< draft-ietf-sipping-session-policy-req-01.txt		draft-ietf-sipping-session-policy-req-02.txt >
	SIPPING J. Rosenberg		SIPPING J. Rosenberg
	Internet-Draft dynamicsoft		Internet-Draft dynamicsoft
	Expires: August 16, 2004 February 16, 2004		Expires: January 17, 2005 July 19, 2004
	Requirements for Session Policy for the Session Initiation Protocol		Requirements for Session Policy for the Session Initiation Protocol
	(SIP)		(SIP)
	draft-ietf-sipping-session-policy-req-01		draft-ietf-sipping-session-policy-req-02
	Status of this Memo		Status of this Memo
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	all provisions of Section 10 of RFC2026.		patent or other IPR claims of which I am aware have been disclosed,
			and any of which I become aware will be disclosed, in accordance with
			RFC 3668.
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	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2004). All Rights Reserved.		Copyright (C) The Internet Society (2004). All Rights Reserved.
	Abstract		Abstract
	The proxy server plays a central role as an intermediary in the		The proxy server plays a central role as an intermediary in the
	establishment of sessions in the Session Initiation Protocol (SIP).		establishment of sessions in the Session Initiation Protocol (SIP).
	In that role, they can define and impact policies on call routing,		In that role, they can define and impact policies on call routing,
	rendezvous, and other call features. However, there is no standard		rendezvous, and other call features. However, there is no standard
	means by which proxies can have any influence on session policies,		means by which proxies can have any influence on session policies,
	such as the codecs that are to be used. As such, ad-hoc and		such as the codecs that are to be used. As such, ad-hoc and
	non-conformant techniques have been deployed to allow for such policy		non-conformant techniques have been deployed to allow for such policy
	mechanisms. There is a need for a standards-based and complete		mechanisms. There is a need for a standards-based and complete
	mechanism for session policies. This document defines a set of		mechanism for session policies. This document defines a set of
	requirements for such a mechanism.		requirements for such a mechanism.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Problems with Existing Situation . . . . . . . . . . . . . . . 5		2. Problems with Existing Situation . . . . . . . . . . . . . . . 5
	3. Requirements for a Solution . . . . . . . . . . . . . . . . . 7		3. Requirements for a Solution . . . . . . . . . . . . . . . . . 7
	3.1 General Requirements . . . . . . . . . . . . . . . . . . . . . 7		3.1 General Requirements . . . . . . . . . . . . . . . . . . . 7
	3.2 Policy Requirements . . . . . . . . . . . . . . . . . . . . . 7		3.2 Policy Requirements . . . . . . . . . . . . . . . . . . . 7
	3.3 Policy Types . . . . . . . . . . . . . . . . . . . . . . . . . 8		3.3 Policy Types . . . . . . . . . . . . . . . . . . . . . . . 8
	3.4 Consent Requirements . . . . . . . . . . . . . . . . . . . . . 9		3.4 Consent Requirements . . . . . . . . . . . . . . . . . . . 8
	3.5 Security Requirements . . . . . . . . . . . . . . . . . . . . 9		3.5 Security Requirements . . . . . . . . . . . . . . . . . . 9
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 11		4. Security Considerations . . . . . . . . . . . . . . . . . . . 10
	5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12		5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
	Informative References . . . . . . . . . . . . . . . . . . . . 13		6. Informative References . . . . . . . . . . . . . . . . . . . . 11
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . 14		Author's Address . . . . . . . . . . . . . . . . . . . . . . . 12
	Intellectual Property and Copyright Statements . . . . . . . . 15		Intellectual Property and Copyright Statements . . . . . . . . 13
	1. Introduction		1. Introduction
	The Session Initiation Protocol [2] enables the setup and management		The Session Initiation Protocol [2] enables the setup and management
	of interactive multimedia sessions on IP networks. A central element		of interactive multimedia sessions on IP networks. A central element
	in SIP is the proxy server. Proxies are responsible for request		in SIP is the proxy server. Proxies are responsible for request
	routing, rendezvous, authentication and authorization, mobility, and		routing, rendezvous, authentication and authorization, mobility, and
	other signaling services. However, proxies are divorced from the		other signaling services. However, proxies are divorced from the
	actual sessions - audio, video, and messaging - that SIP establishes.		actual sessions - audio, video, and messaging - that SIP establishes.
