draft-ietf-avtext-sdes-hdr-ext-03.txt   draft-ietf-avtext-sdes-hdr-ext-04.txt 
Network Working Group M. Westerlund Network Working Group M. Westerlund
Internet-Draft B. Burman Internet-Draft B. Burman
Intended status: Standards Track Ericsson Intended status: Standards Track Ericsson
Expires: August 18, 2016 R. Even Expires: August 25, 2016 R. Even
Huawei Technologies Huawei Technologies
M. Zanaty M. Zanaty
Cisco Systems Cisco Systems
February 15, 2016 February 22, 2016
RTP Header Extension for RTCP Source Description Items RTP Header Extension for RTCP Source Description Items
draft-ietf-avtext-sdes-hdr-ext-03 draft-ietf-avtext-sdes-hdr-ext-04
Abstract Abstract
Source Description (SDES) items are normally transported in RTP Source Description (SDES) items are normally transported in RTP
control protocol (RTCP). In some cases it can be beneficial to speed control protocol (RTCP). In some cases it can be beneficial to speed
up the delivery of these items. Mainly when a new source (SSRC) up the delivery of these items. Mainly when a new source (SSRC)
joins an RTP session and the receivers needs this source's identity, joins an RTP session and the receivers needs this source's identity,
relation to other sources, or its synchronization context, all of relation to other sources, or its synchronization context, all of
which may be fully or partially identified using SDES items. To which may be fully or partially identified using SDES items. To
enable this optimization, this document specifies a new RTP header enable this optimization, this document specifies a new RTP header
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 18, 2016. This Internet-Draft will expire on August 25, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 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
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4.1.2. Two-Byte Format . . . . . . . . . . . . . . . . . . . 5 4.1.2. Two-Byte Format . . . . . . . . . . . . . . . . . . . 5
4.2. Usage of the SDES Item Header Extension . . . . . . . . . 6 4.2. Usage of the SDES Item Header Extension . . . . . . . . . 6
4.2.1. One or Two Byte Headers . . . . . . . . . . . . . . . 6 4.2.1. One or Two Byte Headers . . . . . . . . . . . . . . . 6
4.2.2. MTU and Packet Expansion . . . . . . . . . . . . . . 7 4.2.2. MTU and Packet Expansion . . . . . . . . . . . . . . 7
4.2.3. Transmission Considerations . . . . . . . . . . . . . 7 4.2.3. Transmission Considerations . . . . . . . . . . . . . 7
4.2.4. Different Usages . . . . . . . . . . . . . . . . . . 9 4.2.4. Different Usages . . . . . . . . . . . . . . . . . . 9
4.2.5. SDES Items in RTCP . . . . . . . . . . . . . . . . . 9 4.2.5. SDES Items in RTCP . . . . . . . . . . . . . . . . . 9
4.2.6. Update Flaps . . . . . . . . . . . . . . . . . . . . 10 4.2.6. Update Flaps . . . . . . . . . . . . . . . . . . . . 10
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5.1. Reservation of the SDES URN sub-space . . . . . . . . . . 11 5.1. Reservation of the SDES URN sub-space . . . . . . . . . . 11
5.2. Registration of SDES Items . . . . . . . . . . . . . . . 11 5.2. Registration of SDES Items . . . . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative References . . . . . . . . . . . . . . . . . . 13 8.1. Normative References . . . . . . . . . . . . . . . . . . 13
8.2. Informative References . . . . . . . . . . . . . . . . . 13 8.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
This specification defines an RTP header extension [RFC3550][RFC5285] This specification defines an RTP header extension [RFC3550][RFC5285]
that can carry RTCP source description (SDES) items. By including that can carry RTCP source description (SDES) items. By including
selected SDES items in a header extension the determination of selected SDES items in a header extension the determination of
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packet with the updated value. The second reason is the different packet with the updated value. The second reason is the different
code-paths for RTP and RTCP in implementations. An update to the code-paths for RTP and RTCP in implementations. An update to the
sender's SDES item parameter can take a different time to propagate sender's SDES item parameter can take a different time to propagate
to the receiver than the corresponding media data. For example, an to the receiver than the corresponding media data. For example, an
RTCP packet with the SDES item included that may have been generated RTCP packet with the SDES item included that may have been generated
prior to the update can still reside in a buffer and be sent prior to the update can still reside in a buffer and be sent
unmodified. The update of the item's value can at the same time unmodified. The update of the item's value can at the same time
cause RTP packets to be sent including the header extension, prior to cause RTP packets to be sent including the header extension, prior to
the RTCP packet being sent. the RTCP packet being sent.
