draft-ietf-mmusic-duplication-grouping-04.txt   rfc7104.txt 
MMUSIC A. Begen Internet Engineering Task Force (IETF) A. Begen
Internet-Draft Cisco Request for Comments: 7104 Cisco
Intended status: Standards Track Y. Cai Category: Standards Track Y. Cai
Expires: May 25, 2014 Microsoft ISSN: 2070-1721 Microsoft
H. Ou H. Ou
Cisco Cisco
November 21, 2013 January 2014
Duplication Grouping Semantics in the Session Description Protocol Duplication Grouping Semantics in the Session Description Protocol
draft-ietf-mmusic-duplication-grouping-04
Abstract Abstract
Packet loss is undesirable for real-time multimedia sessions, but can Packet loss is undesirable for real-time multimedia sessions, but it
occur due to congestion, or other unplanned network outages. This is can occur due to congestion or other unplanned network outages. This
especially true for IP multicast networks, where packet loss patterns is especially true for IP multicast networks, where packet loss
can vary greatly between receivers. One technique that can be used patterns can vary greatly between receivers. One technique that can
to recover from packet loss without incurring unbounded delay for all be used to recover from packet loss without incurring unbounded delay
the receivers is to duplicate the packets and send them in separate for all the receivers is to duplicate the packets and send them in
redundant streams. This document defines the semantics for grouping separate redundant streams. This document defines the semantics for
redundant streams in the Session Description Protocol (SDP). The grouping redundant streams in the Session Description Protocol (SDP).
semantics defined in this document are to be used with the SDP The semantics defined in this document are to be used with the SDP
Grouping Framework. SSRC-level (Synchronization Source) grouping Grouping Framework. Grouping semantics at the Synchronization Source
semantics are also defined in this document for RTP streams using (SSRC) level are also defined in this document for RTP streams using
SSRC multiplexing. SSRC multiplexing.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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 http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on May 25, 2014. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7104.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction ....................................................2
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Notation ...........................................3
3. Duplication Grouping . . . . . . . . . . . . . . . . . . . . 3 3. Duplication Grouping ............................................3
3.1. "DUP" Grouping Semantics . . . . . . . . . . . . . . . . 3 3.1. "DUP" Grouping Semantics ...................................3
3.2. Duplication Grouping for SSRC-Multiplexed RTP Streams . . 3 3.2. Duplication Grouping for SSRC-Multiplexed RTP Streams ......3
3.3. SDP Offer/Answer Model Considerations . . . . . . . . . . 4 3.3. SDP Offer/Answer Model Considerations ......................4
4. SDP Examples . . . . . . . . . . . . . . . . . . . . . . . . 4 4. SDP Examples ....................................................5
4.1. Separate Source Addresses . . . . . . . . . . . . . . . . 4 4.1. Separate Source Addresses ..................................5
4.2. Separate Destination Addresses . . . . . . . . . . . . . 5 4.2. Separate Destination Addresses .............................6
4.3. Temporal Redundancy . . . . . . . . . . . . . . . . . . . 6 4.3. Temporal Redundancy ........................................7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations .........................................7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations .............................................8
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgments .................................................8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 8. References ......................................................8
8.1. Normative References . . . . . . . . . . . . . . . . . . 7 8.1. Normative References .......................................8
8.2. Informative References . . . . . . . . . . . . . . . . . 7 8.2. Informative References .....................................9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
The Real-time Transport Protocol (RTP) [RFC3550] is widely used today The Real-time Transport Protocol (RTP) [RFC3550] is widely used today
for delivering IPTV traffic, and other real-time multimedia sessions. for delivering IPTV traffic and other real-time multimedia sessions.
Many of these applications support very large numbers of receivers, Many of these applications support very large numbers of receivers
and rely on intra-domain UDP/IP multicast for efficient distribution and rely on intra-domain UDP/IP multicast for efficient distribution
of traffic within the network. of traffic within the network.