	Details of the sessions are carried in the payload of SIP messages,		Details of the sessions are carried in the payload of SIP messages,
	and are usually described with the Session Description Protocol (SDP)		and are usually described with the Session Description Protocol (SDP)
	[1]. Indeed, SIP provides end-to-end encryption features using S/		[1]. Indeed, SIP provides end-to-end encryption features using S/
	MIME, so that all information about the sessions can be hidden from		MIME, so that all information about the sessions can be hidden from
	eavesdroppers and proxies alike.		eavesdroppers and proxies alike.
	However, experience has shown that there is a need for SIP		However, experience has shown that there is a need for SIP
	intermediaries to impact aspects of the session. One aspect is the		intermediaries to impact aspects of the session. One aspect is the
	path that the media streams will take. Frequently, a SIP provider		path that the media streams will take. Frequently, a SIP provider
	will need or want the media to traverse some kind of intermediary,		will need or want the media to traverse some kind of intermediary,
	such as a NAT. Indeed, the central concept of the midcom framework		such as a NAT. Indeed, the central concept of the midcom framework
	[4] is to define a model of how this can be done. In this model, a		[4] is to define a model of how this can be done. In this model, a
	midcom agent, typically a proxy server, interacts with the middlebox		midcom agent, typically a proxy server, interacts with the middlebox
	to open and close media pinholes, obtain NAT bindings, and so on. In		to open and close media pinholes, obtain NAT bindings, and so on. In
	this role as a midcom agent, the proxy will need to examine and		this role as a midcom agent, the proxy will need to examine and
	possibly modify the session description in the body of the SIP		possibly modify the session description in the body of the SIP
	message. This modification is to achieve a specific policy objective:		message. This modification is to achieve a specific policy
	to force the media to route through an intermediary.		objective: to force the media to route through an intermediary.
	In another application, SIP is used in a wireless network. The		In another application, SIP is used in a wireless network. The
	network provider has limited resources for media traffic. During		network provider has limited resources for media traffic. During
	periods of high activity, the provider would like to restrict codec		periods of high activity, the provider would like to restrict codec
	usage on the network to lower rate codecs.		usage on the network to lower rate codecs.
	In yet a third application, SIP is used in a network that has		In yet a third application, SIP is used in a network that has
	gateways which support a single codec type (say, G.729). When		gateways which support a single codec type (say, G.729). When
	communicating with a partner network that uses gateways with a		communicating with a partner network that uses gateways with a
	different codec (say, G.723), the network modifies the SDP to route		different codec (say, G.723), the network modifies the SDP to route
	the session through a converter that changes the G.729 to G.723.		the session through a converter that changes the G.729 to G.723.
	The desire to impact aspects of the session inevitably occurs in		The desire to impact aspects of the session inevitably occurs in
	domains where the administrator of the SIP domain is also the owner		domains where the administrator of the SIP domain is also the owner
	and administrator of an IP network over which it is known that the		and administrator of an IP network over which it is known that the
	sessions will traverse. This includes enterprises, Internet access		sessions will traverse. This includes enterprises, Internet access
	providers, and in some cases, backbone providers.		providers, and in some cases, backbone providers.
	Since SIP is the protocol by which the details of these sessions are		Since SIP is the protocol by which the details of these sessions are
	negotiated, it is natural for providers to wish to impose their		negotiated, it is natural for providers to wish to impose their
	session policies through some kind of SIP means. To date, this has		session policies through some kind of SIP means. To date, this has
	been accomplished through SDP editing, a process where proxies dig		been accomplished through SDP editing, a process where proxies dig
	into the bodies of SIP messages, and modify them in order to impose		into the bodies of SIP messages, and modify them in order to impose
	their policies. However, this SIP editing technique has many		their policies. However, this SIP editing technique has many
	drawbacks.		drawbacks.
