The previous examples used the 'encaprtp' and 'rtploopback' The previous examples used the 'encaprtp' and 'rtploopback'
encoding names, which will be defined in sections 7.1.3 and 7.2.3. encoding names, which will be defined in sections 7.1.3 and 7.2.3.
5.3 Offerer Processing of the SDP Answer 5.3 Offerer Processing of the SDP Answer
If the received SDP answer does not contain an a=loopback-mirror or If the received SDP answer does not contain an a=loopback-mirror or
a=loopback-source attribute, it is assumed that the loopback a=loopback-source attribute, it is assumed that the loopback
extensions are not supported by the remote agent. This is not a extensions are not supported by the remote agent. This is not a
protocol failure, and instead merely completes the SDP offer/answer protocol failure, and instead merely completes the SDP offer/answer
exchange with whatever normal rules apply; the offerer MAY decide exchange with whatever normal rules apply; the offerer MAY decide
to end the established RTP session (if any) through normal means of to end the established RTP session (if any) through normal means of
the upper-layer signaling protocol (e.g., by sending a SIP BYE). the upper-layer signaling protocol (e.g., by sending a SIP BYE).
5.4 Modifying the Session 5.4 Modifying the Session
At any point during the loopback session, either participant MAY At any point during the loopback session, either participant MAY
issue a new offer to modify the characteristics of the previous issue a new offer to modify the characteristics of the previous
session, as defined in section 8 of RFC 3264 [RFC3264]. This also session, as defined in section 8 of RFC 3264 [RFC3264]. This also
includes transitioning from a normal media processing mode to includes transitioning from a normal media processing mode to
loopback mode, and vice versa. loopback mode, and vice versa.
5.5 Establishing Sessions Between Entities Behind NAT 5.5 Establishing Sessions Between Entities Behind NAT
ICE/STUN/TURN provide a general solution to establishing media ICE/STUN/TURN provide a general solution to establishing media
sessions between entities that are behind NATs, as defined in sessions between entities that are behind NATs, as defined in
[RFC5245]. Loopback sessions that involve one or more endpoints [RFC5245]. Loopback sessions that involve one or more endpoints
behind NATs SHOULD use these general solutions wherever possible. behind NATs SHOULD use these general solutions wherever possible.
Furthermore, if the mirroring entity is behind a NAT, it MUST send Furthermore, if the mirroring entity is behind a NAT, it MUST send
some packets to the identified address/port(s) of the peer, in some packets to the identified address/port(s) of the peer, in
order to open the NAT pinhole. Using ICE this would be order to open the NAT pinhole. Using ICE this would be
accomplished with the STUN connectivity check process, or through a accomplished with the STUN connectivity check process, or through a
TURN server connection. If ICE is not supported, either [RFC6263] TURN server connection. If ICE is not supported, either [RFC6263]
or Section 10 of ICE [RFC5245] SHOULD be followed to open the or Section 10 of ICE [RFC5245] SHOULD be followed to open the
pinhole and keep the NAT binding alive/refreshed. pinhole and keep the NAT binding alive/refreshed.
Note that for any form of NAT traversal to function, symmetric Note that for any form of NAT traversal to function, symmetric
RTP/RTCP [RFC4961] MUST be used. In other words both agents MUST RTP/RTCP [RFC4961] MUST be used. In other words both agents MUST
send packets from the source address and port they receive packets send packets from the source address and port they receive packets
on. on.
6. RTP Requirements 6. RTP Requirements
A loopback source MUST NOT send multiple source streams on the same A loopback source MUST NOT send multiple source streams on the same
5-tuple, since there is no means for the mirror to indicate which 5-tuple, since there is no means for the mirror to indicate which
is which in its mirrored RTP packets. is which in its mirrored RTP packets.
A loopback mirror that is compliant to this specification and A loopback mirror that is compliant to this specification and
accepts media with rtp-pkt-loopback loopback type MUST loopback the accepts media with rtp-pkt-loopback loopback type MUST loopback the
incoming RTP packets using either the encapsulated RTP payload incoming RTP packets using either the encapsulated RTP payload
format or the direct loopback RTP payload format as defined in format or the direct loopback RTP payload format as defined in
section 7 of this specification. section 7 of this specification.
skipping to change at page 13, line 21 skipping to change at page 13, line 22
incoming media MUST be treated as if it were to be played (e.g. the incoming media MUST be treated as if it were to be played (e.g. the
media stream MAY receive treatment from PLC algorithms). The media stream MAY receive treatment from PLC algorithms). The
mirroring entity MUST re-generate all the RTP header fields as it mirroring entity MUST re-generate all the RTP header fields as it
would when transmitting media. The mirroring entity MAY choose to would when transmitting media. The mirroring entity MAY choose to
encode the loopback media according to any of the media encode the loopback media according to any of the media
descriptions supported by the offering entity. Furthermore, in descriptions supported by the offering entity. Furthermore, in
cases where the same media type is looped back, the mirroring cases where the same media type is looped back, the mirroring
entity MAY choose to preserve number of frames/packet and bitrate entity MAY choose to preserve number of frames/packet and bitrate
of the encoded media according to the received media. of the encoded media according to the received media.