While this combination has proved successful, there does exist a While this combination has proved successful, there does exist a
weakness. As [RFC2354] noted, packet loss is not avoidable, even in weakness. As [RFC2354] noted, packet loss is not avoidable, even in
a carefully managed network. This loss might be due to congestion, a carefully managed network. This loss might be due to congestion;
it might also be a result of an unplanned outage caused by a flapping it might also be a result of an unplanned outage caused by a flapping
link, link or interface failure, a software bug, or a maintenance link, a link or interface failure, a software bug, or a maintenance
person accidentally cutting the wrong fiber. Since UDP/IP flows do person accidentally cutting the wrong fiber. Since UDP/IP flows do
not provide any means for detecting loss and retransmitting packets, not provide any means for detecting loss and retransmitting packets,
it leaves up to the RTP layer and the applications to detect, and it is left up to the RTP layer and the applications to detect, and
recover from, packet loss. recover from, packet loss.
One technique to recover from packet loss without incurring unbounded One technique to recover from packet loss without incurring unbounded
delay for all the receivers is to duplicate the packets and send them delay for all the receivers is to duplicate the packets and send them
in separate redundant streams. Variations on this idea have been in separate redundant streams. Variations on this idea have been
implemented and deployed today [IC2011]. implemented and deployed today [IC2011]. [RTP-DUP] explains how
[I-D.ietf-avtext-rtp-duplication] explains how duplication can be duplication can be achieved for RTP streams without breaking the RTP
achieved for RTP streams without breaking the RTP and RTP Control and RTP Control Protocol (RTCP) functionality. In this document, we
Protocol (RTCP) functionality. In this document, we describe the describe the semantics needed in the Session Description Protocol
semantics needed in the Session Description Protocol (SDP) [RFC4566] (SDP) [RFC4566] to support this technique.
to support this technique.
2. Requirements Notation 2. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. [RFC2119].
3. Duplication Grouping 3. Duplication Grouping
3.1. "DUP" Grouping Semantics 3.1. "DUP" Grouping Semantics
Each "a=group" line is used to indicate an association relationship Each "a=group" line is used to indicate an association relationship
between the redundant streams. The streams included in one "a=group" between the redundant streams. The streams included in one "a=group"
line are called a Duplication Group. line are called a "Duplication Group".
Using the SDP Grouping Framework in [RFC5888], this document defines Using the SDP Grouping Framework in [RFC5888], this document defines
"DUP" as the grouping semantics for redundant streams. "DUP" as the grouping semantics for redundant streams.
The "a=group:DUP" semantics MUST be used to group the redundant The "a=group:DUP" semantics MUST be used to group the redundant
streams except when the streams are specified in the same media streams, except when the streams are specified in the same media
description, i.e., in the same "m" line (See Section 3.2). In an description, i.e., in the same "m" line (see Section 3.2). In an
"a=group:DUP" line, the order of the listed redundant streams does "a=group:DUP" line, the order of the listed redundant streams does
not strictly indicate the order of transmission, although it is not strictly indicate the order of transmission, although it is
RECOMMENDED that the stream listed first is sent first, with the RECOMMENDED that the stream listed first be sent first, with the
other stream(s) being the (time-delayed) duplicate(s). other stream(s) being the (time-delayed) duplicate(s).
3.2. Duplication Grouping for SSRC-Multiplexed RTP Streams 3.2. Duplication Grouping for SSRC-Multiplexed RTP Streams
[RFC5576] defines an SDP media-level attribute, called 'ssrc-group', [RFC5576] defines an SDP media-level attribute, called "ssrc-group",
for grouping the RTP streams that are SSRC multiplexed and carried in for grouping the RTP streams that are SSRC multiplexed and carried in
the same RTP session. The grouping is based on the SSRC identifiers. the same RTP session. The grouping is based on the SSRC identifiers.
Since SSRC-multiplexed RTP streams are defined in the same "m" line, Since SSRC-multiplexed RTP streams are defined in the same "m" line,
the 'group' attribute cannot be used. the "group" attribute cannot be used.