	2. Problems with Existing Situation		2. Problems with Existing Situation
	RFC 3261 explicitly disallows proxy servers from manipulating the		RFC 3261 explicitly disallows proxy servers from manipulating the
	content of bodies. This is at odds with the common industry practice		content of bodies. This is at odds with the common industry practice
	of extensive manipulation of bodies by proxies. Although a common		of extensive manipulation of bodies by proxies. Although a common
	practice, it is at odds with the SIP specification for many reasons:		practice, it is at odds with the SIP specification for many reasons:
	End-to-End Encryption: SIP uses S/MIME to support end-to-end		End-to-End Encryption: SIP uses S/MIME to support end-to-end
	security security features. Authentication, message integrity, and		security security features. Authentication, message integrity,
	encryption are provided. The encryption capabilities are important		and encryption are provided. The encryption capabilities are
	for end-to-end privacy services, for example. The end-to-end		important for end-to-end privacy services, for example. The
	message integrity and authentication are important for preventing		end-to-end message integrity and authentication are important for
	numerous attacks, including theft of calls, eavesdropping attacks,		preventing numerous attacks, including theft of calls,
	and so on. If end-to-end authentication is used, any manipulation		eavesdropping attacks, and so on. If end-to-end authentication is
	of the body will cause the message integrity check to fail. If		used, any manipulation of the body will cause the message
	end-to-end encryption is used, the proxy won't even be able to		integrity check to fail. If end-to-end encryption is used, the
	look at the SDP to modify it. In this case, media may not		proxy won't even be able to look at the SDP to modify it. In this
	function, and the call will fail.		case, media may not function, and the call will fail.
	Require Processing: A UA may require that an extension be applied		Require Processing: A UA may require that an extension be applied
	to the SDP body. This is accomplished by including a Require		to the SDP body. This is accomplished by including a Require
	header in the SIP message. Proxies do not look at such headers. If		header in the SIP message. Proxies do not look at such headers.
	the proxy processes the SDP without understanding the extension,		If the proxy processes the SDP without understanding the
	it may improperly modify the SDP, resulting in a call failure.		extension, it may improperly modify the SDP, resulting in a call
			failure.
	Consent: Ultimately, end users need to be in control of the media		Consent: Ultimately, end users need to be in control of the media
	they send. If a user makes a call through a SIP network, they have		they send. If a user makes a call through a SIP network, they
	the expectation that their media is delivered to the recipient. By		have the expectation that their media is delivered to the
	having proxies modify the SDP in some way, they act in ways		recipient. By having proxies modify the SDP in some way, they act
	outside of expected behavior of the system.		in ways outside of expected behavior of the system.
	Future Proofing: One of the benefits of the SIP architecture is		Future Proofing: One of the benefits of the SIP architecture is
	that only the endpoints need to understand sessions, session		that only the endpoints need to understand sessions, session
	descriptions, bodies, and so on. This facilitates the use of proxy		descriptions, bodies, and so on. This facilitates the use of
	networks to provide communications services for future session		proxy networks to provide communications services for future
	types, such as games and messaging. However, if proxies require an		session types, such as games and messaging. However, if proxies
	understanding of session types and session descriptions, the SIP		require an understanding of session types and session
	network becomes locked in to providing features for a particular		descriptions, the SIP network becomes locked in to providing
	set of session types. If a new session description protocol, such		features for a particular set of session types. If a new session
	as SDPng [10], were introduced, calls would not function even		description protocol, such as SDPng [10], were introduced, calls
	though the endpoints support SDPng. Furthermore, it would be hard		would not function even though the endpoints support SDPng.
	to determine why it did not function, since the failure would		Furthermore, it would be hard to determine why it did not
	occur transparently in some proxy in the middle of the network.		function, since the failure would occur transparently in some
			proxy in the middle of the network.
