draft-ietf-avt-srtp-not-mandatory-04.txt		draft-ietf-avt-srtp-not-mandatory-05.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: June 25, 2010 Ericsson		Expires: July 26, 2010 Ericsson
	December 22, 2009		January 22, 2010
	Why RTP Does Not Mandate a Single Security Mechanism		Why RTP Does Not Mandate a Single Security Mechanism
	draft-ietf-avt-srtp-not-mandatory-04.txt		draft-ietf-avt-srtp-not-mandatory-05.txt
			Abstract
			This memo discusses the problem of securing real-time multimedia
			sessions, and explains why the Real-time Transport Protocol (RTP),
			and the associated RTP control protocol (RTCP), do not mandate a
			single media security mechanism.
	Status of this Memo		Status of this Memo
	This Internet-Draft is submitted to IETF 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 June 25, 2010.		This Internet-Draft will expire on July 26, 2010.
	Copyright Notice		Copyright Notice
	Copyright (c) 2009 IETF Trust and the persons identified as the		Copyright (c) 2010 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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			to this document. Code Components extracted from this document must
	Abstract		include Simplified BSD License text as described in Section 4.e of
			the Trust Legal Provisions and are provided without warranty as
	This memo discusses the problem of securing real-time multimedia		described in the Simplified BSD License.
	sessions, and explains why the Real-time Transport Protocol (RTP),
	and the associated RTP control protocol (RTCP), do not mandate a
	single media security mechanism.
	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 . . . 6
	6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 7		6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 7
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 7		7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	skipping to change at page 3, line 21		skipping to change at page 3, line 21
	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.
	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: we begin, in Section 2 by		The structure of this memo is as follows. Section 2 describes the
	describing the scenarios in which RTP is deployed. Following this,		scenarios in which RTP is deployed. Following this, Section 3
	Section 3 outlines the implications of this range of scenarios for		outlines the implications of this range of scenarios for media
	media confidentially and authentication, and Section 4 outlines the		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 meets the requirement of BCP 61. Section 6 then concludes
	and gives some recommendations. Finally, Section 7 outlines the		and gives some recommendations.
	security considerations, and Section 8 outlines IANA considerations.
	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 video conferencing
	skipping to change at page 5, line 22		skipping to change at page 5, line 22
	[ETSI.TS.102.474], where one mode of operation uses ISMAcryp		[ETSI.TS.102.474], where one mode of operation uses ISMAcryp
	(http://www.isma.tv/specs/ISMA_E&Aspec2.0.pdf) to encrypt the RTP		(http://www.isma.tv/specs/ISMA_E&Aspec2.0.pdf) to encrypt the RTP
	payload data only.		payload data only.
	Finally, the link layer may be secure, and it may be known that the		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		RTP media data is constrained to that single link (for example, when
	operating in a studio environment, with physical link security). An		operating in a studio environment, with physical link security). An
	environment like this is inherently constrained, but might avoid the		environment like this is inherently constrained, but might avoid the
	need for application, transport, or network layer media security.		need for application, transport, or network layer media security.
	All these are application scenarios where RTP has seen commerical		All these are application scenarios where RTP has seen commercial
	deployment. Other use case also exist, with additional requirements.		deployment. Other use case also exist, with additional requirements.
	There is no media security protocol that is appropriate for all these		There is no media security protocol that is appropriate for all these
	environments. Accordingly, multiple RTP media security protocols can		environments. Accordingly, multiple RTP media security protocols can
	be expected to remain in wide use.		be expected to remain in wide use.
	4. Implications for Key Management		4. Implications for Key Management
	With such a diverse range of use case 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 The most common use case for RTP is probably point-to-point voice		o The most common use case for RTP is probably point-to-point voice
	calls or centralised group conferences, negotiated using SIP		calls or centralised group conferences, negotiated using SIP
	[RFC3261] with the SDP offer/answer model [RFC3264], operating on		[RFC3261] with the SDP offer/answer model [RFC3264], operating on
	skipping to change at page 6, line 12		skipping to change at page 6, line 12
	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.		is run on the media path, bypassing the untrusted infrastructure.
	Protocols such as DTLS [I-D.ietf-avt-dtls-srtp] or ZRTP		Protocols such as DTLS [I-D.ietf-avt-dtls-srtp] or ZRTP
	[I-D.zimmermann-avt-zrtp] are useful here.		[I-D.zimmermann-avt-zrtp] are useful here.
	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.
	o A session description may be sent by email, secured using X.500 or		o A session description may be sent by email, secured using S/MIME
	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,
	skipping to change at page 8, line 31		skipping to change at page 8, line 31
	[I-D.ietf-avt-dtls-srtp]		[I-D.ietf-avt-dtls-srtp]
	McGrew, D. and E. Rescorla, "Datagram Transport Layer		McGrew, D. and E. Rescorla, "Datagram Transport Layer
	Security (DTLS) Extension to Establish Keys for Secure		Security (DTLS) Extension to Establish Keys for Secure
	Real-time Transport Protocol (SRTP)",		Real-time Transport Protocol (SRTP)",
	draft-ietf-avt-dtls-srtp-07 (work in progress),		draft-ietf-avt-dtls-srtp-07 (work in progress),
	February 2009.		February 2009.
	[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-21 (work in		(RTSP)", draft-ietf-mmusic-rfc2326bis-22 (work in
	progress), June 2009.		progress), July 2009.
	[I-D.ietf-sip-media-security-requirements]		[I-D.ietf-sip-media-security-requirements]
	Wing, D., Fries, S., Tschofenig, H., and F. Audet,		Wing, D., Fries, S., Tschofenig, H., and F. Audet,
	"Requirements and Analysis of Media Security Management		"Requirements and Analysis of Media Security Management
	Protocols", draft-ietf-sip-media-security-requirements-09		Protocols", draft-ietf-sip-media-security-requirements-09
	(work in progress), January 2009.		(work in progress), January 2009.
	[I-D.zimmermann-avt-zrtp]		[I-D.zimmermann-avt-zrtp]
	Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media		Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media
	Path Key Agreement for Secure RTP",		Path Key Agreement for Secure RTP",
	draft-zimmermann-avt-zrtp-15 (work in progress),		draft-zimmermann-avt-zrtp-17 (work in progress),
	March 2009.		January 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".
End of changes. 13 change blocks.
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