draft-ietf-speermint-architecture-17.txt		draft-ietf-speermint-architecture-18.txt
	SPEERMINT D. Malas, Ed.		SPEERMINT D. Malas, Ed.
	Internet-Draft CableLabs		Internet-Draft CableLabs
	Intended status: Informational J. Livingood, Ed.		Intended status: Informational J. Livingood, Ed.
	Expires: June 23, 2011 Comcast		Expires: August 21, 2011 Comcast
	December 20, 2010		February 17, 2011
	Session PEERing for Multimedia INTerconnect Architecture		Session PEERing for Multimedia INTerconnect Architecture
	draft-ietf-speermint-architecture-17		draft-ietf-speermint-architecture-18
	Abstract		Abstract
	This document defines a peering architecture for the Session		This document defines a peering architecture for the Session
	Initiation Protocol (SIP) [RFC3261], its functional components and		Initiation Protocol (SIP), its functional components and interfaces.
	interfaces. It also describes the components and the steps necessary		It also describes the components and the steps necessary to establish
	to establish a session between two SIP Service Provider (SSP) peering		a session between two SIP Service Provider (SSP) peering domains.
	domains.
	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 June 23, 2011.		This Internet-Draft will expire on August 21, 2011.
	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.
	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
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
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	Without obtaining an adequate license from the person(s) controlling		Without obtaining an adequate license from the person(s) controlling
	the copyright in such materials, this document may not be modified		the copyright in such materials, this document may not be modified
	outside the IETF Standards Process, and derivative works of it may		outside the IETF Standards Process, and derivative works of it may
	not be created outside the IETF Standards Process, except to format		not be created outside the IETF Standards Process, except to format
	it for publication as an RFC or to translate it into languages other		it for publication as an RFC or to translate it into languages other
	than English.		than English.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
	2. Reference Architecture . . . . . . . . . . . . . . . . . . . . 4		2. New Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
	3. Procedures of Inter-Domain SSP Session Establishment . . . . . 6		2.1. Session Border Controller (SBC) . . . . . . . . . . . . . 4
	4. Relationships Between Functions/Elements . . . . . . . . . . . 7		2.2. Carrier-of-Record . . . . . . . . . . . . . . . . . . . . 5
	5. Recommended SSP Procedures . . . . . . . . . . . . . . . . . . 7		3. Reference Architecture . . . . . . . . . . . . . . . . . . . . 5
	5.1. Originating or Indirect SSP Procedures . . . . . . . . . . 8		4. Procedures of Inter-Domain SSP Session Establishment . . . . . 7
	5.1.1. The Look-Up Function (LUF) . . . . . . . . . . . . . . 8		5. Relationships Between Functions/Elements . . . . . . . . . . . 8
	5.1.1.1. Target Address Analysis . . . . . . . . . . . . . 8		6. Recommended SSP Procedures . . . . . . . . . . . . . . . . . . 8
	5.1.1.2. ENUM Lookup . . . . . . . . . . . . . . . . . . . 9		6.1. Originating or Indirect SSP Procedures . . . . . . . . . . 8
	5.1.2. Location Routing Function (LRF) . . . . . . . . . . . 9		6.1.1. The Look-Up Function (LUF) . . . . . . . . . . . . . . 9
	5.1.2.1. DNS Resolution . . . . . . . . . . . . . . . . . . 9		6.1.1.1. Target Address Analysis . . . . . . . . . . . . . 9
	5.1.2.2. Routing Table . . . . . . . . . . . . . . . . . . 10		6.1.1.2. ENUM Lookup . . . . . . . . . . . . . . . . . . . 9
	5.1.2.3. LRF to LRF Routing . . . . . . . . . . . . . . . . 10		6.1.2. Location Routing Function (LRF) . . . . . . . . . . . 10
	5.1.3. The Signaling Path Border Element (SBE) . . . . . . . 10		6.1.2.1. DNS Resolution . . . . . . . . . . . . . . . . . . 10
	5.1.3.1. Establishing a Trusted Relationship . . . . . . . 10		6.1.2.2. Routing Table . . . . . . . . . . . . . . . . . . 10
	5.1.3.2. IPSec . . . . . . . . . . . . . . . . . . . . . . 10		6.1.2.3. LRF to LRF Routing . . . . . . . . . . . . . . . . 11