	Robustness: Having a proxy manipulate the body introduces a host		Robustness: Having a proxy manipulate the body introduces a host
	of new failure modes into the network. Firstly, the proxy itself		of new failure modes into the network. Firstly, the proxy itself
	will need to have state in some form in order to properly		will need to have state in some form in order to properly
	manipulate the SDP. This means that, should the proxy fail, the		manipulate the SDP. This means that, should the proxy fail, the
	call may not be able to continue. Secondly, proxies typically		call may not be able to continue. Secondly, proxies typically
	won't enforce the media policy. Rather, they leave that to some		won't enforce the media policy. Rather, they leave that to some
	media middlebox somewhere on the media path. This media middlebox		media middlebox somewhere on the media path. This media middlebox
	may fail as well. Since the user does not know of its existence,		may fail as well. Since the user does not know of its existence,
	they may not be able to detect this failure or retry the media		they may not be able to detect this failure or retry the media
	path around it.		path around it.
	Scalability: One of the reasons SIP scales so well is that proxies		Scalability: One of the reasons SIP scales so well is that proxies
	don't have to be aware of the details of the sessions being		don't have to be aware of the details of the sessions being
	established through them. If a proxy needs to examine and/or		established through them. If a proxy needs to examine and/or
	manipulate session descriptions, this could require many		manipulate session descriptions, this could require many
	additional processing steps. The proxy may need to traverse a		additional processing steps. The proxy may need to traverse a
	multi-part body to find the SDP, in the case of SIP-T [5]. The		multi-part body to find the SDP, in the case of SIP-T [5]. The
	proxy will need to parse, modify, and possibly re-serialize the		proxy will need to parse, modify, and possibly re-serialize the
	session description. All of this requires additional processing		session description. All of this requires additional processing
	that worsens the performance of the proxies.		that worsens the performance of the proxies.
	We note that many of these problems are similar to those pointed out		We note that many of these problems are similar to those pointed out
	by the IAB regarding Open Pluggable Exchange Services (OPES) [6].		by the IAB regarding Open Pluggable Exchange Services (OPES) [6].
	Indeed, the problems are similar. Both have to do with the		Indeed, the problems are similar. Both have to do with the
	involvement of intermediaries in manipulation of end-to-end content.		involvement of intermediaries in manipulation of end-to-end content.
	Here, the content is not in the body itself, but is a session		Here, the content is not in the body itself, but is a session
	described by the body.		described by the body.
	We believe a better solution is needed.		We believe a better solution is needed.
	3. Requirements for a Solution		3. Requirements for a Solution
	In order to prevent the continuing usage of SDP editing to achieve		In order to prevent the continuing usage of SDP editing to achieve
	session policies, we believe explicit protocol support is needed to		session policies, we believe explicit protocol support is needed to
	provide a mechanism that can overcome the limitations above. As per		provide a mechanism that can overcome the limitations above. As per
	the IETF SIP change process [7], the first step in any such activity		the IETF SIP change process [7], the first step in any such activity
	is to specify requirements for the solution. This section is an		is to specify requirements for the solution. This section is an
	enumeration of those requirements.		enumeration of those requirements.
	3.1 General Requirements		3.1 General Requirements
	REQ-GEN-1: The solution should work even with SIP end-to-end		REQ-GEN-1: The solution should work even with SIP end-to-end
	encryption and end-to-end authentication enabled.		encryption and end-to-end authentication enabled.
	REQ-GEN-2: The solution should not force a proxy to violate the SIP		REQ-GEN-2: The solution should not force a proxy to violate the SIP
	specification or any defined extensions.		specification or any defined extensions.
	REQ-GEN-3: The solution should not require substantial processing		REQ-GEN-3: The solution should not require substantial processing
	burden on the proxies.		burden on the proxies.
