draft-ietf-straw-b2bua-dtls-srtp-06.txt   draft-ietf-straw-b2bua-dtls-srtp-07.txt 
STRAW R. Ravindranath STRAW R. Ravindranath
Internet-Draft T. Reddy Internet-Draft T. Reddy
Intended status: Standards Track G. Salgueiro Intended status: Standards Track G. Salgueiro
Expires: February 22, 2016 Cisco Expires: March 17, 2016 Cisco
V. Pascual V. Pascual
Quobis Quobis
Parthasarathi. Ravindran Parthasarathi. Ravindran
Nokia Networks Nokia Networks
August 21, 2015 September 14, 2015
DTLS-SRTP Handling in Session Initiation Protocol (SIP) Back-to-Back DTLS-SRTP Handling in Session Initiation Protocol (SIP) Back-to-Back
User Agents (B2BUAs) User Agents (B2BUAs)
draft-ietf-straw-b2bua-dtls-srtp-06 draft-ietf-straw-b2bua-dtls-srtp-07
Abstract Abstract
Session Initiation Protocol (SIP) Back-to-Back User Agents (B2BUAs) Session Initiation Protocol (SIP) Back-to-Back User Agents (B2BUAs)
often act on the media plane, rather than just on the signaling path. often act on the media plane, rather than just on the signaling path.
This document describes the behavior such B2BUAs should adhere to This document describes the behavior such B2BUAs can adhere to when
when acting on the media plane that uses an Secure Real-time acting on the media plane that uses an Secure Real-time Transport
Transport (SRTP) security context set up with the Datagram Transport (SRTP) security context set up with the Datagram Transport Layer
Layer Security (DTLS) protocol. Security (DTLS) protocol.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. 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
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 February 22, 2016. This Internet-Draft will expire on March 17, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 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 21 skipping to change at page 2, line 21
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Media Plane B2BUA Handling of DTLS-SRTP . . . . . . . . . . . 4 3. Media Plane B2BUA Handling of DTLS-SRTP . . . . . . . . . . . 4
3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1.1. Media Relay . . . . . . . . . . . . . . . . . . . . . 4 3.1.1. Media Relay . . . . . . . . . . . . . . . . . . . . . 4
3.1.2. Media Aware B2BUA . . . . . . . . . . . . . . . . . . 6 3.1.2. RTP/RTCP-aware Media Aware B2BUA . . . . . . . . . . 6
3.2. Media Plane B2BUA with NAT Handling . . . . . . . . . . . 7 3.2. Media Plane B2BUA with NAT Handling . . . . . . . . . . . 7
4. Forking Considerations . . . . . . . . . . . . . . . . . . . 7 4. Forking Considerations . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 10 9.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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[RFC5763] describes how Session Initiation Protocol (SIP) [RFC3261] [RFC5763] describes how Session Initiation Protocol (SIP) [RFC3261]
can be used to establish a Secure Real-time Transport Protocol (SRTP) can be used to establish a Secure Real-time Transport Protocol (SRTP)
[RFC3711] security context with the Datagram Transport Layer Security [RFC3711] security context with the Datagram Transport Layer Security
(DTLS) [RFC6347] protocol. It describes a mechanism for transporting (DTLS) [RFC6347] protocol. It describes a mechanism for transporting
a certificate fingerprint using Session Description Protocol (SDP) a certificate fingerprint using Session Description Protocol (SDP)
[RFC4566]. The fingerprint, identifies the certificate that will be [RFC4566]. The fingerprint, identifies the certificate that will be
presented during the DTLS handshake. DTLS-SRTP is defined for point- presented during the DTLS handshake. DTLS-SRTP is defined for point-
to-point media sessions, in which there are exactly two participants. to-point media sessions, in which there are exactly two participants.
