draft-ietf-avt-srtp-not-mandatory-07.txt   draft-ietf-avt-srtp-not-mandatory-08.txt 
Network Working Group C. Perkins Network Working Group C. Perkins
Internet-Draft University of Glasgow Internet-Draft University of Glasgow
Intended status: Informational M. Westerlund Intended status: Informational M. Westerlund
Expires: January 2, 2011 Ericsson Expires: May 3, 2012 Ericsson
July 1, 2010 October 31, 2011
Why RTP Does Not Mandate a Single Security Mechanism Why RTP Does Not Mandate a Single Security Mechanism
draft-ietf-avt-srtp-not-mandatory-07.txt draft-ietf-avt-srtp-not-mandatory-08.txt
Abstract Abstract
This memo discusses the problem of securing real-time multimedia This memo discusses the problem of securing real-time multimedia
sessions, and explains why the Real-time Transport Protocol (RTP), sessions, and explains why the Real-time Transport Protocol (RTP),
and the associated RTP control protocol (RTCP), do not mandate a and the associated RTP control protocol (RTCP), do not mandate a
single media security mechanism. single media security mechanism. It also discusses how applications
using RTP can meet the goals of BCP 61 to have strong and mandatory
to implement security.
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.
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This Internet-Draft will expire on January 2, 2011. This Internet-Draft will expire on May 3, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. RTP Applications and Deployment Scenarios . . . . . . . . . . 3 2. RTP Applications and Deployment Scenarios . . . . . . . . . . 3
3. Implications for RTP Security . . . . . . . . . . . . . . . . 4 3. Implications for RTP Security . . . . . . . . . . . . . . . . 4
4. Implications for Key Management . . . . . . . . . . . . . . . 5 4. Implications for Key Management . . . . . . . . . . . . . . . 5
5. On the Requirement for Strong Security in IETF protocols . . . 6 5. On the Requirement for Strong Security in IETF protocols . . . 7
6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
10. Informative References . . . . . . . . . . . . . . . . . . . . 8 10. Informative References . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction 1. Introduction
The Real-time Transport Protocol (RTP) [RFC3550] is widely used for The Real-time Transport Protocol (RTP) [RFC3550] is widely used for
voice over IP, Internet television, video conferencing, and various voice over IP, Internet television, video conferencing, and various
other real-time and streaming media applications. Despite this, the other real-time and streaming media applications. Despite this, the
base RTP specification provides very limited options for media base RTP specification provides very limited options for media
security, and defines no standard key exchange mechanism. Rather, a security, and defines no standard key exchange mechanism. Rather, a
number of extensions are defined to provide confidentiality and number of extensions are defined to provide confidentiality and
authentication of RTP media streams and RTCP control messages, and to authentication of RTP media streams and RTCP control messages, and to
exchange security keys. This memo outlines why it is appropriate exchange security keys. This memo outlines why it is appropriate
that multiple extension mechanisms are defined, rather than mandating that multiple extension mechanisms are defined, rather than mandating
a single security and keying mechanism. a single security and keying mechanism.
The consensus for Strong Security Requirements for IETF Standard
Protocols (BCP61) [RFC3365] describes the Danvers Doctrine, which
states that:
"The solution is that we MUST implement strong security in all
protocols to provide for the all too frequent day when the
protocol comes into widespread use in the global Internet."
BCP 61 also discusses that security must be implemented, and makes
the following statement:
"However security must be a MUST IMPLEMENT so that end users will
have the option of enabling it when the situation calls for it."
This IETF consensus provides a clear challange for RTP security, due
to the heterogenous scenarios in which RTP can be used, and the wide
choice of security mechanisms available. This memo describes how RTP
based applications, or classes of applications, can best meet the
security goals of BCP 61.
This memo provides information for the community; it does not specify This memo provides information for the community; it does not specify
a standard of any kind. a standard of any kind.
The structure of this memo is as follows. Section 2 describes the The structure of this memo is as follows. Section 2 describes a
scenarios in which RTP is deployed. Following this, Section 3 number of scenarios in which RTP is deployed. Following this,
outlines the implications of this range of scenarios for media Section 3 outlines the implications of this range of scenarios for
confidentially and authentication, and Section 4 outlines the media confidentially and authentication, and Section 4 outlines the
implications for key exchange. Section 5 outlines how the RTP implications for key exchange. Section 5 outlines how the RTP
framework meets the requirement of BCP 61. Section 6 then concludes framework can meet the requirement of BCP 61. Section 6 then
and gives some recommendations. concludes and gives some recommendations.