	REQ-GEN-4: The solution should not require proxies to understand a		REQ-GEN-4: The solution should not require proxies to understand a
	specific type of session description (i.e., SDP or SDPng).		specific type of session description (i.e., SDP or SDPng).
	REQ-GEN-5: The solution should have a minimal impact on call setup		REQ-GEN-5: The solution should have a minimal impact on call setup
	delays, and ideally, have no impact on call setup delays.		delays, and ideally, have no impact on call setup delays.
	REQ-GEN-6: The solution should require minimal overhead, since it is		REQ-GEN-6: The solution should require minimal overhead, since it is
	anticipated to receive wide use in wireless networks.		anticipated to receive wide use in wireless networks.
	REQ-GEN-7: The solution should be extensible, supporting new session		REQ-GEN-7: The solution should be extensible, supporting new session
	policy types in the future.		policy types in the future.
	REQ-GEN-8: The solution must not require that the proxies be in the		REQ-GEN-8: The solution must not require that the proxies be in the
	same administrative domain as the media intermediaries.		same administrative domain as the media intermediaries.
	3.2 Policy Requirements		3.2 Policy Requirements
	REQ-POL-1: The solution should allow specification of independent		REQ-POL-1: The solution should allow specification of independent
	policies by each proxy along the call setup path, without any		policies by each proxy along the call setup path, without any
	coordination between proxies.		coordination between proxies.
	REQ-POL-2: The solution should allow a proxy to specify media		REQ-POL-2: The solution should allow a proxy to specify media
	policies on a stream-by-stream basis.		policies on a stream-by-stream basis.
	REQ-POL-3: When used in conjunction with the offer/answer model [3],		REQ-POL-3: When used in conjunction with the offer/answer model [3],
	the solution should allow a proxy to specify independent policies		the solution should allow a proxy to specify independent policies
	for the media streams in each direction.		for the media streams in each direction.
	REQ-POL-4: The mechanism must provide the ability to inform the UA		REQ-POL-4: The mechanism must provide the ability to inform the UA
	about the set of session-independent session policies when the		about the set of session-independent session policies when the
	device starts up. These are session policies that do not depend on		device starts up. These are session policies that do not depend
	a particular session.		on a particular session.
	REQ-POL-5: The mechanism must allow the provider to change the		REQ-POL-5: The mechanism must allow the provider to change the
	session-independent policies at least a few times a day.		session-independent policies at least a few times a day.
	REQ-POL-6: The mechanism must allow the session independent policies		REQ-POL-6: The mechanism must allow the session independent policies
	to vary on a user by user basis.		to vary on a user by user basis.
	REQ-POL-7 The mechanism must provide a way to inform the client about		REQ-POL-7 The mechanism must provide a way to inform the client about
	changes in session independent session policies when they occur.		changes in session independent session policies when they occur.
	3.3 Policy Types		3.3 Policy Types
	REQ-POL-4: The solution should allow a proxy to request media		REQ-POL-4: The solution should allow a proxy to request media
	sessions to traverse through one or more intermediaries.		sessions to traverse through one or more intermediaries.
	REQ-POL-5: The solution should allow a proxy to request a specific		REQ-POL-5: The solution should allow a proxy to request a specific
	source routing mechanism to be used (when applicable) in order to		source routing mechanism to be used (when applicable) in order to
	traverse those intermediaries. The source routing technique may be		traverse those intermediaries. The source routing technique may
	media-specific, or a generic technique, such as IP-in-IP [8]		be media-specific, or a generic technique, such as IP-in-IP [8]
	REQ-POL-6: Intermediaries must be identifiable using either an IP		REQ-POL-6: Intermediaries must be identifiable using either an IP
	address or an FQDN, in order to support DNS-based load balancing		address or an FQDN, in order to support DNS-based load balancing
	and failover techniques.		and failover techniques.