Each DTLS-SRTP session (described in Section 3 of [RFC5764]) contains Each DTLS-SRTP session (described in Section 3 of [RFC5764]) contains
a single DTLS connection, and either two SRTP contexts (if media a single DTLS connection (if RTP and RTCP are multiplexed) or two
traffic is flowing in both directions on the same 5-tuple) or one DTLS connections (if RTP and RTCP are not multiplexed), and either
SRTP context (if media traffic is only flowing in one direction). two SRTP contexts (if media traffic is flowing in both directions on
the same 5-tuple) or one SRTP context (if media traffic is only
flowing in one direction).
In many SIP deployments, SIP Back-to-Back User Agents (B2BUA) In many SIP deployments, SIP Back-to-Back User Agents (B2BUA)
entities exist on the SIP signaling path between the endpoints. As entities exist on the SIP signaling path between the endpoints. As
described in [RFC7092], these B2BUAs may modify SIP and SDP described in [RFC7092], these B2BUAs can modify SIP and SDP
information. They may also be present on the media path, in which information. They can also be present on the media path, in which
case they may modify parts of the SDP information (like IP address, case they modify parts of the SDP information (like IP address, port)
port) and subsequently modify the RTP headers as well. Such B2BUAs and subsequently modify the RTP headers as well. Such B2BUAs are
are referred to as media plane B2BUAs referred to as media plane B2BUAs.
1.2. Goals 1.2. Goals
[RFC7092] describes two different categories of media plane B2BUAs, [RFC7092] describes two different categories of media plane B2BUAs,
according to the level of activities performed on the media plane: according to the level of activities performed on the media plane:
A B2BUA that acts as a simple media relay effectively unaware of A B2BUA that acts as a simple media relay effectively unaware of
anything that is transported and only terminates the media plane anything that is transported and only terminates the media plane
at the IP and transport (UDP/TCP) layers. at the IP and transport (UDP/TCP) layers.
A B2BUA that performs a media-aware role. It inspects and A B2BUA that performs a media-aware role. It inspects and
potentially modifies RTP or RTP Control Protocol (RTCP) headers; potentially modifies RTP headers or RTP Control Protocol (RTCP)
but it does not modify the payload of RTP/RTCP. packets.
The following sections describe the behavior B2BUAs should follow in The following sections describe the behavior B2BUAs MUST follow in
order to avoid any impact to end-to-end DTLS-SRTP streams. order to avoid any impact to end-to-end DTLS-SRTP sessions.
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 this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
The following generalized terms are defined in [RFC3261], Section 6. The following generalized terms are defined in [RFC3261], Section 6.
B2BUA: a SIP Back-to-Back User Agent, which is the logical B2BUA: a SIP Back-to-Back User Agent, which is the logical
skipping to change at page 5, line 51 skipping to change at page 5, line 51
Figure 1: INVITE with SDP call-flow for Media Relay B2BUA Figure 1: INVITE with SDP call-flow for Media Relay B2BUA
NOTE: For brevity the entire value of the SDP fingerprint attribute NOTE: For brevity the entire value of the SDP fingerprint attribute
is not shown. The example here shows only one DTLS connection for is not shown. The example here shows only one DTLS connection for
the sake of simplicity. In reality depending on whether the RTP and the sake of simplicity. In reality depending on whether the RTP and
RTCP flows are multiplexed or demultiplexed there will be one or two RTCP flows are multiplexed or demultiplexed there will be one or two
DTLS connections. DTLS connections.