This section explains how duplication is used with SSRC-multiplexed This section explains how duplication is used with SSRC-multiplexed
streams using the 'ssrc-group' attribute [RFC5576]. streams using the "ssrc-group" attribute [RFC5576].
The semantics of "DUP" for the 'ssrc-group' attribute are the same as The semantics of "DUP" for the "ssrc-group" attribute are the same as
the one defined for the 'group' attribute except that the SSRC the one defined for the "group" attribute, except that the SSRC
identifiers are used to designate the duplication grouping identifiers are used to designate the duplication grouping
associations: a=ssrc-group:DUP *(SP ssrc-id) [RFC5576]. As above, associations: a=ssrc-group:DUP *(SP ssrc-id) [RFC5576]. As above,
while in an "a=ssrc-group:DUP" line, the order of the listed while in an "a=ssrc-group:DUP" line, the order of the listed
redundant streams does not necessarily indicate the order of redundant streams does not necessarily indicate the order of
transmission, it is RECOMMENDED that the stream listed first is sent transmission, but it is RECOMMENDED that the stream listed first be
first, with the other stream(s) being the (time-delayed) sent first, with the other stream(s) being the (time-delayed)
duplicate(s). duplicate(s).
3.3. SDP Offer/Answer Model Considerations 3.3. SDP Offer/Answer Model Considerations
When offering duplication grouping using SDP in an Offer/Answer model When offering duplication grouping using SDP in an offer/answer model
[RFC3264], the following considerations apply. [RFC3264], the following considerations apply.
A node that is receiving an offer from a sender may or may not A node that is receiving an offer from a sender may or may not
understand line grouping. It is also possible that the node understand line grouping. It is also possible that the node
understands line grouping but it does not understand the "DUP" understands line grouping but does not understand the "DUP"
semantics. From the viewpoint of the sender of the offer, these semantics. From the viewpoint of the sender of the offer, these
cases are indistinguishable. cases are indistinguishable.
When a node is offered a session with the "DUP" grouping semantics When a node is offered a session with the "DUP" grouping semantics
but it does not support line grouping or the duplication grouping but it does not support line grouping or the duplication grouping
semantics, as per [RFC5888], the node responds to the offer either semantics, as per [RFC5888], the node responds to the offer either
(1) with an answer that omits the grouping attribute or (2) with a (1) with an answer that omits the grouping attribute or (2) with a
refusal to the request (e.g., 488 Not Acceptable Here or 606 Not refusal to the request (e.g., "488 Not Acceptable Here" or "606 Not
Acceptable in SIP). Acceptable in SIP").
In the first case, the original sender of the offer must send a new In the first case, the original sender of the offer must send a new
offer without any duplication grouping. In the second case, if the offer without any duplication grouping. In the second case, if the
sender of the offer still wishes to establish the session, it should sender of the offer still wishes to establish the session, it should
retry the request with an offer without the duplication grouping. retry the request with an offer without the duplication grouping.
This behavior is specified in [RFC5888]. This behavior is specified in [RFC5888].
4. SDP Examples 4. SDP Examples
4.1. Separate Source Addresses 4.1. Separate Source Addresses
In this example, the redundant streams use the same IP destination In this example, the redundant streams use the same IP destination
address (232.252.0.1) but they are sourced from different addresses address (232.252.0.1), but they are sourced from different addresses
(198.51.100.1 and 198.51.100.2). Thus, the receiving host needs to (198.51.100.1 and 198.51.100.2). Thus, the receiving host needs to
join both source-specific multicast (SSM) sessions separately. join both source-specific multicast (SSM) sessions separately.