7. Payload formats for Packet loopback 7. Payload formats for Packet loopback
The payload formats described in this section MUST be used by a The payload formats described in this section MUST be used by a
loopback-mirror when 'rtp-pkt-loopback' is the specified loopback-mirror when 'rtp-pkt-loopback' is the specified
loopback-type. Two different formats are specified here - an loopback-type. Two different formats are specified here - an
encapsulated RTP payload format and a direct loopback RTP payload encapsulated RTP payload format and a direct loopback RTP payload
format. The encapsulated RTP payload format should be used when format. The encapsulated RTP payload format should be used when
the incoming RTP header information needs to be preserved during the incoming RTP header information needs to be preserved during
the loopback operation. This is useful in cases where loopback the loopback operation. This is useful in cases where loopback
source needs to measure performance metrics in both directions. source needs to measure performance metrics in both directions.
However, this comes at the expense of increased packet size as However, this comes at the expense of increased packet size as
described in section 7.1. The direct loopback RTP payload format described in section 7.1. The direct loopback RTP payload format
should be used when bandwidth requirements prevent the use of should be used when bandwidth requirements prevent the use of
encapsulated RTP payload format. encapsulated RTP payload format.
7.1 Encapsulated Payload format 7.1 Encapsulated Payload format
A received RTP packet is encapsulated in the payload section of the A received RTP packet is encapsulated in the payload section of the
RTP packet generated by a loopback-mirror. Each received packet RTP packet generated by a loopback-mirror. Each received packet
MUST be encapsulated in a separate encapsulating RTP packet; the MUST be encapsulated in a separate encapsulating RTP packet; the
encapsulated packet MUST be fragmented only if required (for encapsulated packet MUST be fragmented only if required (for
example: due to MTU limitations). example: due to MTU limitations).
7.1.1 Usage of RTP Header fields 7.1.1 Usage of RTP Header fields
Payload Type (PT): The assignment of an RTP payload type for this Payload Type (PT): The assignment of an RTP payload type for this
skipping to change at page 16, line 12 skipping to change at page 16, line 12
negotiated using SDP. There is no static payload type assignment negotiated using SDP. There is no static payload type assignment
for the encapsulating stream, so dynamic payload type numbers MUST for the encapsulating stream, so dynamic payload type numbers MUST
be used. The binding to the name is indicated by an rtpmap be used. The binding to the name is indicated by an rtpmap
attribute. The name used in this binding is "encaprtp". attribute. The name used in this binding is "encaprtp".
The following is an example SDP fragment for encapsulated RTP. The following is an example SDP fragment for encapsulated RTP.
m=audio 41352 RTP/AVP 112 m=audio 41352 RTP/AVP 112
a=rtpmap:112 encaprtp/8000 a=rtpmap:112 encaprtp/8000
7.2 Direct loopback RTP payload format 7.2 Direct loopback RTP payload format
The direct loopback RTP payload format can be used in scenarios The direct loopback RTP payload format can be used in scenarios
where the 16 byte overhead of the encapsulated payload format is of where the 16 byte overhead of the encapsulated payload format is of
concern, or simply due to local policy. When using this payload concern, or simply due to local policy. When using this payload
format, the receiver MUST loop back each received RTP packet format, the receiver MUST loop back each received RTP packet
payload (not header) in a separate RTP packet. payload (not header) in a separate RTP packet.
Because a direct loopback format does not retain the original RTP Because a direct loopback format does not retain the original RTP
headers, there will be no indication of the original payload-type headers, there will be no indication of the original payload-type
sent to the mirror, in looped-back packets. Therefore, the sent to the mirror, in looped-back packets. Therefore, the
skipping to change at page 17, line 26 skipping to change at page 17, line 26
type assignment for the stream, so dynamic payload type numbers type assignment for the stream, so dynamic payload type numbers
MUST be used. The binding to the name is indicated by an rtpmap MUST be used. The binding to the name is indicated by an rtpmap
attribute. The name used in this binding is "rtploopback". attribute. The name used in this binding is "rtploopback".
The following is an example SDP fragment for direct loopback RTP The following is an example SDP fragment for direct loopback RTP
format. format.
m=audio 41352 RTP/AVP 112 m=audio 41352 RTP/AVP 112
a=rtpmap:112 rtploopback/8000 a=rtpmap:112 rtploopback/8000
8. SRTP Behavior 8. SRTP Behavior
Secure RTP [RFC3711] MAY be used for loopback sessions. SRTP Secure RTP [RFC3711] MAY be used for loopback sessions. SRTP
operates at a lower logical layer than RTP, and thus if both sides operates at a lower logical layer than RTP, and thus if both sides
negotiate to use SRTP, each side uses its own key, performs negotiate to use SRTP, each side uses its own key, performs
encryption/decryption, authentication, etc. Therefore the loopback encryption/decryption, authentication, etc. Therefore the loopback
function on the mirror occurs after the SRTP packet has been function on the mirror occurs after the SRTP packet has been
decrypted and authenticated, as a normal cleartext RTP packet decrypted and authenticated, as a normal cleartext RTP packet
without an MKI or authentication tag; once the cleartext RTP packet without an MKI or authentication tag; once the cleartext RTP packet
or payload is mirrored - either at the media-layer, direct packet- or payload is mirrored - either at the media-layer, direct packet-
layer, or encapsulated packet-layer - it is encrypted by the mirror layer, or encapsulated packet-layer - it is encrypted by the mirror
using its own key. using its own key.