If RTP and RTCP traffic is multiplexed as described in [RFC5761] on a If RTP and RTCP traffic is multiplexed as described in [RFC5761] on a
single port then only a single DTLS connection would be required single port then only a single DTLS connection is required between
between the peers. If RTP and RTCP are not multiplexed, then the the peers. If RTP and RTCP are not multiplexed, then the peers would
peers would have to establish two DTLS connections. In this case, have to establish two DTLS connections. In this case, Bob, after he
Bob, after he receives an INVITE request, triggers the establishment receives an INVITE request, triggers the establishment of a DTLS
of a DTLS connection. Note that the DTLS handshake and the sending connection. Note that the DTLS handshake and the sending of INVITE
of INVITE response may happen in parallel; thus, the B2BUA SHOULD be response can happen in parallel; thus, the B2BUA SHOULD be prepared
prepared to receive DTLS, STUN and media on the ports it advertised to receive DTLS, STUN and media on the ports it advertised to Bob in
to Bob in the INVITE request. Since a media relay B2BUA does not the INVITE request. Since a media relay B2BUA does not differentiate
differentiate between a DTLS message, RTP or any packet it receives, between a DTLS message, RTP or any packet it receives, it only
it only changes the transport layer (UDP/TCP) and IP headers and changes the transport layer (UDP/TCP) and IP headers and forwards the
forwards the packet towards the other endpoint. packet towards the other endpoint. B2BUA cannot decrypt the RTP
payload as the payload is encrypted using the SRTP keys derived from
the DTLS connection setup between Alice and Bob.
[I-D.ietf-stir-rfc4474bis] provides a means for signing portions of [I-D.ietf-stir-rfc4474bis] provides a means for signing portions of
SIP requests in order to provide identity assurance and certificate SIP requests in order to provide identity assurance and certificate
pinning by providing a signature over the fingerprint of keying pinning by providing a signature over the fingerprint of keying
material in SDP for DTLS-SRTP [RFC5763]. A media relay B2BUA MUST material in SDP for DTLS-SRTP [RFC5763]. A media relay B2BUA MUST
ensure that it does not modify any of the information used to ensure that it does not modify any of the information used to
construct the signature. construct the signature.
In the above example, Alice may be authorized by the authorization In the above example, Alice can be authorized by the authorization
server (SIP proxy) in its domain using the procedures in Section 5 of server (SIP proxy) in its domain using the procedures in Section 5 of
[I-D.ietf-stir-rfc4474bis]. In such a case, if the B2BUA modifies [I-D.ietf-stir-rfc4474bis]. In such a case, if the B2BUA modifies
some of the SIP headers or SDP content that was used by Alice's some of the SIP headers or SDP content that was used by Alice's
authorization server to generate the identity, it would break the authorization server to generate the identity, it would break the
identity verification procedure explained in Section 4.2 of identity verification procedure explained in Section 4.2 of
[I-D.ietf-stir-rfc4474bis] resulting in a 438 error response being [I-D.ietf-stir-rfc4474bis] resulting in a 438 error response being
returned. returned.
3.1.2. Media Aware B2BUA 3.1.2. RTP/RTCP-aware Media Aware B2BUA
Unlike the media relay discussed in Section 3.1.1, a media-aware Unlike the media relay discussed in Section 3.1.1, a media-aware
relay as defined in Section 3.2.2 of [RFC7092], is aware of the type relay as defined in Section 3.2.2 of [RFC7092], is aware of the type
of media traffic it is receiving. A media-aware relay inspects of media traffic it is receiving. There are two types of media-aware
received SRTP and SRTCP packets and may modify the headers before relay, those that merely inspect the RTP headers and RTCP packets,
forwarding the packets. and those that inspect and modify the RTP headers and RTCP packets.
The mechanism described in Security Considerations section MUST be
used by endpoint to detect malicious B2BUA's that MAY attempt to
terminate the DTLS-SRTP session.
3.1.2.1. RTP and RTCP Header Inspection 3.1.2.1. RTP header and RTCP packets Inspection
A media-aware relay does not modify the RTP and RTCP headers but only This kind of media aware relay does not modify the RTP headers and
inspects the header values. It MUST NOT terminate the DTLS-SRTP RTCP packets but only inspects the packets. It MUST NOT terminate
connection on which the packets are received. the DTLS-SRTP session on which the packets are received.