	5.1.3.3. Co-Location . . . . . . . . . . . . . . . . . . . 11		6.1.3. The Signaling Path Border Element (SBE) . . . . . . . 11
	5.1.3.4. Sending the SIP Request . . . . . . . . . . . . . 11		6.1.3.1. Establishing a Trusted Relationship . . . . . . . 11
	5.2. Target SSP Procedures . . . . . . . . . . . . . . . . . . 11		6.1.3.2. IPSec . . . . . . . . . . . . . . . . . . . . . . 11
	5.2.1. TLS . . . . . . . . . . . . . . . . . . . . . . . . . 11		6.1.3.3. Co-Location . . . . . . . . . . . . . . . . . . . 11
	5.2.2. Receive SIP Requests . . . . . . . . . . . . . . . . . 11		6.1.3.4. Sending the SIP Request . . . . . . . . . . . . . 12
	5.3. Data Path Border Element (DBE) . . . . . . . . . . . . . . 12		6.2. Target SSP Procedures . . . . . . . . . . . . . . . . . . 12
	6. Address Space Considerations . . . . . . . . . . . . . . . . . 12		6.2.1. TLS . . . . . . . . . . . . . . . . . . . . . . . . . 12
	7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12		6.2.2. Receive SIP Requests . . . . . . . . . . . . . . . . . 12
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12		6.3. Data Path Border Element (DBE) . . . . . . . . . . . . . . 12
	9. Security Considerations . . . . . . . . . . . . . . . . . . . 12		7. Address Space Considerations . . . . . . . . . . . . . . . . . 13
	10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 13		8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
	11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 14		9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
	12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15		10. Security Considerations . . . . . . . . . . . . . . . . . . . 13
	12.1. Normative References . . . . . . . . . . . . . . . . . . . 15		11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14
	12.2. Informative References . . . . . . . . . . . . . . . . . . 16		12. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 15
			13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16		13.1. Normative References . . . . . . . . . . . . . . . . . . . 16
			13.2. Informative References . . . . . . . . . . . . . . . . . . 18
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
	1. Introduction		1. Introduction
	This document defines a reference peering architecture for the		This document defines a reference peering architecture for the
	Session Initiation Protocol (SIP)[RFC3261], it's functional		Session Initiation Protocol (SIP)[RFC3261], it's functional
	components and interfaces, in the context of session peering for		components and interfaces, in the context of session peering for
	multimedia interconnects. In this process, we define the peering		multimedia interconnects. In this process, we define the peering
	reference architecture, its functional components, and peering		reference architecture, its functional components, and peering
	interface functions from the perspective of a SIP Service Provider's		interface functions from the perspective of a SIP Service Provider's
	(SSP) [RFC5486] network. Thus, it also describes the components and		(SSP) [RFC5486] network. Thus, it also describes the components and
	the steps necessary to establish a session between two SSP peering		the steps necessary to establish a session between two SSP peering
	domains.		domains.
			An SSP may also be referred to as an Internet Telephony Service
			Provider (ITSP). While the terms ITSP and SSP are frequently used
			interchangeably, this document and other subsequent SIP peering-
			related documents should use the term SSP. SSP more accurately
			depicts the use of SIP as the underlying layer 5 signaling protocol.
	This architecture enables the interconnection of two SSPs in layer 5		This architecture enables the interconnection of two SSPs in layer 5
	peering, as defined in the SIP-based session peering requirements		peering, as defined in the SIP-based session peering requirements
	[I-D.ietf-speermint-requirements].		[I-D.ietf-speermint-requirements].
	Layer 3 peering is outside the scope of this document. Hence, the		Layer 3 peering is outside the scope of this document. Hence, the
	figures in this document do not show routers so that the focus is on		figures in this document do not show routers so that the focus is on
	layer 5 protocol aspects.		layer 5 protocol aspects.