9. RTCP Requirements 9. RTCP Requirements
The use of the loopback attribute is intended for monitoring of The use of the loopback attribute is intended for monitoring of
media quality of the session. Consequently the media performance media quality of the session. Consequently the media performance
information should be exchanged between the offering and the information should be exchanged between the offering and the
answering entities. An offering or answering agent that is answering entities. An offering or answering agent that is
compliant to this specification SHOULD support RTCP per [RFC3550] compliant to this specification SHOULD support RTCP per [RFC3550]
and RTCP-XR per RFC 3611 [RFC3611]. Furthermore, if the offerer or and RTCP-XR per RFC 3611 [RFC3611]. Furthermore, if the offerer or
answerer choose to support RTCP-XR, they SHOULD support RTCP-XR answerer choose to support RTCP-XR, they SHOULD support RTCP-XR
Loss RLE report block, Duplicate RLE report block, Statistics Loss RLE report block, Duplicate RLE report block, Statistics
Summary report block, and VoIP Metric Reports Block per sections Summary report block, and VoIP Metric Reports Block per sections
4.1, 4.2, 4.6, and 4.7 of RFC 3611 [RFC3611]. The offerer and the 4.1, 4.2, 4.6, and 4.7 of RFC 3611 [RFC3611]. The offerer and the
answerer MAY support other RTCP-XR reporting blocks as defined by answerer MAY support other RTCP-XR reporting blocks as defined by
RFC 3611 [RFC3611]. RFC 3611 [RFC3611].
10. Congestion Control 10. Congestion Control
All the participants in a media-level loopback session SHOULD All the participants in a media-level loopback session SHOULD
implement congestion control mechanisms as defined by the RTP implement congestion control mechanisms as defined by the RTP
profile under which the loopback mechanism is implemented. For profile under which the loopback mechanism is implemented. For
audio video profiles, implementations SHOULD conform to the audio video profiles, implementations SHOULD conform to the
mechanism defined in Section 2 of RFC 3551. mechanism defined in Section 2 of RFC 3551.
For packet-level loopback types, the loopback source SHOULD For packet-level loopback types, the loopback source SHOULD
implement congestion control. The mirror will simply reflect back implement congestion control. The mirror will simply reflect back
the RTP packets it receives (either in encapsulated or direct the RTP packets it receives (either in encapsulated or direct
modes), therefore the source needs to control the congestion of modes), therefore the source needs to control the congestion of
both forward and reverse paths by reducing its sending rate to the both forward and reverse paths by reducing its sending rate to the
mirror. This keeps the loopback mirror implementation simpler, and mirror. This keeps the loopback mirror implementation simpler, and
provides more flexibility for the source performing a loopback provides more flexibility for the source performing a loopback
test. test.
11. Examples 11. Examples
This section provides examples for media descriptions using SDP for This section provides examples for media descriptions using SDP for
different scenarios. The examples are given for SIP-based different scenarios. The examples are given for SIP-based
transactions and are abbreviated and do not show the complete transactions and are abbreviated and do not show the complete
signaling for convenience. signaling for convenience.
11.1 Offer for specific media loopback type 11.1 Offer for specific media loopback type
An agent sends an SDP offer which looks like: An agent sends an SDP offer which looks like:
v=0 v=0
o=alice 2890844526 2890842807 IN IP4 host.atlanta.example.com o=alice 2890844526 2890842807 IN IP4 host.atlanta.example.com
s=- s=-
c=IN IP4 host.atlanta.example.com c=IN IP4 host.atlanta.example.com
t=0 0 t=0 0
m=audio 49170 RTP/AVP 0 m=audio 49170 RTP/AVP 0
a=loopback:rtp-media-loopback a=loopback:rtp-media-loopback
skipping to change at page 19, line 20 skipping to change at page 19, line 20
c=IN IP4 host.biloxi.example.com c=IN IP4 host.biloxi.example.com
t=0 0 t=0 0
m=audio 49270 RTP/AVP 0 m=audio 49270 RTP/AVP 0
a=loopback:rtp-media-loopback a=loopback:rtp-media-loopback
a=loopback-mirror a=loopback-mirror
a=rtpmap:0 pcmu/8000 a=rtpmap:0 pcmu/8000
The answerer is accepting to mirror the media from the offerer at The answerer is accepting to mirror the media from the offerer at
the media level. the media level.