3.1.2.2. RTP and RTCP Header Modification 3.1.2.2. RTP header and RTCP packet Modification
In addition to inspecting the RTP and RTCP headers, a media-aware In order to modify headers a B2BUA needs to act as a DTLS endpoint
relay may also modify them. In order to modify headers a B2BUA needs and terminate the DTLS-SRTP session and decrypt/re-encrypt RTP
to act as a DTLS endpoint and terminate the DTLS connection and payload. This would break end-to-end security and hence a B2BUA MUST
decrypt/re-encrypt RTP packets. This would break end-to-end security NOT terminate DTLS-SRTP session. This security and privacy problem
and hence a B2BUA MUST NOT terminate DTLS-SRTP sessions. This can be mitigated by having different keys for protecting RTP header
security and privacy problem can be mitigated by having separate keys integrity and encrypting the RTP payload. For example, the approach
for encrypting the RTP header and media payload as discussed in discussed in [I-D.jones-perc-private-media-reqts] can be used. With
[I-D.jones-perc-private-media-reqts]. With such an approach, the such an approach, the B2BUA is not aware of the keys used to decrypt
B2BUA is not aware of the keys used to decrypt the media payload. the media payload.
3.2. Media Plane B2BUA with NAT Handling 3.2. Media Plane B2BUA with NAT Handling
DTLS-SRTP handshakes and SDP offer/answer exchanges [RFC3264] may DTLS-SRTP handshakes and SDP offer/answer exchanges [RFC3264] may
happen in parallel. If an endpoint is behind a NAT, and the endpoint happen in parallel. If an endpoint is behind a NAT, and the endpoint
is acting as a DTLS server, the ClientHello message from a B2BUA is acting as a DTLS server, the ClientHello message from a B2BUA
(acting as DTLS client) is likely to be lost, as described in (acting as DTLS client) is likely to be lost, as described in
Section 7.3 of [RFC5763]. In order to overcome this problem, the Section 7.3 of [RFC5763]. In order to overcome this problem, the
endpoint and B2BUA can support the Interactive Connectivity endpoint and B2BUA can support the Interactive Connectivity
Establishment (ICE) mechanism [RFC5245], as discussed in Section 7.3 Establishment (ICE) mechanism [RFC5245], as discussed in Section 7.3
of [RFC5763]. If the ICE check is successful then the endpoint will of [RFC5763]. If the ICE check is successful then the endpoint will
receive the ClientHello message from the B2BUA. receive the ClientHello message from the B2BUA.
4. Forking Considerations 4. Forking Considerations
Due to forking [RFC3261], a SIP request carrying an SDP offer sent by Due to forking [RFC3261], a SIP request carrying an SDP offer sent by
an endpoint (offerer) may reach multiple remote endpoints. As a an endpoint (offerer) can reach multiple remote endpoints. As a
result, multiple DTLS-SRTP connections may be established, one result, multiple DTLS-SRTP sessions can be established, one between
between the endpoint that sent the SIP request and each of the remote the endpoint that sent the SIP request and each of the remote
endpoints that received the request. Both media relays and media- endpoints that received the request. Both media relays and media-
aware relays MUST forward the certificate fingerprints and SDP setup aware relays MUST forward the certificate fingerprints and SDP setup
attributes it received in the SDP answer from each endpoint attributes it received in the SDP answer from each endpoint
(answerer) unmodified towards the offerer. Since DTLS operates on (answerer) unmodified towards the offerer. Since DTLS operates on
the 5-tuple, B2BUA MUST replace the answerer's transport addresses in the 5-tuple, B2BUA MUST replace the answerer's transport addresses in
each answer with its unique transport addresses so that the offerer each answer with its unique transport addresses so that the offerer
can establish a DTLS connection with each answerer. can establish a DTLS connection with each answerer.