2. RTP Applications and Deployment Scenarios 2. RTP Applications and Deployment Scenarios
The range of application and deployment scenarios where RTP has been The range of application and deployment scenarios where RTP has been
used includes, but is not limited to, the following: used includes, but is not limited to, the following:
o Point-to-point voice telephony (fixed and wireless networks) o Point-to-point voice telephony (fixed and wireless networks)
o Point-to-point video conferencing o Point-to-point voice and video conferencing
o Centralised group video conferencing with a multipoint conference o Centralised group video conferencing with a multipoint conference
unit (MCU) unit (MCU)
o Any Source Multicast video conferencing (light-weight sessions; o Any Source Multicast video conferencing (light-weight sessions;
Mbone conferencing) Mbone conferencing)
o Point-to-point streaming audio and/or video o Point-to-point streaming audio and/or video
o Source-specific multicast (SSM) streaming to large group (IPTV and o Source-specific multicast (SSM) streaming to large group (IPTV and
skipping to change at page 4, line 41 skipping to change at page 5, line 13
headers) to provide some degree of confidentiality, and providing headers) to provide some degree of confidentiality, and providing
optional source origin authentication. It was carefully designed to optional source origin authentication. It was carefully designed to
be both low overhead, and to support the group communication features be both low overhead, and to support the group communication features
of RTP, across a range of networks. of RTP, across a range of networks.
SRTP is not the only media security solution in use, however, and SRTP is not the only media security solution in use, however, and
alternatives are more appropriate for some scenarios. For example, alternatives are more appropriate for some scenarios. For example,
many client-server streaming media applications can run over a single many client-server streaming media applications can run over a single
TCP connection, multiplexing media data with control information on TCP connection, multiplexing media data with control information on
that connection (RTSP [I-D.ietf-mmusic-rfc2326bis] is a widely used that connection (RTSP [I-D.ietf-mmusic-rfc2326bis] is a widely used
example of such a protocol). The natural way to provide media example of such a protocol). One way to provide media security for
security for such client-server media applications is to use TLS such client-server media applications is to use TLS [RFC5246] to
[RFC5246] to protect the TCP connection, sending the RTP media data protect the TCP connection, sending the RTP media data over the TLS
over the TLS connection. Using the SRTP framework in addition to TLS connection. Using the SRTP framework in addition to TLS is
is unnecessary, and would result in double encryption of the media, unnecessary, and would result in double encryption of the media, and
and SRTP cannot be used instead of TLS since it is RTP-specific, and SRTP cannot be used instead of TLS since it is RTP-specific, and so
so cannot protect the control traffic. cannot protect the control traffic.
Other RTP use cases work over networks which provide security at the Other RTP use cases work over networks which provide security at the
network layer, using IPsec. For example, certain 3GPP networks need network layer, using IPsec. For example, certain 3GPP networks need
IPsec security associations for other purposes, and can reuse those IPsec security associations for other purposes, and can reuse those
to secure the RTP session [3GPP.33.210]. SRTP is, again, unnecessary to secure the RTP session [TS-33210]. SRTP is, again, unnecessary in
in such environments, and its use would only introduce overhead for such environments, and its use would only introduce overhead for no
no gain. gain.
For some applications it is sufficient to protect the RTP payload For some applications it is sufficient to protect the RTP payload
data while leaving RTP, transport, and network layer headers data while leaving RTP, transport, and network layer headers
unprotected. An example of this is RTP broadcast over DVB-H unprotected. An example of this is RTP broadcast over DVB-H
[ETSI.TS.102.474], where one mode of operation uses ISMAcryp [ETSI.TS.102.474], where one mode of operation uses ISMA Cryp 2.0
(http://www.isma.tv/specs/ISMA_E&Aspec2.0.pdf) to encrypt the RTP [ISMA] to encrypt the RTP payload data only.
payload data only.
Finally, the link layer may be secure, and it may be known that the
RTP media data is constrained to that single link (for example, when
operating in a studio environment, with physical link security). An
environment like this is inherently constrained, but might avoid the
need for application, transport, or network layer media security.