11.2 Offer for choice of media loopback type 11.2 Offer for choice of media loopback type
An agent sends an SDP offer which looks like: An agent sends an SDP offer which looks like:
v=0 v=0
o=alice 2890844526 2890842807 IN IP4 host.atlanta.example.com o=alice 2890844526 2890842807 IN IP4 host.atlanta.example.com
s=- s=-
c=IN IP4 host.atlanta.example.com c=IN IP4 host.atlanta.example.com
t=0 0 t=0 0
m=audio 49170 RTP/AVP 0 112 113 m=audio 49170 RTP/AVP 0 112 113
a=loopback:rtp-media-loopback rtp-pkt-loopback a=loopback:rtp-media-loopback rtp-pkt-loopback
skipping to change at page 20, line 7 skipping to change at page 20, line 7
c=IN IP4 host.biloxi.example.com c=IN IP4 host.biloxi.example.com
t=0 0 t=0 0
m=audio 49270 RTP/AVP 0 112 m=audio 49270 RTP/AVP 0 112
a=loopback:rtp-pkt-loopback a=loopback:rtp-pkt-loopback
a=loopback-mirror a=loopback-mirror
a=rtpmap:0 pcmu/8000 a=rtpmap:0 pcmu/8000
a=rtpmap:112 encaprtp/8000 a=rtpmap:112 encaprtp/8000
The answerer is accepting to mirror the media from the offerer at The answerer is accepting to mirror the media from the offerer at
the packet level using the encapsulated RTP payload format. the packet level using the encapsulated RTP payload format.
11.3 Answerer rejecting loopback media 11.3 Answerer rejecting loopback media
An agent sends an SDP offer which looks like: An agent sends an SDP offer which looks like:
v=0 v=0
o=alice 2890844526 2890842807 IN IP4 host.atlanta.example.com o=alice 2890844526 2890842807 IN IP4 host.atlanta.example.com
s=- s=-
c=IN IP4 host.atlanta.example.com c=IN IP4 host.atlanta.example.com
t=0 0 t=0 0
m=audio 49170 RTP/AVP 0 m=audio 49170 RTP/AVP 0
a=loopback:rtp-media-loopback a=loopback:rtp-media-loopback
skipping to change at page 20, line 43 skipping to change at page 20, line 43
Note in this case the answerer did not indicate loopback support, Note in this case the answerer did not indicate loopback support,
although it could have and still used a port number of 0 to although it could have and still used a port number of 0 to
indicate it does not wish to accept that media session. indicate it does not wish to accept that media session.
Alternatively, the answering agent could have simply rejected the Alternatively, the answering agent could have simply rejected the
entire SDP offer through some higher-layer signaling protocol means entire SDP offer through some higher-layer signaling protocol means
(e.g., by rejecting the SIP INVITE request if the SDP offer was in (e.g., by rejecting the SIP INVITE request if the SDP offer was in
the INVITE). the INVITE).
12. Security Considerations 12. Security Considerations
The security considerations of [RFC3264] and [RFC3550] apply. The security considerations of [RFC3264] and [RFC3550] apply.
Given that media loopback may be automated without the end user's Given that media loopback may be automated without the end user's
knowledge, the answerer of the media loopback should be aware of knowledge, the answerer of the media loopback should be aware of
denial of service attacks. It is RECOMMENDED that session requests denial of service attacks. It is RECOMMENDED that session requests
for media loopback be authenticated and the frequency of such for media loopback be authenticated and the frequency of such
sessions limited by the answerer. sessions limited by the answerer.
If the higher-layer signaling protocol were not authenticated, a If the higher-layer signaling protocol were not authenticated, a
skipping to change at page 21, line 38 skipping to change at page 21, line 38
does not terminate properly and the end device does not have a does not terminate properly and the end device does not have a
timeout mechanism for such. timeout mechanism for such.
For the reasons noted above, end user devices SHOULD provide a For the reasons noted above, end user devices SHOULD provide a
means of indicating to the human user that the device is in a means of indicating to the human user that the device is in a
loopback session, even if it is an authenticated session. Devices loopback session, even if it is an authenticated session. Devices
that answer or generate loopback sessions SHOULD either perform that answer or generate loopback sessions SHOULD either perform
keepalive/refresh tests of the session state through some means, or keepalive/refresh tests of the session state through some means, or
time out the session automatically. time out the session automatically.
13. Implementation Considerations 13. Implementation Considerations
The media loopback approach described in this document is a The media loopback approach described in this document is a
complete solution that would work under all scenarios. However, it complete solution that would work under all scenarios. However, it
is possible that the solution may not be light-weight enough for is possible that the solution may not be light-weight enough for
some implementations. In light of this concern, this section some implementations. In light of this concern, this section
clarifies which features of the loopback proposal MUST be clarifies which features of the loopback proposal MUST be
implemented for all implementations and which features MAY be implemented for all implementations and which features MAY be
deferred if the complete solution is not desired. deferred if the complete solution is not desired.
All implementations MUST at least support the rtp-pkt-loopback mode All implementations MUST at least support the rtp-pkt-loopback mode
for loopback-type, with direct media loopback payload encoding. In for loopback-type, with direct media loopback payload encoding. In
addition, for the loopback role, all implementations of an SDP addition, for the loopback role, all implementations of an SDP
offerer MUST at least be able to act as a loopback-source. offerer MUST at least be able to act as a loopback-source.
14. IANA Considerations 14. IANA Considerations
14.1 SDP Attributes [Note to RFC Editor: Please replace "XXXX" with the appropriate RFC
number on publication]
14.1 SDP Attributes
This document defines three new media-level SDP attributes. IANA This document defines three new media-level SDP attributes. IANA
has registered the following attributes: has registered the following attributes:
Contact name: Kaynam Hedayat Contact name: Kaynam Hedayat
<kaynam.hedayat@exfo.com>. Email address: kaynam.hedayat@exfo.com
Telephone number: +1-978-367-5611
Attribute name: loopback Attribute name: loopback
Type of attribute: Media level. Type of attribute: Media level.