Bob (192.0.2.1:6666) Bob (192.0.2.1:6666)
/ /
skipping to change at page 8, line 29 skipping to change at page 8, line 29
\ \
\ \
Charlie (192.0.2.2:6666) Charlie (192.0.2.2:6666)
Figure 2: B2BUA handling multiple answers Figure 2: B2BUA handling multiple answers
For instance, as shown in Figure 2 Alice sends a request with an For instance, as shown in Figure 2 Alice sends a request with an
offer, and the request is forked. Alice receives answers from both offer, and the request is forked. Alice receives answers from both
Bob and Charlie. B2BUA MUST advertise different B2BUA transport Bob and Charlie. B2BUA MUST advertise different B2BUA transport
address in each answer, as shown in Figure2, where XXX and YYY address in each answer, as shown in Figure2, where XXX and YYY
represent different DTLS-SRTP connections. B2BUA replaces the Bob's represent different DTLS-SRTP sessions. B2BUA replaces the Bob's
transport address (192.0.2.1:6666) in the answer with its transport transport address (192.0.2.1:6666) in the answer with its transport
address (192.0.2.3:7777) and Charlie's transport address address (192.0.2.3:7777) and Charlie's transport address
(192.0.2.2:6666) in the answer with its transport address (192.0.2.2:6666) in the answer with its transport address
(192.0.2.3:8888). B2BUA tracks the remote sources (Bob and Charlie) (192.0.2.3:8888). B2BUA tracks the remote sources (Bob and Charlie)
and associates them to the local sources that are used to send and associates them to the local sources that are used to send
packets to Alice. packets to Alice.
5. Security Considerations 5. Security Considerations
This document describes the behavior media plane B2BUAs (media-aware This document describes the behavior media plane B2BUAs (media-aware
and media-unaware) should follow when acting on the media plane that and media-unaware) MUST follow when acting on the media plane that
uses SRTP security context setup with the DTLS protocol. Attempting uses SRTP security context setup with the DTLS protocol. Attempting
to cover media-aware relay and media termination scenarios involving to cover media-aware relay modifying RTP headers and media
secure sessions (like DTLS-SRTP) will inevitably lead to the B2BUA termination scenarios involving secure sessions (like DTLS-SRTP) will
acting as a man-in-the-middle, and as such its behavior is inevitably lead to the B2BUA acting as a man-in-the-middle, and hence
unspecified and discouraged. This document does not introduce any a B2BUA MUST NOT terminate DTLS-SRTP session. This document does not
specific security considerations beyond those detailed in [RFC5763]. introduce any specific security considerations beyond those detailed
In addition, the B2BUA behaviors outlined in this document do not in [RFC5763]. In addition, the B2BUA behaviors outlined in this
impact the security and integrity of a DTLS-SRTP connection or the document do not impact the security and integrity of a DTLS-SRTP
data exchanged over it. A malicious B2BUA may try to break into the session or the data exchanged over it. A malicious B2BUA MAY try to
DTLS connection, but such an attack can be prevented using the break into the DTLS connection, but such an attack can be prevented
identity validation mechanism discussed in using the identity validation mechanism discussed in [RFC4474] and
[I-D.ietf-stir-rfc4474bis]. getting updated in [I-D.ietf-stir-rfc4474bis]. Either the endpoints
or authentication service proxies involved in the call MUST use the
identity validation mechanisms discussed in [RFC4474] to validate the
identity of peers and detect malicious B2BUA's that can attempt to
terminate the DTLS connection to decrypt the RTP payload.
6. IANA Considerations 6. IANA Considerations
This document makes no request of IANA. This document makes no request of IANA.
7. Acknowledgments 7. Acknowledgments
Special thanks to Lorenzo Miniero, Ranjit Avarsala, Hadriel Kaplan, Special thanks to Lorenzo Miniero, Ranjit Avarsala, Hadriel Kaplan,
Muthu Arul Mozhi, Paul Kyzivat, Peter Dawes, Brett Tate, Dan Wing, Muthu Arul Mozhi, Paul Kyzivat, Peter Dawes, Brett Tate, Dan Wing,
Charles Eckel, Simon Perreault, Albrecht Schwarz, Jens Guballa and Charles Eckel, Simon Perreault, Albrecht Schwarz, Jens Guballa,
Christer Holmberg for their constructive comments,suggestions, and Christer Holmberg and Colin Perkins for their constructive
early reviews that were critical to the formulation and refinement of comments,suggestions, and early reviews that were critical to the
this document. formulation and refinement of this document.