All these are application scenarios where RTP has seen commercial All these are application scenarios where RTP has seen commercial
deployment. Other use case also exist, with additional requirements. deployment. Other use cases exist, with additional requirements.
There is no media security protocol that is appropriate for all these For example, if the media transport is done over UDP [RFC0768], DCCP
environments. Accordingly, multiple RTP media security protocols can [RFC4340] or SCTP [RFC4960], then using DTLS [RFC4347] to protect the
be expected to remain in wide use. whole RTP packets is an option. There is no media security protocol
that is appropriate for all these environments. Accordingly,
multiple RTP media security protocols can be expected to remain in
wide use.
4. Implications for Key Management 4. Implications for Key Management
With such a diverse range of use cases come a range of different With such a diverse range of use cases come a range of different
protocols for RTP session establishment. Mechanisms used to provide protocols for RTP session establishment. Mechanisms used to provide
security keying for these different session establishment protocols security keying for these different session establishment protocols
can basically be put into two categories: inband and out-of-band in can basically be put into two categories: inband and out-of-band in
relation to the session establishment mechanism. The requirements relation to the session establishment mechanism. The requirements
for these solutions are highly varying. Thus a wide range of for these solutions are highly varying. Thus a wide range of
solutions have been developed in this space: solutions have been developed in this space:
o A common use case for RTP is probably point-to-point voice calls o A common use case for RTP is probably point-to-point voice calls
or centralised group conferences, negotiated using SIP [RFC3261] or centralised group conferences, negotiated using SIP [RFC3261]
with the SDP offer/answer model [RFC3264], operating on a trusted with the SDP offer/answer model [RFC3264], operating on a trusted
infrastructure. In such environments, SDP security descriptions infrastructure. In such environments, SDP security descriptions
[RFC4568] or the MIKEY [RFC4567] protocol are appropriate keying [RFC4568], or the MIKEY [RFC3830] protocol using the Key
mechanisms, piggybacked onto the SDP [RFC4566] exchange. The Management Extensions for SDP [RFC4567], are appropriate keying
infrastructure may be secured by protecting the SIP exchange using mechanisms, where the keying messages/material are embedded in the
TLS or S/MIME, for example [RFC3261]. Protocols such as DTLS SDP [RFC4566] exchange. The infrastructure may be secured by
[RFC5764] or ZRTP [I-D.zimmermann-avt-zrtp] are also appropriate protecting the SDP exchange in SIP using TLS or S/MIME, for
in such environments. example [RFC3261]. Protocols such as DTLS-SRTP [RFC5764] or ZRTP
[RFC6189] are also appropriate in such environments.
o Point-to-point RTP sessions may be negotiated using SIP with the o Point-to-point RTP sessions may be negotiated using SIP with the
offer/answer model, but operating over a network with untrusted offer/answer model, but operating over a network with untrusted
infrastructure. In such environments, the key management protocol infrastructure. In such environments, the key management protocol
is run on the media path, bypassing the untrusted infrastructure. can be run on the media path, bypassing the untrusted
Protocols such as DTLS [RFC5764] or ZRTP [I-D.zimmermann-avt-zrtp] infrastructure. Protocols such as DTLS-SRTP [RFC5764] or ZRTP
are useful here. [RFC6189] are useful here, as are inband mechanism that protect
the keying material such as MIKEY [RFC3830] using the Key
Management Extensions for SDP [RFC4567]. It should be noted that
the end-points for all the above mechanisms must prevent total
downgrade to no security for the RTP media streams.
o For point-to-point client-server streaming of RTP over RTSP, a TLS o For point-to-point client-server streaming of RTP over RTSP, a TLS
association is appropriate to manage keying material, in much the association is appropriate to manage keying material, in much the
same manner as would be used to secure an HTTP session. same manner as would be used to secure an HTTP session. But also
using SRTP with DTLS-SRTP keying or DTLS are appropriate choices.
o A session description may be sent by email, secured using S/MIME o A session description may be sent by email, secured using S/MIME
or PGP, or retrieved from a web page, using HTTP with TLS. or PGP, or retrieved from a web page, using HTTP with TLS.
o A session description may be distributed to a multicast group o A session description may be distributed to a multicast group
using SAP or FLUTE secured with S/MIME. using SAP or FLUTE secured with S/MIME.