Subject to charset: No. Subject to charset: No.
Purpose of attribute: The 'loopback' attribute is used to Purpose of attribute: The 'loopback' attribute is used to
indicate the type of media loopback. indicate the type of media loopback.
Allowed attribute values: The parameters to 'loopback' may be Allowed attribute values: The parameters to 'loopback' may be
one or more of "rtp-pkt-loopback" and one or more of "rtp-pkt-loopback" and
"rtp-media-loopback". See section 5 "rtp-media-loopback". See section 5
of this document for syntax. of RFC XXXX for syntax.
Contact name: Kaynam Hedayat Contact name: Kaynam Hedayat
<kaynam.hedayat@exfo.com>. Email address: kaynam.hedayat@exfo.com
Telephone number: +1-978-367-5611
Attribute name: loopback-source Attribute name: loopback-source
Type of attribute: Media level. Type of attribute: Media level.
Subject to charset: No. Subject to charset: No.
Purpose of attribute: The 'loopback-source' attribute Purpose of attribute: The 'loopback-source' attribute
specifies that the sender is the media specifies that the sender is the media
source and expects the receiver to act source and expects the receiver to act
as a loopback-mirror. as a loopback-mirror.
Allowed attribute values: None. Allowed attribute values: None.
Contact name: Kaynam Hedayat Contact name: Kaynam Hedayat
<kaynam.hedayat@exfo.com>. Email address: kaynam.hedayat@exfo.com
Telephone number: +1-978-367-5611
Attribute name: loopback-mirror Attribute name: loopback-mirror
Type of attribute: Media level. Type of attribute: Media level.
Subject to charset: No. Subject to charset: No.
Purpose of attribute: The 'loopback-mirror' attribute Purpose of attribute: The 'loopback-mirror' attribute
specifies that the receiver will specifies that the receiver will
mirror (echo) all received media back mirror (echo) all received media back
to the sender of the RTP stream. to the sender of the RTP stream.
Allowed attribute values: None. Allowed attribute values: None.
14.2 Media Types 14.2 Media Types
The IANA has registered the following media types: The IANA has registered the following media types:
14.2.1 audio/encaprtp 14.2.1 audio/encaprtp
To: ietf-types@iana.org To: ietf-types@iana.org
Subject: Registration of media type audio/encaprtp Subject: Registration of media type audio/encaprtp
Type name: audio Type name: audio
skipping to change at page 23, line 26 skipping to change at page 23, line 30
rate: RTP timestamp clock rate, which is equal to the rate: RTP timestamp clock rate, which is equal to the
sampling rate. The typical rate is 8000; other rates sampling rate. The typical rate is 8000; other rates
may be specified. This is specified by the loop back may be specified. This is specified by the loop back
source, and reflected by the mirror. source, and reflected by the mirror.
Optional parameters: none Optional parameters: none
Encoding considerations: This media type is framed. Encoding considerations: This media type is framed.
Security considerations: See Section 12 of this document. Security considerations: See Section 12 of RFC XXXX.
Interoperability considerations: none Interoperability considerations: none
Published specification: This document. Published specification: RFC XXXX.
Applications which use this media type: Applications wishing Applications which use this media type: Applications wishing
to monitor and ensure the quality of transport to the to monitor and ensure the quality of transport to the
edge of a given VoIP Service. edge of a given VoIP Service.
Additional information: none Additional information: none
Contact: the authors of this document. Contact: the authors of RFC XXXX.
Intended usage: LIMITED USE Intended usage: LIMITED USE
Restrictions on usage: This media type depends on RTP Restrictions on usage: This media type depends on RTP
framing, and hence is only defined for transfer via framing, and hence is only defined for transfer via
RTP. Transfer within other framing protocols is not RTP. Transfer within other framing protocols is not
defined at this time. defined at this time.
Author: Author:
Kaynam Hedayat. Kaynam Hedayat.
Change controller: IETF Audio/Video Transport working Change controller: IETF PAYLOAD working
group delegated from the IESG. group delegated from the IESG.
14.2.2 video/encaprtp 14.2.2 video/encaprtp
To: ietf-types@iana.org To: ietf-types@iana.org
Subject: Registration of media type video/encaprtp Subject: Registration of media type video/encaprtp
Type name: video Type name: video
skipping to change at page 24, line 25 skipping to change at page 24, line 31
Required parameters: Required parameters:
rate: RTP timestamp clock rate, which is equal to the rate: RTP timestamp clock rate, which is equal to the
sampling rate. This is specified by the loop back sampling rate. This is specified by the loop back
source, and reflected by the mirror. source, and reflected by the mirror.
Optional parameters: none Optional parameters: none
Encoding considerations: This media type is framed. Encoding considerations: This media type is framed.
Security considerations: See Section 12 of this document. Security considerations: See Section 12 of RFC XXXX.
Interoperability considerations: none Interoperability considerations: none
Published specification: This document. Published specification: RFC XXXX.