8. Contributors 8. Contributors
Rajeev Seth provided substantial contributions to this document. Rajeev Seth provided substantial contributions to this document.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
skipping to change at page 9, line 41 skipping to change at page 9, line 45
[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, DOI 10.17487/RFC3550, Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>. July 2003, <http://www.rfc-editor.org/info/rfc3550>.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)", Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, DOI 10.17487/RFC3711, March 2004, RFC 3711, DOI 10.17487/RFC3711, March 2004,
<http://www.rfc-editor.org/info/rfc3711>. <http://www.rfc-editor.org/info/rfc3711>.
[RFC4474] Peterson, J. and C. Jennings, "Enhancements for
Authenticated Identity Management in the Session
Initiation Protocol (SIP)", RFC 4474,
DOI 10.17487/RFC4474, August 2006,
<http://www.rfc-editor.org/info/rfc4474>.
[RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
for Establishing a Secure Real-time Transport Protocol for Establishing a Secure Real-time Transport Protocol
(SRTP) Security Context Using Datagram Transport Layer (SRTP) Security Context Using Datagram Transport Layer
Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May
2010, <http://www.rfc-editor.org/info/rfc5763>. 2010, <http://www.rfc-editor.org/info/rfc5763>.
[RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer [RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer
Security (DTLS) Extension to Establish Keys for the Secure Security (DTLS) Extension to Establish Keys for the Secure
Real-time Transport Protocol (SRTP)", RFC 5764, Real-time Transport Protocol (SRTP)", RFC 5764,
DOI 10.17487/RFC5764, May 2010, DOI 10.17487/RFC5764, May 2010,
skipping to change at page 10, line 21 skipping to change at page 10, line 33
[I-D.ietf-avtext-rtp-grouping-taxonomy] [I-D.ietf-avtext-rtp-grouping-taxonomy]
Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and
B. Burman, "A Taxonomy of Semantics and Mechanisms for B. Burman, "A Taxonomy of Semantics and Mechanisms for
Real-Time Transport Protocol (RTP) Sources", draft-ietf- Real-Time Transport Protocol (RTP) Sources", draft-ietf-
avtext-rtp-grouping-taxonomy-08 (work in progress), July avtext-rtp-grouping-taxonomy-08 (work in progress), July
2015. 2015.
[I-D.ietf-stir-rfc4474bis] [I-D.ietf-stir-rfc4474bis]
Peterson, J., Jennings, C., and E. Rescorla, Peterson, J., Jennings, C., and E. Rescorla,
"Authenticated Identity Management in the Session "Authenticated Identity Management in the Session
Initiation Protocol (SIP)", draft-ietf-stir-rfc4474bis-04 Initiation Protocol (SIP)", draft-ietf-stir-rfc4474bis-05
(work in progress), July 2015. (work in progress), September 2015.
[I-D.jones-perc-private-media-reqts] [I-D.jones-perc-private-media-reqts]
Jones, P., Ismail, N., Benham, D., Buckles, N., Mattsson, Jones, P., Ismail, N., Benham, D., Buckles, N., Mattsson,
J., and R. Barnes, "Private Media Requirements in Privacy J., and R. Barnes, "Private Media Requirements in Privacy
Enhanced RTP Conferencing", draft-jones-perc-private- Enhanced RTP Conferencing", draft-jones-perc-private-
media-reqts-00 (work in progress), July 2015. media-reqts-00 (work in progress), July 2015.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
 End of changes. 25 change blocks. 
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