v=0 v=0
o=ali 1122334455 1122334466 IN IP4 dup.example.com o=ali 1122334455 1122334466 IN IP4 dup.example.com
s=DUP Grouping Semantics s=DUP Grouping Semantics
t=0 0 t=0 0
m=video 30000 RTP/AVP 100 m=video 30000 RTP/AVP 100
c=IN IP4 233.252.0.1/127 c=IN IP4 233.252.0.1/127
a=source-filter:incl IN IP4 233.252.0.1 198.51.100.1 198.51.100.2 a=source-filter:incl IN IP4 233.252.0.1 198.51.100.1 198.51.100.2
a=rtpmap:100 MP2T/90000 a=rtpmap:100 MP2T/90000
a=ssrc:1000 cname:ch1@example.com a=ssrc:1000 cname:ch1@example.com
a=ssrc:1010 cname:ch1@example.com a=ssrc:1010 cname:ch1@example.com
a=ssrc-group:DUP 1000 1010 a=ssrc-group:DUP 1000 1010
a=mid:Ch1 a=mid:Ch1
Note that in actual use, SSRC values, which are random 32-bit Note that in actual use, SSRC values, which are random 32-bit
numbers, can be much larger than the ones shown in this example. numbers, can be much larger than the ones shown in this example.
Also note that this SDP description does not use the 'duplication- Also, note that this SDP description does not use the "duplication-
delay' attribute (defined in [I-D.ietf-mmusic-delayed-duplication]) delay" attribute (defined in [DELAYED-DUP]) since the sender does not
since the sender does not apply any delay between the redundant apply any delay between the redundant streams upon transmission.
streams upon transmission. Alternatively, one MAY explicitly insert Alternatively, one MAY explicitly insert an "a=duplication-delay:0"
an "a=duplication-delay:0" line before the "a=mid:Ch1" line for line before the "a=mid:Ch1" line for informational purposes.
informational purposes.
4.2. Separate Destination Addresses 4.2. Separate Destination Addresses
In this example, the redundant streams have different IP destination In this example, the redundant streams have different IP destination
addresses. The example shows the same UDP port number and IP source addresses. The example shows the same UDP port number and IP source
address for each stream, but either or both could have been different address for each stream, but either or both could have been different
for the two streams. for the two streams.
v=0 v=0
o=ali 1122334455 1122334466 IN IP4 dup.example.com o=ali 1122334455 1122334466 IN IP4 dup.example.com
s=DUP Grouping Semantics s=DUP Grouping Semantics
t=0 0 t=0 0
a=group:DUP S1a S1b a=group:DUP S1a S1b
m=video 30000 RTP/AVP 100 m=video 30000 RTP/AVP 100
c=IN IP4 233.252.0.1/127 c=IN IP4 233.252.0.1/127
a=source-filter:incl IN IP4 233.252.0.1 198.51.100.1 a=source-filter:incl IN IP4 233.252.0.1 198.51.100.1
a=rtpmap:100 MP2T/90000 a=rtpmap:100 MP2T/90000
a=mid:S1a a=mid:S1a
m=video 30000 RTP/AVP 101 m=video 30000 RTP/AVP 101
c=IN IP4 233.252.0.2/127 c=IN IP4 233.252.0.2/127
a=source-filter:incl IN IP4 233.252.0.2 198.51.100.1 a=source-filter:incl IN IP4 233.252.0.2 198.51.100.1
a=rtpmap:101 MP2T/90000 a=rtpmap:101 MP2T/90000
a=mid:S1b a=mid:S1b
Optionally, one could be more explicit and insert an "a=duplication- Optionally, one could be more explicit and insert an
delay:0" line before the first "m" line. "a=duplication-delay:0" line before the first "m" line.