	This document uses terminology defined in the Session Peering for		This document uses terminology defined in the Session Peering for
	Multimedia Interconnect (SPEERMINT) Terminology document [RFC5486].		Multimedia Interconnect (SPEERMINT) Terminology document [RFC5486].
	Apart from normative references included herein, readers may also		Apart from normative references included herein, readers may also
	find [I-D.ietf-speermint-voip-consolidated-usecases] informative.		find [I-D.ietf-speermint-voip-consolidated-usecases] informative.
	2. Reference Architecture		2. New Terminology
			[RFC5486] is a key reference for the majority of the SPEERMINT-
			related terminology used in this document. However, some additional
			new terms are used here as follows in this section.
			2.1. Session Border Controller (SBC)
			A Session Border Controller (SBC) is referred to in Section 5. An
			SBC can contain a Signaling Function (SF), Signaling Path Border
			Element (SBE) and Data Path Border Element (DBE), and may perform the
			Look-Up Function (LUF) and Location Routing Function (LRF) functions,
			as described in Section 3. Whether the SBC performs one or more of
			these functions is generally speaking dependent upon how a SIP
			Service Provider (SSP) configures such a network element. In
			addition, requirements for an SBC can be found in [RFC5853].
			2.2. Carrier-of-Record
			A carrier-of-record, as used in Section 6.1.2.2, is defined in
			[RFC5067]. That document describes the term to refer to the entity
			having discretion over the domain and zone content and acting as the
			registrant for a telephone number, as represented in ENUM. This can
			be:
			o the Service Provider to which the E.164 number was allocated for
			end user assignment, whether by the National Regulatory Authority
			(NRA) or the International Telecommunication Union (ITU), for
			instance, a code under "International Networks" (+882) or
			"Universal Personal Telecommunications (UPT)" (+878) or,
			o if the number is ported, the service provider to which the number
			was ported, or
			o where numbers are assigned directly to end users, the service
			provider that the end user number assignee has chosen to provide a
			Public Switched Telephone Network/Public Land Mobile Network
			(PSTN/ PLMN) point-of-interconnect for the number.
			It is understood that the definition of carrier-of-record within a
			given jurisdiction is subject to modification by national
			authorities.
			3. Reference Architecture
	The following figure depicts the architecture and logical functions		The following figure depicts the architecture and logical functions
	that form peering between two SSPs.		that form peering between two SSPs.
	For further details on the elements and functions described in this		For further details on the elements and functions described in this
	figure, please refer to [RFC5486]. The following terms, which appear		figure, please refer to [RFC5486]. The following terms, which appear
	in Figure 1, which are documented in [RFC5486] are reproduced here		in Figure 1, which are documented in [RFC5486] are reproduced here
	for simplicity.		for simplicity.
	- Data Path Border Element (DBE): A data path border element (DBE) is		- Data Path Border Element (DBE): A data path border element (DBE) is
	skipping to change at page 5, line 49		skipping to change at page 6, line 51
	routing of SIP requests for establishing and maintaining calls, and		routing of SIP requests for establishing and maintaining calls, and
	to assist in the discovery or exchange of parameters to be used by		to assist in the discovery or exchange of parameters to be used by
	the Media Function (MF). The SF is a capability of SIP processing		the Media Function (MF). The SF is a capability of SIP processing
	elements such as SIP proxies, SBEs, and user agents.		elements such as SIP proxies, SBEs, and user agents.
	- SIP Service Provider (SSP): A SIP Service Provider (SSP) is an		- SIP Service Provider (SSP): A SIP Service Provider (SSP) is an
	entity that provides session services utilizing SIP signaling to its		entity that provides session services utilizing SIP signaling to its
	customers. In the event that the SSP is also a function of the SP,		customers. In the event that the SSP is also a function of the SP,
	it may also provide media streams to its customers. Such an SSP may		it may also provide media streams to its customers. Such an SSP may
	additionally be peered with other SSPs. An SSP may also interconnect		additionally be peered with other SSPs. An SSP may also interconnect
	with the PSTN. An SSP may also be referred to as an Internet		with the PSTN.