	REQ-POL-7: The solution should allow a proxy to inspect the addresses		REQ-POL-7: The solution should allow a proxy to inspect the addresses
	for the media sessions, so that it can set policies in intervening		for the media sessions, so that it can set policies in intervening
	firewalls.		firewalls.
	REQ-POL-8: The solution should allow proxies to request that a		REQ-POL-8: The solution should allow proxies to request that a
	particular media stream not be used (video, for example).		particular media stream not be used (video, for example).
	REQ-POL-9: The solution should allow proxies to request that a		REQ-POL-9: The solution should allow proxies to request that a
	particular codec not be used.		particular codec not be used.
	REQ-POL-10: The solution should allow proxies to express preferences		REQ-POL-10: The solution should allow proxies to express preferences
	for the use of particular codecs.		for the use of particular codecs.
	REQ-POL-11: The solution should allow proxies to request that Quality		REQ-POL-11: The solution should allow proxies to request that Quality
	of Service (QoS) should be requested for a stream.		of Service (QoS) should be requested for a stream.
	REQ-POL-12: The solution should allow proxies to ask endpoints to use		REQ-POL-12: The solution should allow proxies to ask endpoints to use
	specific parameters in their QoS reservations.		specific parameters in their QoS reservations.
	REQ-POL-13: The solution should allow proxies to ask endpoints to		REQ-POL-13: The solution should allow proxies to ask endpoints to
	provide a specific credential in their QoS requests. This		provide a specific credential in their QoS requests. This
	requirement covers the functionality currently described in [9].		requirement covers the functionality currently described in [9].
	3.4 Consent Requirements		3.4 Consent Requirements
	Consent plays a critical role for this problem. End users must be		Consent plays a critical role for this problem. End users must be
	allowed control over how they communicate with each other. Indeed,		allowed control over how they communicate with each other. Indeed,
	with end-to-end IP connectivity, there is frequently little the		with end-to-end IP connectivity, there is frequently little the
	provider can do to force users to communicate one way or another.		provider can do to force users to communicate one way or another.
	Ultimately, any means a provider comes up with can be circumvented by		Ultimately, any means a provider comes up with can be circumvented by
	some creative engineering in the clients. As such, policy requests by		some creative engineering in the clients. As such, policy requests
	proxies are just that - requests, and are ultimately honored at the		by proxies are just that - requests, and are ultimately honored at
	discretion of the end users. The mechanism needs to recognize this,		the discretion of the end users. The mechanism needs to recognize
	and be engineered to work within this model, rather than try to work		this, and be engineered to work within this model, rather than try to
	around it.		work around it.
	REQ-CON-1: The mechanism should allow the UAC to know the set of		REQ-CON-1: The mechanism should allow the UAC to know the set of
	policies requested by the proxies along the call path. [[OPEN		policies requested by the proxies along the call path. [[OPEN
	ISSUE: Is it more important for the UAC to know about changes		ISSUE: Is it more important for the UAC to know about changes
	requested for media in one direction or the other?]]		requested for media in one direction or the other?]]
	REQ-CON-2: The mechanism should allow the UAS to know the set of		REQ-CON-2: The mechanism should allow the UAS to know the set of
	policies requested by the proxies along the call path.		policies requested by the proxies along the call path.
	REQ-CON-3: The mechanism should allow the UAC to reject any policy		REQ-CON-3: The mechanism should allow the UAC to reject any policy
	requests made by proxies.		requests made by proxies.
	REQ-CON-4: The mechanism should allow the UAS to reject any policy		REQ-CON-4: The mechanism should allow the UAS to reject any policy
	requests made by proxies.		requests made by proxies.
	REQ-CON-5: The mechanism should allow the proxies to know whether or		REQ-CON-5: The mechanism should allow the proxies to know whether or
	not the UAC has accepted its policy requests.		not the UAC has accepted its policy requests.
	REQ-CON-6: The mechanism should allow the proxies to know whether or		REQ-CON-6: The mechanism should allow the proxies to know whether or
	not the UAS has accepted its policy requests.		not the UAS has accepted its policy requests.