4.3. Temporal Redundancy 4.3. Temporal Redundancy
In this example, the redundant streams have the same IP source and In this example, the redundant streams have the same IP source and
destination addresses (i.e., they are transmitted in the same SSM destination addresses (i.e., they are transmitted in the same SSM
session). Due to the same source and destination addresses, the session). Due to the same source and destination addresses, the
packets in both streams will be routed over the same path. To packets in both streams will be routed over the same path. To
provide resiliency against packet loss, the duplicate of an original provide resiliency against packet loss, the duplicate of an original
packet is transmitted 50 ms later as indicated by the 'duplication- packet is transmitted 50 milliseconds (ms) later as indicated by the
delay' attribute (defined in [I-D.ietf-mmusic-delayed-duplication]). "duplication-delay" attribute (defined in [DELAYED-DUP]).
v=0 v=0
o=ali 1122334455 1122334466 IN IP4 dup.example.com o=ali 1122334455 1122334466 IN IP4 dup.example.com
s=Delayed Duplication s=Delayed Duplication
t=0 0 t=0 0
m=video 30000 RTP/AVP 100 m=video 30000 RTP/AVP 100
c=IN IP4 233.252.0.1/127 c=IN IP4 233.252.0.1/127
a=source-filter:incl IN IP4 233.252.0.1 198.51.100.1 a=source-filter:incl IN IP4 233.252.0.1 198.51.100.1
a=rtpmap:100 MP2T/90000 a=rtpmap:100 MP2T/90000
a=ssrc:1000 cname:ch1a@example.com a=ssrc:1000 cname:ch1a@example.com
a=ssrc:1010 cname:ch1a@example.com a=ssrc:1010 cname:ch1a@example.com
a=ssrc-group:DUP 1000 1010 a=ssrc-group:DUP 1000 1010
a=duplication-delay:50 a=duplication-delay:50
a=mid:Ch1 a=mid:Ch1
5. Security Considerations 5. Security Considerations
In general, the security considerations of [RFC4566] apply to this In general, the security considerations of [RFC4566] apply to this
document as well. document as well.
There is a weak threat for the receiver that the duplication grouping There is a weak threat for the receiver that the duplication grouping
can be modified to indicate relationships that do not exist. Such can be modified to indicate relationships that do not exist. Such
attacks might result in failure of the duplication mechanisms, and/or attacks might result in failure of the duplication mechanisms and/or
mishandling of the media streams by the receivers. mishandling of the media streams by the receivers.
In order to avoid attacks of this sort, the SDP description needs to In order to avoid attacks of this sort, the SDP description needs to
be integrity protected and provided with source authentication. This be integrity protected and provided with source authentication. This
can, for example, be achieved on an end-to-end basis using S/MIME can, for example, be achieved on an end-to-end basis using S/MIME
[RFC5652] [RFC5751] when the SDP is used in a signaling packet using [RFC5652] [RFC5751] when the SDP is used in a signaling packet using
MIME types (application/sdp). Alternatively, HTTPS [RFC2818] or the MIME types (application/sdp). Alternatively, HTTPS [RFC2818] or the
authentication method in the Session Announcement Protocol (SAP) authentication method in the Session Announcement Protocol (SAP)
[RFC2974] could be used as well. As for the confidentiality, if it [RFC2974] could be used as well. As for the confidentiality, if it
is desired, it can be useful to use a secure, encrypted transport is desired, it can be useful to use a secure, encrypted transport
method to carry the SDP description. method to carry the SDP description.
6. IANA Considerations 6. IANA Considerations
This document registers the following semantics with IANA in This document registers the following semantics with IANA in the
Semantics for the 'group' SDP Attribute under SDP Parameters: "Semantics for the "group" SDP Attribute" subregistry (under the
"Session Description Protocol (SDP) Parameters" registry:
Note to the RFC Editor: In the following registrations, please
replace "XXXX" with the number of this document prior to publication
as an RFC.