	Telephony Service Provider (ITSP). While the terms ITSP and SSP are
	frequently used interchangeably, this document and other subsequent
	SIP peering-related documents should use the term SSP. SSP more
	accurately depicts the use of SIP as the underlying layer 5 signaling
	protocol.
	+=============++ ++==============+		+=============++ ++=============+
	|| ||		|| ||
	+-----------+ +-----------+		+-----------+ +-----------+
	| SBE | +-----+ | SBE |		| SBE | +-----+ | SBE |
	| +-----+ | SIP |Proxy| | +-----+ |		| +-----+ | SIP |Proxy| | +-----+ |
	| | LUF |<-|------>|ENUM | | | LUF | |		| | LUF |<-|------>|ENUM | | | LUF | |
	| +-----+ | ENUM |TN DB| | +-----+ |		| +-----+ | ENUM |TN DB| | +-----+ |
	SIP | | +-----+ | |		SIP | | +-----+ | |
	------>| +-----+ | DNS +-----+ | +-----+ |		------>| +-----+ | DNS +-----+ | +-----+ |
	| | LRF |<-|------>|FQDN | | | LRF | |		| | LRF |<-|------>|FQDN | | | LRF | |
	| +-----+ | |IP | | +-----+ |		| +-----+ | |IP | | +-----+ |
	| +-----+ | SIP +-----+ | +-----+ |		| +-----+ | SIP +-----+ | +-----+ |
	| | SF |<-|----------------|->| SF | |		| | SF |<-|----------------|->| SF | |
	| +-----+ | | +-----+ |		| +-----+ | | +-----+ |
	+-----------+ +-----------+		+-----------+ +-----------+
	|| ||
	+-----------+ +-----------+
	RTP | DBE | RTP | DBE |
	------>| |--------------->| |
	+-----------+ +-----------+
	|| ||		|| ||
	SSP1 Network || || SSP2 Network		+-----------+ +-----------+
	+=============++ ++=============+		RTP | DBE | RTP | DBE |
			------>| |--------------->| |
			+-----------+ +-----------+
			|| ||
			SSP1 Network || || SSP2 Network
			+=============++ ++=============+
	Reference Architecture		Reference Architecture
	Figure 1		Figure 1
	3. Procedures of Inter-Domain SSP Session Establishment		4. Procedures of Inter-Domain SSP Session Establishment
	This document assumes that in order for a session to be established		This document assumes that in order for a session to be established
	from a User Agent (UA) in the originating (or indirect) SSP's network		from a User Agent (UA) in the originating (or indirect) SSP's network
	to an UA in the Target SSP's network the following steps are taken:		to an UA in the Target SSP's network the following steps are taken:
	1. Determine the target or indirect SSP via the LUF. (Note: If the		1. Determine the target or indirect SSP via the LUF. (Note: If the
	target address represents an intra-SSP resource, the behavior is		target address represents an intra-SSP resource, the behavior is
	out-of-scope with respect to this draft.)		out-of-scope with respect to this draft.)
	2. Determine the address of the SF of the target SSP via the LRF.		2. Determine the address of the SF of the target SSP via the LRF.
	3. Establish the session		3. Establish the session
	4. Exchange the media, which could include voice, video, text, etc.		4. Exchange the media, which could include voice, video, text, etc.
	5. End the session (BYE)		5. End the session (BYE)
			The originating or indirect SSP would perform steps 1-4, the target
	The originating or indirect SSP would likely perform steps 1-4, the		SSP would perform steps 4, and either one can perform step 5.
	target SSP would likely perform steps 4, and either one is likely to
	perform step 5.
	In the case the target SSP changes, then steps 1-4 would be repeated.		In the case the target SSP changes, then steps 1-4 would be repeated.
	This is reflected in Figure 1 that shows the target SSP with its own		This is reflected in Figure 1 that shows the target SSP with its own
	peering functions.		peering functions.