Applications which use this media type: Applications wishing Applications which use this media type: Applications wishing
to monitor and ensure the quality of transport to the to monitor and ensure the quality of transport to the
edge of a given Video Over IP Service. edge of a given Video Over IP Service.
Additional information: none Additional information: none
Contact: the authors of this document. Contact: the authors of RFC XXXX.
Intended usage: LIMITED USE Intended usage: LIMITED USE
Restrictions on usage: This media type depends on RTP Restrictions on usage: This media type depends on RTP
framing, and hence is only defined for transfer via framing, and hence is only defined for transfer via
RTP. Transfer within other framing protocols is not RTP. Transfer within other framing protocols is not
defined at this time. defined at this time.
Author: Author:
Kaynam Hedayat. Kaynam Hedayat.
Change controller: IETF Audio/Video Transport working Change controller: IETF PAYLOAD working
group delegated from the IESG. group delegated from the IESG.
14.2.3 text/encaprtp 14.2.3 text/encaprtp
To: ietf-types@iana.org To: ietf-types@iana.org
Subject: Registration of media type text/encaprtp Subject: Registration of media type text/encaprtp
Type name: text Type name: text
skipping to change at page 25, line 25 skipping to change at page 25, line 30
Required parameters: Required parameters:
rate: RTP timestamp clock rate, which is equal to the rate: RTP timestamp clock rate, which is equal to the
sampling rate. This is specified by the loop back sampling rate. This is specified by the loop back
source, and reflected by the mirror. source, and reflected by the mirror.
Optional parameters: none Optional parameters: none
Encoding considerations: This media type is framed. Encoding considerations: This media type is framed.
Security considerations: See Section 12 of this document. Security considerations: See Section 12 of RFC XXXX.
Interoperability considerations: none Interoperability considerations: none
Published specification: This document. Published specification: RFC XXXX.
Applications which use this media type: Applications wishing Applications which use this media type: Applications wishing
to monitor and ensure the quality of transport to the to monitor and ensure the quality of transport to the
edge of a given Real-Time Text Service. edge of a given Real-Time Text Service.
Additional information: none Additional information: none
Contact: the authors of this document. Contact: the authors of RFC XXXX.
Intended usage: LIMITED USE Intended usage: LIMITED USE
Restrictions on usage: This media type depends on RTP Restrictions on usage: This media type depends on RTP
framing, and hence is only defined for transfer via framing, and hence is only defined for transfer via
RTP. Transfer within other framing protocols is not RTP. Transfer within other framing protocols is not
defined at this time. defined at this time.
Author: Author:
Kaynam Hedayat. Kaynam Hedayat.
Change controller: IETF Audio/Video Transport working Change controller: IETF PAYLOAD working
group delegated from the IESG. group delegated from the IESG.
14.2.4 application/encaprtp 14.2.4 application/encaprtp
To: ietf-types@iana.org To: ietf-types@iana.org
Subject: Registration of media type Subject: Registration of media type
application/encaprtp application/encaprtp
Type name: application Type name: application
skipping to change at page 26, line 26 skipping to change at page 26, line 29
Required parameters: Required parameters:
rate: RTP timestamp clock rate, which is equal to the rate: RTP timestamp clock rate, which is equal to the
sampling rate. This is specified by the loop back sampling rate. This is specified by the loop back
source, and reflected by the mirror. source, and reflected by the mirror.
Optional parameters: none Optional parameters: none
Encoding considerations: This media type is framed. Encoding considerations: This media type is framed.
Security considerations: See Section 12 of this document. Security considerations: See Section 12 of RFC XXXX.
Interoperability considerations: none Interoperability considerations: none
Published specification: This document. Published specification: RFC XXXX.
Applications which use this media type: Applications wishing Applications which use this media type: Applications wishing
to monitor and ensure the quality of transport to the to monitor and ensure the quality of transport to the
edge of a given Real-Time Application Service. edge of a given Real-Time Application Service.
Additional information: none Additional information: none
Contact: the authors of this document. Contact: the authors of RFC XXXX.
Intended usage: LIMITED USE Intended usage: LIMITED USE
Restrictions on usage: This media type depends on RTP Restrictions on usage: This media type depends on RTP
framing, and hence is only defined for transfer via framing, and hence is only defined for transfer via
RTP. Transfer within other framing protocols is not RTP. Transfer within other framing protocols is not
defined at this time. defined at this time.
Author: Author:
Kaynam Hedayat. Kaynam Hedayat.
Change controller: IETF Audio/Video Transport working Change controller: IETF PAYLOAD working
group delegated from the IESG. group delegated from the IESG.
14.2.5 audio/rtploopback 14.2.5 audio/rtploopback
To: ietf-types@iana.org To: ietf-types@iana.org
Subject: Registration of media type audio/rtploopback Subject: Registration of media type audio/rtploopback
Type name: audio Type name: audio
skipping to change at page 27, line 26 skipping to change at page 27, line 29
rate:RTP timestamp clock rate, which is equal to the rate:RTP timestamp clock rate, which is equal to the
sampling rate. The typical rate is 8000; other rates sampling rate. The typical rate is 8000; other rates
may be specified. This is specified by the loop back may be specified. This is specified by the loop back
source, and reflected by the mirror. source, and reflected by the mirror.