Semantics Token Reference Semantics Token Reference
------------------------------------- ------ --------- ------------------------------------- ------ ---------
Duplication DUP [RFCXXXX] Duplication DUP [RFC7104]
This document also registers the following semantics with IANA in This document also registers the following semantics with IANA in the
Semantics for the 'ssrc-group' SDP Attribute under SDP Parameters: "Semantics for the "ssrc-group" SDP Attribute" subregistry under the
"Session Description Protocol (SDP) Parameters" registry:
Token Semantics Reference Token Semantics Reference
------- ----------------------------- --------- ------- ----------------------------- ---------
DUP Duplication [RFCXXXX] DUP Duplication [RFC7104]
7. Acknowledgments 7. Acknowledgments
The authors would like to thank Colin Perkins, Bill Ver Steeg, Dave The authors would like to thank Colin Perkins, Bill Ver Steeg, Dave
Oran and Toerless Eckert for their inputs and suggestions. Oran, and Toerless Eckert for their input and suggestions.
8. References 8. References
8.1. Normative References 8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264, June with Session Description Protocol (SDP)", RFC 3264, June
skipping to change at page 7, line 52 skipping to change at page 9, line 7
[RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific
Media Attributes in the Session Description Protocol Media Attributes in the Session Description Protocol
(SDP)", RFC 5576, June 2009. (SDP)", RFC 5576, June 2009.
[RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
Protocol (SDP) Grouping Framework", RFC 5888, June 2010. Protocol (SDP) Grouping Framework", RFC 5888, June 2010.
8.2. Informative References 8.2. Informative References
[I-D.ietf-avtext-rtp-duplication] [DELAYED-DUP]
Begen, A. and C. Perkins, "Duplicating RTP Streams",
draft-ietf-avtext-rtp-duplication-04 (work in progress),
October 2013.
[I-D.ietf-mmusic-delayed-duplication]
Begen, A., Cai, Y., and H. Ou, "Delayed Duplication Begen, A., Cai, Y., and H. Ou, "Delayed Duplication
Attribute in the Session Description Protocol", draft- Attribute in the Session Description Protocol", Work in
ietf-mmusic-delayed-duplication-02 (work in progress), May Progress, December 2013.
2013.
[IC2011] Evans, J., Begen, A., Greengrass, J., and C. Filsfils, [IC2011] Evans, J., Begen, A., Greengrass, J., and C. Filsfils,
"Toward Lossless Video Transport, IEEE Internet Computing, "Toward Lossless Video Transport, IEEE Internet Computing,
vol. 15/6, pp. 48-57", November 2011. vol. 15/6, pp. 48-57", November 2011.
[RFC2354] Perkins, C. and O. Hodson, "Options for Repair of [RFC2354] Perkins, C. and O. Hodson, "Options for Repair of
Streaming Media", RFC 2354, June 1998. Streaming Media", RFC 2354, June 1998.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC2974] Handley, M., Perkins, C., and E. Whelan, "Session [RFC2974] Handley, M., Perkins, C., and E. Whelan, "Session
Announcement Protocol", RFC 2974, October 2000. Announcement Protocol", RFC 2974, October 2000.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, September 2009. RFC 5652, September 2009.
[RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet [RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
Mail Extensions (S/MIME) Version 3.2 Message Mail Extensions (S/MIME) Version 3.2 Message
Specification", RFC 5751, January 2010. Specification", RFC 5751, January 2010.
[RTP-DUP] Begen, A. and C. Perkins, "Duplicating RTP Streams", Work
in Progress, October 2013.
Authors' Addresses Authors' Addresses
Ali Begen Ali Begen
Cisco Cisco
181 Bay Street 181 Bay Street
Toronto, ON M5J 2T3 Toronto, ON M5J 2T3
Canada Canada
Email: abegen@cisco.com EMail: abegen@cisco.com
Yiqun Cai Yiqun Cai
Microsoft Microsoft
1065 La Avenida 1065 La Avenida
Mountain View, CA 94043 Mountain View, CA 94043
USA USA
Email: yiqunc@microsoft.com EMail: yiqunc@microsoft.com
Heidi Ou Heidi Ou
Cisco Cisco
170 W. Tasman Dr. 170 W. Tasman Dr.
San Jose, CA 95134 San Jose, CA 95134
USA USA
Email: hou@cisco.com EMail: hou@cisco.com
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