However, most of these issues can be avoided in the receiver by However, most of these issues can be avoided by the receiver
performing some checks before updating the receiver's stored value. performing some checks before updating the receiver's stored value.
To handle flaps caused by reordering, only SDES items received in RTP To handle flaps caused by reordering, only SDES items received in RTP
packets with a higher extended sequence number than the last change packets with a higher extended sequence number than the last change
shall be applied, i.e. discard items that can be determined to be shall be applied, i.e. discard items that can be determined to be
older than the current one. For compound RTCP packets, which will older than the current one. For compound RTCP packets, which will
contain an Sender Report (SR) packet (assuming an active RTP sender), contain an Sender Report (SR) packet (assuming an active RTP sender),
the receiver can use the RTCP SR Timestamp field to determine at what the receiver can use the RTCP SR Timestamp field to determine at what
approximate time it was transmitted. If the timestamp is earlier approximate time it was transmitted. If the timestamp is earlier
than the last received RTP packet with a header extension carrying an than the last received RTP packet with a header extension carrying an
SDES item, and especially if carrying a previously used value, the SDES item, and especially if carrying a previously used value, the
SDES item in the RTCP SDES packet can be ignored. Note that media SDES item in the RTCP SDES packet can be ignored. Note that media
processing and transmission pacing can easily cause the RTP header processing and transmission pacing can easily cause the RTP header
timestamp field as well as the RTCP SR timestamp field to not match timestamp field as well as the RTCP SR timestamp field to not match
with the actual transmission time. with the actual transmission time.
5. IANA Considerations 5. IANA Considerations
This section makes the following requests to IANA: This section makes the following requests to IANA:
o Register and reserve for SDES items the URN sub-space o Create a new sub-registry reserved for RTCP SDES items with the
"urn:ietf:params:rtp-hdrext:sdes:" in the RTP Compact Header URN sub-space "urn:ietf:params:rtp-hdrext:sdes:" in the RTP
Extensions registry. Compact Header Extensions registry.
o Register the SDES items appropriate for use with the RTP header o Register the SDES items appropriate for use with the RTP header
extension defined in this document. extension defined in this document.
5.1. Reservation of the SDES URN sub-space 5.1. Reservation of the SDES URN sub-space
The reason to require registering a URN within an SDES sub-space is The reason to require registering a URN within an SDES sub-space is
that the name represents an RTCP Source Description item, where a that the name represents an RTCP Source Description item, where a
specification is strongly recommended. The formal policy is specification is strongly recommended [RFC3550]. The formal policy
maintained from the main space, as specified by [RFC5285], i.e. MUST be maintained from the main space, as specified by [RFC5285],
Expert Review. However, the following additional items need to be i.e. Expert Review. However, the following additional items need to
considered when applying for a registration within this sub-space of be considered when applying for a registration within this sub-space
the RTP Compact Header Extensions registry: of the RTP Compact Header Extensions registry:
o Any registration using an Extension URI that starts with o Any registration using an Extension URI that starts with
"urn:ietf:params:rtp-hdrext:sdes:" MUST also have a registered "urn:ietf:params:rtp-hdrext:sdes:" MUST also have a registered
Source Description item in the "RTP SDES item types" registry. Source Description item in the "RTP SDES item types" registry.
o Secondly, a security and privacy consideration for the SDES item o Secondly, a security and privacy consideration for the SDES item
must be provided with the registration. MUST be provided with the registration.
o Thirdly, information must be provided on why this SDES item o Thirdly, information MUST be provided on why this SDES item
requires timely delivery, motivating it to be transported in a requires timely delivery, motivating it to be transported in a
header extension rather than as RTCP only. header extension rather than as RTCP only.