	4. Relationships Between Functions/Elements		5. Relationships Between Functions/Elements
	o An SBE can contain a SF function.		Please also refer to Figure 1.
	o An SF can perform LUF and LRF functions.		o An SBE can contain a Signaling Function (SF).
			o An SF can perform a Look-Up Function (LUF) and Location Routing
			Function (LRF).
	o As an additional consideration, a Session Border Controller, can		o As an additional consideration, a Session Border Controller, can
	contain an SF, SBE and DBE, and may perform the LUF and LRF		contain an SF, SBE and DBE, and may act as both an LUF and LRF.
	functions.
	o The following functions can communicate as follows, depending upon		o The following functions may communicate as follows in an example
	various real-world implementations:		SSP network, depending upon various real-world implementations:
	* SF can communicate with LUF, LRF, SBE and SF		* SF may communicate with LUF, LRF, SBE and SF
	* LUF can communicator with SF and SBE		* LUF may communicate with SF and SBE
	* LRF can communicate with SF and SBE		* LRF may communicate with SF and SBE
	5. Recommended SSP Procedures		6. Recommended SSP Procedures
	This section describes the functions in more detail and provides some		This section describes the functions in more detail and provides some
	recommendations on the role they would play in a SIP call in a Layer		recommendations on the role they would play in a SIP call in a Layer
	5 peering scenario.		5 peering scenario.
	Some of the information in the section is taken from		Some of the information in the section is taken from
	[I-D.ietf-speermint-requirements] and is put here for continuity		[I-D.ietf-speermint-requirements] and is included here for continuity
	purposes.		purposes. It is also important to refer to Section 3.2 of
			[I-D.ietf-speermint-voipthreats], particularly with respect to the
			use of IPSec and TLS.
	5.1. Originating or Indirect SSP Procedures		6.1. Originating or Indirect SSP Procedures
	This section describes the procedures of the originating or indirect		This section describes the procedures of the originating or indirect
	SSP.		SSP.
	5.1.1. The Look-Up Function (LUF)		6.1.1. The Look-Up Function (LUF)
	The purpose of the LUF is to determine the SF of the target domain of		The purpose of the LUF is to determine the SF of the target domain of
	a given request and optionally to develop Session Establishment Data.		a given request and optionally to develop Session Establishment Data.
	It is important to note that the LUF may utilize the public e164.arpa		It is important to note that the LUF may utilize the public e164.arpa
	ENUM root, as well as one or more private roots. When private roots		ENUM root, as well as one or more private roots. When private roots
	are used specialized routing rules may be implemented, and these		are used specialized routing rules may be implemented, and these
	rules may vary depending upon whether an originating or indirect SSP		rules may vary depending upon whether an originating or indirect SSP
	is querying the LUF.		is querying the LUF.
	5.1.1.1. Target Address Analysis		6.1.1.1. Target Address Analysis
	When the originating (or indirect) SSP receives a request to		When the originating (or indirect) SSP receives a request to
	communicate, it analyzes the target URI to determine whether the call		communicate, it analyzes the target URI to determine whether the call
	needs to be routed internal or external to its network. The analysis		needs to be routed internal or external to its network. The analysis
	method is internal to the SSP; thus, outside the scope of SPEERMINT.		method is internal to the SSP; thus, outside the scope of SPEERMINT.
	If the target address does not represent a resource inside the		If the target address does not represent a resource inside the
	originating (or indirect) SSP's administrative domain or federation		originating (or indirect) SSP's administrative domain or federation
	of domains, then the originating (or indirect) SSP performs a Lookup		of domains, then the originating (or indirect) SSP performs a Lookup
	Function (LUF) to determine a target address, and then is resolves		Function (LUF) to determine a target address, and then it resolves
	the call routing data by using the Location routing Function (LRF).		the call routing data by using the Location routing Function (LRF).