	REQ-CON-7: The mechanism should allow the proxies to inform the UAC		REQ-CON-7: The mechanism should allow the proxies to inform the UAC
	and UAS of the consequences of non-compliance to the policies.		and UAS of the consequences of non-compliance to the policies.
	Potential consequences include call rejection, degraded media		Potential consequences include call rejection, degraded media
	quality, lack of connectivity for a media stream, and so on.		quality, lack of connectivity for a media stream, and so on.
	3.5 Security Requirements		3.5 Security Requirements
	REQ-SEC-1: The mechanism should allow user agents to verify the		REQ-SEC-1: The mechanism should allow user agents to verify the
	identity of the providers requesting the session policies.		identity of the providers requesting the session policies.
	REQ-SEC-2: The mechanism should allow user agents to verify the		REQ-SEC-2: The mechanism should allow user agents to verify the
	integrity of the session policies.		integrity of the session policies.
	REQ-SEC-3: The mechanism must provide assurances to the UAC and UAS		REQ-SEC-3: The mechanism must provide assurances to the UAC and UAS
	that only proxies on the actual SIP signaling path have requested		that only proxies on the actual SIP signaling path have requested
	session policies.		session policies.
	REQ-SEC-4: The mechanism should allow proxies to ensure the		REQ-SEC-4: The mechanism should allow proxies to ensure the
	confidentiality of the session policies, so that no one but the		confidentiality of the session policies, so that no one but the
	UAC or UAS can observe them. [[OPEN ISSUE: Is this really a		UAC or UAS can observe them. [[OPEN ISSUE: Is this really a
	requirement?]]		requirement?]]
	REQ-SEC-5: The mechanism must not enable any new denial-of-service		REQ-SEC-5: The mechanism must not enable any new denial-of-service
	attacks to be launched. [[OPEN ISSUE: This is motherhood and apple		attacks to be launched. [[OPEN ISSUE: This is motherhood and
	pie - does it need to be here?]]		apple pie - does it need to be here?]]
	REQ-SEC-6: The mechanism shall still allow for media security through		REQ-SEC-6: The mechanism shall still allow for media security through
	Secure RTP [11]. In the case of intermediaries which process the		Secure RTP [11]. In the case of intermediaries which process the
	RTP in some way that would invalidate any signatures, the UAs must		RTP in some way that would invalidate any signatures, the UAs must
	be aware of the presence of the intermediary, and perform key		be aware of the presence of the intermediary, and perform key
	exchanges with it. [[OPEN ISSUE: This may be an impossible		exchanges with it. [[OPEN ISSUE: This may be an impossible
	requirement to meet without using a B2BUA.]]		requirement to meet without using a B2BUA.]]
	4. Security Considerations		4. Security Considerations
	Requirements related to security are considered in Section 3.5.		Requirements related to security are considered in Section 3.5.
	5. Acknowledgements		5. Acknowledgements
	I would like to thank Volker Hilt, Gonzalo Camarillo, Miguel Garcia		I would like to thank Volker Hilt, Gonzalo Camarillo, Miguel Garcia
	and Kumiko Ono for their input.		and Kumiko Ono for their input.
	Informative References		6 Informative References
	[1] Handley, M. and V. Jacobson, "SDP: Session Description		[1] Handley, M. and V. Jacobson, "SDP: Session Description
	Protocol", RFC 2327, April 1998.		Protocol", RFC 2327, April 1998.
	[2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,		[2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
	Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:		Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
	Session Initiation Protocol", RFC 3261, June 2002.		Session Initiation Protocol", RFC 3261, June 2002.
	[3] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with		[3] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
	Session Description Protocol (SDP)", RFC 3264, June 2002.		Session Description Protocol (SDP)", RFC 3264, June 2002.
	skipping to change at page 15, line 8 ¶		skipping to change at page 13, line 8 ¶
	Parsippany, NJ 07054		Parsippany, NJ 07054
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