o A session description may be distributed using the Open Mobile o A session description may be distributed using the Open Mobile
Alliance DRM key management specification [OMA-DRM] when using a Alliance DRM key management specification [OMA-DRM] when using a
point-to-point streaming session setup with RTSP in the 3GPP PSS point-to-point streaming session setup with RTSP in the 3GPP PSS
environment [PSS]. environment [PSS].
o In the 3GPP Multimedia Broadcast Multicast Service (MBMS) system, o In the 3GPP Multimedia Broadcast Multicast Service (MBMS) system,
HTTP and MIKEY are used for key management [MBMS-SEC]. HTTP and MIKEY are used for key management [MBMS-SEC].
A more detailed survey of requirements for media security management A more detailed survey of requirements for media security management
protocols can be found in [RFC5479]. As can be seen, the range of protocols can be found in [RFC5479]. As can be seen, the range of
use cases is wide, and there is no single protocol that is use cases is wide, and there is no single protocol that is
appropriate for all scenarios. These solutions have been further appropriate for all scenarios. These solutions have been further
diversified by the existence of infrastructure elements such as diversified by the existence of infrastructure elements such as
authentication solutions that are tied into the key manangement. authentication solutions that are tied into the key management.
5. On the Requirement for Strong Security in IETF protocols 5. On the Requirement for Strong Security in IETF protocols
BCP 61 [RFC3365] puts a requirement on IETF protocols to provide BCP 61 [RFC3365] puts a requirement on IETF protocols to provide
strong, mandatory to implement, security solutions. This is actually strong, mandatory to implement, security solution. This is actually
quite a difficult requirement for any type of framework protocol, quite a difficult requirement for any type of framework protocol like
like RTP, since one can never know all the deployment scenarios, and RTP, or for that matter the Reliable Multicast Transport suite
[RFC3048], since one can never know all the deployment scenarios, and
if they are covered by the security solution. It would clearly be if they are covered by the security solution. It would clearly be
desirable if a single media security solution and a single key desirable if a single media security solution and a single key
management solution could be developed, satisfying the range of use management solution could be developed, satisfying the range of use
cases for RTP. The authors are not aware of any such solution, cases for RTP. The authors are not aware of any such solution,
however, and it is not clear that any single solution can be however, and believe it is unlikely that any single solution can be
developed. developed.
For a framework protocol it appears that the only sensible solution For a framework protocol it appears that the only sensible solution
to the requirement of BCP 61 is to develop or use security building to the requirement of BCP 61 is to develop or use security building
blocks, like SRTP, SDP security descriptions [RFC4568], MIKEY, DTLS, blocks, like SRTP, SDP security descriptions, MIKEY, DTLS, DTLS-SRTP,
or IPsec, to provide the basic security services of authorization, or IPsec, to provide the basic security services of authorization,
data integrity protection and date confidentiality protection. When data integrity protection and date confidentiality protection. When
new usages of the RTP framework arise, one needs to analyze the new usages of the RTP framework arise, one needs to analyze the
situation, to determine if the existing building blocks satisfy the situation, to determine if the existing building blocks satisfy the
requirements. If not, it is necessary to develop new security requirements. If not, it is necessary to develop new security
building blocks. building blocks.
When it comes to fulfilling the "MUST Implement" strong security for When it comes to fulfilling the "MUST Implement" strong security for
a specific application, it will fall on that application to actually a specific application, or class of applications, it will fall on
consider what building blocks it is required to support. To maximize that application to actually consider what building blocks it is
interoperability it is desirable if certain applications, or classes required to support. To maximize interoperability it is desirable if
of application with similar requirements, agree on what data security certain applications, or classes of application with similar
mechanisms and key-management should be used. If such agreement is requirements, agree on what data security mechanisms and key-
not possible, there will be increased cost, either in the lack of management should be used. If such agreement is not possible, there
interoperability, or in the need to implement more solutions. will be increased cost, either in the lack of interoperability, or in
Unfortunately this situation, if not handled reasonably well, can the need to implement more solutions. Unfortunately this situation,
result in a failure to satisfy the requirement of providing the users if not handled reasonably well, can result in a failure to satisfy
with an option of turning on strong security when desired. the requirement of providing the users with an option of turning on
strong security when desired.