Optional parameters: none Optional parameters: none
Encoding considerations: This media type is framed. Encoding considerations: This media type is framed.
Security considerations: See Section 12 of this document. Security considerations: See Section 12 of RFC XXXX.
Interoperability considerations: none Interoperability considerations: none
Published specification: This document. Published specification: RFC XXXX.
Applications which use this media type: Applications wishing Applications which use this media type: Applications wishing
to monitor and ensure the quality of transport to the to monitor and ensure the quality of transport to the
edge of a given VoIP Service. edge of a given VoIP Service.
Additional information: none Additional information: none
Contact: the authors of this document. Contact: the authors of RFC XXXX.
Intended usage: LIMITED USE Intended usage: LIMITED USE
Restrictions on usage: This media type depends on RTP Restrictions on usage: This media type depends on RTP
framing, and hence is only defined for transfer via framing, and hence is only defined for transfer via
RTP. Transfer within other framing protocols is not RTP. Transfer within other framing protocols is not
defined at this time. defined at this time.
Author: Author:
Kaynam Hedayat. Kaynam Hedayat.
Change controller: IETF Audio/Video Transport working Change controller: IETF PAYLOAD working
group delegated from the IESG. group delegated from the IESG.
14.2.6 video/rtploopback 14.2.6 video/rtploopback
To: ietf-types@iana.org To: ietf-types@iana.org
Subject: Registration of media type video/rtploopback Subject: Registration of media type video/rtploopback
Type name: video Type name: video
skipping to change at page 28, line 25 skipping to change at page 28, line 28
Required parameters: Required parameters:
rate:RTP timestamp clock rate, which is equal to the rate:RTP timestamp clock rate, which is equal to the
sampling rate. This is specified by the loop back sampling rate. This is specified by the loop back
source, and reflected by the mirror. source, and reflected by the mirror.
Optional parameters: none Optional parameters: none
Encoding considerations: This media type is framed. Encoding considerations: This media type is framed.
Security considerations: See Section 12 of this document. Security considerations: See Section 12 of RFC XXXX.
Interoperability considerations: none Interoperability considerations: none
Published specification: This document. Published specification: RFC XXXX.
Applications which use this media type: Applications wishing Applications which use this media type: Applications wishing
to monitor and ensure the quality of transport to the to monitor and ensure the quality of transport to the
edge of a given Video Over IP Service. edge of a given Video Over IP Service.
Additional information: none Additional information: none
Contact: the authors of this document. Contact: the authors of RFC XXXX.
Intended usage: LIMITED USE Intended usage: LIMITED USE
Restrictions on usage: This media type depends on RTP Restrictions on usage: This media type depends on RTP
framing, and hence is only defined for transfer via framing, and hence is only defined for transfer via
RTP. Transfer within other framing protocols is not RTP. Transfer within other framing protocols is not
defined at this time. defined at this time.
Author: Author:
Kaynam Hedayat. Kaynam Hedayat.
Change controller: IETF Audio/Video Transport working Change controller: IETF PAYLOAD working
group delegated from the IESG. group delegated from the IESG.
14.2.7 text/rtploopback 14.2.7 text/rtploopback
To: ietf-types@iana.org To: ietf-types@iana.org
Subject: Registration of media type text/rtploopback Subject: Registration of media type text/rtploopback
Type name: text Type name: text
skipping to change at page 29, line 25 skipping to change at page 29, line 25
Required parameters: Required parameters:
rate:RTP timestamp clock rate, which is equal to the rate:RTP timestamp clock rate, which is equal to the
sampling rate. This is specified by the loop back sampling rate. This is specified by the loop back
source, and reflected by the mirror. source, and reflected by the mirror.
Optional parameters: none Optional parameters: none
Encoding considerations: This media type is framed. Encoding considerations: This media type is framed.
Security considerations: See Section 12 of this document. Security considerations: See Section 12 of RFC XXXX.
Interoperability considerations: none Interoperability considerations: none
Published specification: This document. Published specification: RFC XXXX.
Applications which use this media type: Applications wishing Applications which use this media type: Applications wishing
to monitor and ensure the quality of transport to the to monitor and ensure the quality of transport to the
edge of a given Real-Time Text Service. edge of a given Real-Time Text Service.
Additional information: none Additional information: none
Contact: the authors of this document. Contact: the authors of RFC XXXX.
Intended usage: LIMITED USE Intended usage: LIMITED USE
Restrictions on usage: This media type depends on RTP Restrictions on usage: This media type depends on RTP
framing, and hence is only defined for transfer via framing, and hence is only defined for transfer via
RTP. Transfer within other framing protocols is not RTP. Transfer within other framing protocols is not
defined at this time. defined at this time.
Author: Author:
Kaynam Hedayat. Kaynam Hedayat.
Change controller: IETF Audio/Video Transport working Change controller: IETF PAYLOAD working
group delegated from the IESG. group delegated from the IESG.