IANA is requested to register the below in the RTP Compact Header IANA is requested to register the below in the RTP Compact Header
Extensions: Extensions, and to create the corresponding sub-registry:
Name: RTP SDES Compact Header Extensions
Extension URI: urn:ietf:params:rtp-hdrext:sdes Extension URI: urn:ietf:params:rtp-hdrext:sdes
Description: Reserved as base URN for SDES items that are also Description: Reserved as base URN for RTP SDES items that are also
defined as RTP Compact header extensions. defined as RTP Compact header extensions.
Contact: Authors of [RFCXXXX] Contact: Authors of [RFCXXXX]
Reference: [RFCXXXX] Reference: [RFCXXXX]
RFC-editor note: Please replace all occurrences of RFCXXXX with the RFC-editor note: Please replace all occurrences of RFCXXXX with the
RFC number this specification receives when published. RFC number this specification receives when published.
The formal reference for registrations in the RTP SDES Compact Header
Extensions registry is the RFC number of the RFC documenting the
extension.
5.2. Registration of SDES Items 5.2. Registration of SDES Items
It is requested that the following SDES item is registered in the RTP It is requested that the following SDES item is registered in the
Compact Header Extensions registry: newly formed RTP SDES Compact Header Extensions registry:
Extension URI: urn:ietf:params:rtp-hdrext:sdes:cname Extension URI: urn:ietf:params:rtp-hdrext:sdes:cname
Description: Source Description: Canonical End-Point Identifier Description: Source Description: Canonical End-Point Identifier
(SDES CNAME) (SDES CNAME)
Contact: Authors of [RFCXXXX] Contact: Authors of [RFCXXXX]
Reference: [RFCXXXX] Reference: [RFCXXXX]
We also note that the MID SDES item is already registered in the RFC-editor note: Please move the MID SDES item already registered in
registry by [I-D.ietf-mmusic-sdp-bundle-negotiation]. the main registry by [I-D.ietf-mmusic-sdp-bundle-negotiation] to the
newly formed RTP SDES Compact Header Extensions.
6. Security Considerations 6. Security Considerations
Source Description items may contain data that are sensitive from a Source Description items may contain data that are sensitive from a
security perspective. There are SDES items that are or may be security perspective. There are SDES items that are or may be
sensitive from a user privacy perspective, like CNAME, NAME, EMAIL, sensitive from a user privacy perspective, like CNAME, NAME, EMAIL,
PHONE, LOC and H323-CADDR. Some may contain sensitive information, PHONE, LOC and H323-CADDR. Some may contain sensitive information,
like NOTE and PRIV, while others may be sensitive from profiling like NOTE and PRIV, while others may be sensitive from profiling
implementations for vulnerability or other reasons, like TOOL. The implementations for vulnerability or other reasons, like TOOL. The
CNAME sensitivity can vary depending on how it is generated and what CNAME sensitivity can vary depending on how it is generated and what
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Real-time Transport Protocol (SRTP)", RFC 6904, Real-time Transport Protocol (SRTP)", RFC 6904,
DOI 10.17487/RFC6904, April 2013, DOI 10.17487/RFC6904, April 2013,
<http://www.rfc-editor.org/info/rfc6904>. <http://www.rfc-editor.org/info/rfc6904>.
8.2. Informative References 8.2. Informative References
[I-D.ietf-mmusic-sdp-bundle-negotiation] [I-D.ietf-mmusic-sdp-bundle-negotiation]
Holmberg, C., Alvestrand, H., and C. Jennings, Holmberg, C., Alvestrand, H., and C. Jennings,
"Negotiating Media Multiplexing Using the Session "Negotiating Media Multiplexing Using the Session
Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle-
negotiation-25 (work in progress), January 2016. negotiation-26 (work in progress), February 2016.
[RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed., [RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed.,
"RTP Control Protocol Extended Reports (RTCP XR)", "RTP Control Protocol Extended Reports (RTCP XR)",
RFC 3611, DOI 10.17487/RFC3611, November 2003, RFC 3611, DOI 10.17487/RFC3611, November 2003,
<http://www.rfc-editor.org/info/rfc3611>. <http://www.rfc-editor.org/info/rfc3611>.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566, Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <http://www.rfc-editor.org/info/rfc4566>. July 2006, <http://www.rfc-editor.org/info/rfc4566>.
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