The IETF needs to perform this selection of security building blocks
whenever it is possible. This can be done if the application, or
class of applications, is being specified within the IETF, or wich a
scope where the IETF can take the role to provide a security profile.
However, it is clear that many applications, or classes of
application, are specified outside the scope and influence of the
IETF. In those case we can't do other than strongly recommend these
organizations perform a security analysis, taking into account other
applications, to try to maximize the security and interoperability.
6. Conclusions 6. Conclusions
As discussed earlier it appears that a single solution can't be As discussed earlier it appears that a single solution can't be
designed to meet the diverse requirements. In the absence of such a designed to meet the diverse requirements. In the absence of such a
solution, it is hoped that this memo explains why SRTP is not solution, it is hoped that this memo explains why SRTP is not
mandatory as the media security solution for RTP-based systems, and mandatory as the media security solution for RTP-based systems, and
why we can expect multiple key management solutions for systems using why we can expect multiple key management solutions for systems using
RTP. RTP.
It is important for any RTP-based application to consider how it It is very important for any RTP-based application to consider how it
meets the security requirements. This will require some analysis to meets the security requirements. This will require some analysis to
determine these requirements, followed by the selection of a determine these requirements, followed by the selection of a
mandatory to implement solution, or in exceptional scenarios several mandatory to implement solution, or in exceptional scenarios several
solutions, including the desired RTP traffic protection and key- solutions, including the desired RTP traffic protection and key-
management. SRTP is a preferred solution for the protection of the management. When defining applications or protocols using RTP within
RTP traffic in those use cases where it is applicable. It is out of the IETF, the responsibility for fulfilling the BCP 61 requirements
scope for this memo to recommend a preferred key management solution. will fall onto the developers of these applications. IETF also
should be open to help other standards bodies by defining security
profiles suitable for classes of applications.
Anyone defining an RTP based application needs to take care to
consider how to fulfill its security goals and specify which
mechanisms that are to be implemented. In that work interoperability
with similar applications should be considered, so that when such
applications becomes desirable to interconnect those applications,
their security solutions are compatible and will not require
additional implementation or costly gateways that also reduce
security by forcing a trusted third party.
SRTP is a preferred solution for the protection of the RTP traffic in
those use cases where it is applicable. It is out of scope for this
memo to recommend a preferred key management solution in general.
The authors do note that DTLS-SRTP was developed in the IETF to meet
the goals of point to point media sessions established by SIP.
7. Security Considerations 7. Security Considerations
This entire memo is about security. This entire memo is about security.
8. IANA Considerations 8. IANA Considerations
No IANA actions are required. No IANA actions are required.
9. Acknowledgements 9. Acknowledgements
Thanks to Ralph Blom, Hannes Tschofenig, Dan York, Alfred Hoenes, Thanks to Ralph Blom, Hannes Tschofenig, Dan York, Alfred Hoenes,
Martin Ellis, Ali Begen, and Keith Drage for their feedback. Martin Ellis, Ali Begen, and Keith Drage for their feedback.
10. Informative References 10. Informative References
[3GPP.33.210]
3GPP, "IP network layer security", 3GPP TS 33.210.
[ETSI.TS.102.474] [ETSI.TS.102.474]
ETSI, "Digital Video Broadcasting (DVB); IP Datacast over ETSI, "Digital Video Broadcasting (DVB); IP Datacast over
DVB-H: Service Purchase and Protection", ETSI TS 102 474, DVB-H: Service Purchase and Protection", ETSI TS 102 474,
November 2007. November 2007.
[I-D.ietf-mmusic-rfc2326bis] [I-D.ietf-mmusic-rfc2326bis]
Schulzrinne, H., Rao, A., Lanphier, R., Westerlund, M., Schulzrinne, H., Rao, A., Lanphier, R., Westerlund, M.,
and M. Stiemerling, "Real Time Streaming Protocol 2.0 and M. Stiemerling, "Real Time Streaming Protocol 2.0
(RTSP)", draft-ietf-mmusic-rfc2326bis-23 (work in (RTSP)", draft-ietf-mmusic-rfc2326bis-28 (work in
progress), March 2010. progress), October 2011.
[I-D.zimmermann-avt-zrtp] [ISMA] Internet Streaming Media Alliance, "Encryption and
Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media Authentication Version 2.0", November 2007.