14.2.8 application/rtploopback 14.2.8 application/rtploopback
To: ietf-types@iana.org To: ietf-types@iana.org
Subject: Registration of media type Subject: Registration of media type
application/rtploopback application/rtploopback
Type name: application Type name: application
skipping to change at page 30, line 26 skipping to change at page 30, line 26
Required parameters: Required parameters:
rate:RTP timestamp clock rate, which is equal to the rate:RTP timestamp clock rate, which is equal to the
sampling rate. This is specified by the loop back sampling rate. This is specified by the loop back
source, and reflected by the mirror. source, and reflected by the mirror.
Optional parameters: none Optional parameters: none
Encoding considerations: This media type is framed. Encoding considerations: This media type is framed.
Security considerations: See Section 12 of this document. Security considerations: See Section 12 of RFC XXXX.
Interoperability considerations: none Interoperability considerations: none
Published specification: This document. Published specification: RFC XXXX.
Applications which use this media type: Applications wishing Applications which use this media type: Applications wishing
to monitor and ensure the quality of transport to the to monitor and ensure the quality of transport to the
edge of a given Real-Time Application Service. edge of a given Real-Time Application Service.
Additional information: none Additional information: none
Contact: the authors of this document. Contact: the authors of RFC XXXX.
Intended usage: LIMITED USE Intended usage: LIMITED USE
Restrictions on usage: This media type depends on RTP Restrictions on usage: This media type depends on RTP
framing, and hence is only defined for transfer via framing, and hence is only defined for transfer via
RTP. Transfer within other framing protocols is not RTP. Transfer within other framing protocols is not
defined at this time. defined at this time.
Author: Author:
Kaynam Hedayat. Kaynam Hedayat.
Change controller: IETF Audio/Video Transport working Change controller: IETF PAYLOAD working
group delegated from the IESG. group delegated from the IESG.
15. Acknowledgements 15. Acknowledgements
This document's editor would like to thank the original authors of This document's editor would like to thank the original authors of
the document: Kaynam Hedayat, Nagarjuna Venna, Paul E. Jones, Arjun the document: Kaynam Hedayat, Nagarjuna Venna, Paul E. Jones, Arjun
Roychowdhury, Chelliah SivaChelvan, and Nathan Stratton. The Roychowdhury, Chelliah SivaChelvan, and Nathan Stratton. The
editor has made fairly insignificant changes in the end. Also, editor has made fairly insignificant changes in the end. Also,
we'd like to thank Magnus Westerlund, Miguel Garcia, Muthu we'd like to thank Magnus Westerlund, Miguel Garcia, Muthu Arul
Arul Mozhi Perumal, Jeff Bernstein, Paul Kyzivat, Dave Oran, Mozhi Perumal, Jeff Bernstein, Paul Kyzivat, Dave Oran, Flemming
Flemming Andreasen, Gunnar Hellstrom, Emil Ivov and Dan Wing for Andreasen, Gunnar Hellstrom, Emil Ivov and Dan Wing for their
their feedback, comments and suggestions. feedback, comments and suggestions.
16. Normative References 16. Normative References
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer
Model with the Session Description Protocol (SDP)", Model with the Session Description Protocol (SDP)",
RFC 3264, June 2002. RFC 3264, June 2002.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R. and V. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R. and V.
Jacobson, "RTP: A Transport Protocol for Real-Time Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003. Applications", STD 64, RFC 3550, July 2003.
[RFC3611] Almeroth, K., Caceres, R., Clark, A., Cole, R., [RFC3611] Almeroth, K., Caceres, R., Clark, A., Cole, R.,
skipping to change at page 32, line 8 skipping to change at page 32, line 8
[RFC3551] Schulzrinne, H., Casner, S., "RTP Profile for Audio [RFC3551] Schulzrinne, H., Casner, S., "RTP Profile for Audio
and Video Conferences with Minimial Control", STD 65, and Video Conferences with Minimial Control", STD 65,
RFC 3551, July 2003. RFC 3551, July 2003.
[RFC4566] Handley, M., Jacobson, V., Perkins, C., "SDP: Session [RFC4566] Handley, M., Jacobson, V., Perkins, C., "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[RFC4855] Casner, S., "Media Type Registration of RTP Payload [RFC4855] Casner, S., "Media Type Registration of RTP Payload
Formats", RFC 4855, February 2007. Formats", RFC 4855, February 2007.
17. Informative References 17. Informative References
[RFC5245] Rosenberg, J., "Interactive Connectivity [RFC5245] Rosenberg, J., "Interactive Connectivity
Establishment (ICE): A Protocol for Network Address Establishment (ICE): A Protocol for Network Address
Translator (NAT) Traversal for Offer/Answer Translator (NAT) Traversal for Offer/Answer
Protocols", RFC 5245, April 2010. Protocols", RFC 5245, April 2010.
[RFC6263] Marjou, X., Sollaud, A., "Application Mechanism for [RFC6263] Marjou, X., Sollaud, A., "Application Mechanism for
Keeping Alive the NAT Mappings Associated with RTP / Keeping Alive the NAT Mappings Associated with RTP /
RTP Control Protocol (RTCP) Flows", RFC 6263, June RTP Control Protocol (RTCP) Flows", RFC 6263, June
2011. 2011.
 End of changes. 83 change blocks. 
93 lines changed or deleted 108 lines changed or added

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