Path Key Agreement for Unicast Secure RTP",
draft-zimmermann-avt-zrtp-22 (work in progress),
June 2010.
[MBMS] 3GPP, "Multimedia Broadcast/Multicast Service (MBMS); [MBMS] 3GPP, "Multimedia Broadcast/Multicast Service (MBMS);
Protocols and codecs TS 26.346". Protocols and codecs TS 26.346".
[MBMS-SEC] [MBMS-SEC]
3GPP, "Security of Multimedia Broadcast/Multicast Service 3GPP, "Security of Multimedia Broadcast/Multicast Service
(MBMS) TS 33.246". (MBMS) TS 33.246".
[OMA-DRM] Open Mobile Alliance, "DRM Specification 2.0". [OMA-DRM] Open Mobile Alliance, "DRM Specification 2.0".
[PSS] 3GPP, "Transparent end-to-end Packet-switched Streaming [PSS] 3GPP, "Transparent end-to-end Packet-switched Streaming
Service (PSS); Protocols and codecs TS 26.234". Service (PSS); Protocols and codecs TS 26.234".
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980. August 1980.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981. RFC 793, September 1981.
[RFC3048] Whetten, B., Vicisano, L., Kermode, R., Handley, M.,
Floyd, S., and M. Luby, "Reliable Multicast Transport
Building Blocks for One-to-Many Bulk-Data Transfer",
RFC 3048, January 2001.
[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,
June 2002. June 2002.
[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, with Session Description Protocol (SDP)", RFC 3264,
June 2002. June 2002.
[RFC3365] Schiller, J., "Strong Security Requirements for Internet [RFC3365] Schiller, J., "Strong Security Requirements for Internet
Engineering Task Force Standard Protocols", BCP 61, Engineering Task Force Standard Protocols", BCP 61,
RFC 3365, August 2002. RFC 3365, August 2002.
skipping to change at page 9, line 24 skipping to change at page 10, line 22
RFC 3365, August 2002. RFC 3365, August 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.
[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, March 2004. RFC 3711, March 2004.
[RFC3830] Arkko, J., Carrara, E., Lindholm, F., Naslund, M., and K.
Norrman, "MIKEY: Multimedia Internet KEYing", RFC 3830,
August 2004.
[RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram [RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram
Congestion Control Protocol (DCCP)", RFC 4340, March 2006. Congestion Control Protocol (DCCP)", RFC 4340, March 2006.
[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, April 2006.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E. [RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E.
Carrara, "Key Management Extensions for Session Carrara, "Key Management Extensions for Session
Description Protocol (SDP) and Real Time Streaming Description Protocol (SDP) and Real Time Streaming
Protocol (RTSP)", RFC 4567, July 2006. Protocol (RTSP)", RFC 4567, July 2006.
[RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session
Description Protocol (SDP) Security Descriptions for Media Description Protocol (SDP) Security Descriptions for Media
Streams", RFC 4568, July 2006. Streams", RFC 4568, July 2006.
[RFC4614] Duke, M., Braden, R., Eddy, W., and E. Blanton, "A Roadmap [RFC4614] Duke, M., Braden, R., Eddy, W., and E. Blanton, "A Roadmap
for Transmission Control Protocol (TCP) Specification for Transmission Control Protocol (TCP) Specification
Documents", RFC 4614, September 2006. Documents", RFC 4614, September 2006.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008. (TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5479] Wing, D., Fries, S., Tschofenig, H., and F. Audet, [RFC5479] Wing, D., Fries, S., Tschofenig, H., and F. Audet,
"Requirements and Analysis of Media Security Management "Requirements and Analysis of Media Security Management
Protocols", RFC 5479, April 2009. Protocols", RFC 5479, April 2009.
[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, May 2010. Real-time Transport Protocol (SRTP)", RFC 5764, May 2010.
[RFC6189] Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media
Path Key Agreement for Unicast Secure RTP", RFC 6189,
April 2011.
[TS-33210]
3GPP, "IP network layer security", 3GPP TS 33.210.
Authors' Addresses Authors' Addresses
Colin Perkins Colin Perkins
University of Glasgow University of Glasgow
Department of Computing Science Department of Computing Science
Glasgow G12 8QQ Glasgow G12 8QQ
UK UK
Email: csp@csperkins.org Email: csp@csperkins.org
 End of changes. 33 change blocks. 
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