	For example, if the request to communicate is for an im: or pres: URI		For example, if the request to communicate is for an im: or pres: URI
	type [RFC3861] [RFC3953], the originating (or indirect) SSP follows		type [RFC3861] [RFC3953], the originating (or indirect) SSP follows
	the procedures in [RFC3861]. If the highest priority supported URI		the procedures in [RFC3861]. If the highest priority supported URI
	scheme is sip: or sips: the originating (or indirect) SSP skips to		scheme is sip: or sips: the originating (or indirect) SSP skips to
	SIP DNS resolution in Section 5.1.3. Likewise, if the target address		SIP DNS resolution in Section 5.1.3. Likewise, if the target address
	is already a sip: or sips: URI in an external domain, the originating		is already a sip: or sips: URI in an external domain, the originating
	(or indirect) SSP skips to SIP DNS resolution in Section 5.1.2.1.		(or indirect) SSP skips to SIP DNS resolution in Section 6.1.2.1.
	This may be the case, to use one example, with		This may be the case, to use one example, with
	"sips:bob@biloxi.example.com".		"sips:bob@biloxi.example.com".
	If the target address corresponds to a specific E.164 address, the		If the target address corresponds to a specific E.164 address, the
	SSP may need to perform some form of number plan mapping according to		SSP may need to perform some form of number plan mapping according to
	local policy. For example, in the United States, a dial string		local policy. For example, in the United States, a dial string
	beginning "011 44" could be converted to "+44", or in the United		beginning "011 44" could be converted to "+44", or in the United
	Kingdom "00 1" could be converted to "+1". Once the SSP has an E.164		Kingdom "00 1" could be converted to "+1". Once the SSP has an E.164
	address, it can use ENUM.		address, it can use ENUM.
	5.1.1.2. ENUM Lookup		6.1.1.2. ENUM Lookup
	If an external E.164 address is the target, the originating (or		If an external E.164 address is the target, the originating (or
	indirect) SSP consults the public "User ENUM" rooted at e164.arpa,		indirect) SSP consults the public "User ENUM" rooted at e164.arpa,
	according to the procedures described in [RFC3761]. The SSP must		according to the procedures described in [RFC3761]. The SSP must
	query for the "E2U+sip" enumservice as described in [RFC3764], but		query for the "E2U+sip" enumservice as described in [RFC3764], but
	may check for other enumservices. The originating (or indirect) SSP		may check for other enumservices. The originating (or indirect) SSP
	may consult a cache or alternate representation of the ENUM data		may consult a cache or alternate representation of the ENUM data
	rather than actual DNS queries. Also, the SSP may skip actual DNS		rather than actual DNS queries. Also, the SSP may skip actual DNS
	queries if the originating (or indirect) SSP is sure that the target		queries if the originating (or indirect) SSP is sure that the target
	address country code is not represented in e164.arpa.		address country code is not represented in e164.arpa.
	If an im: or pres: URI is chosen based on an "E2U+im" [RFC3861] or		If an im: or pres: URI is chosen based on an "E2U+im" [RFC3861] or
	"E2U+pres" [RFC3953] enumserver, the SSP follows the procedures for		"E2U+pres" [RFC3953] enumserver, the SSP follows the procedures for
	resolving these URIs to URIs for specific protocols such a SIP or		resolving these URIs to URIs for specific protocols such as SIP or
	XMPP as described in the previous section.		XMPP as described in the previous section.
	The NAPTR response to the ENUM lookup may be a SIP AoR (such as		The NAPTR response to the ENUM lookup may be a SIP AoR (such as
	"sips:bob@example.com") or SIP URI (such as		"sips:bob@example.com") or SIP URI (such as
	"sips:bob@sbe1.biloxi.example.com"). In the case of when a SIP URI		"sips:bob@sbe1.biloxi.example.com"). In the case of when a SIP URI
	is returned, the originating (or indirect) SSP has sufficient routing		is returned, the originating (or indirect) SSP has sufficient routing
	information to locate the target SSP. In the case of when a SIP AoR		information to locate the target SSP. In the case of when a SIP AoR
	is returned, the SF then uses the LRF to determine the URI for more		is returned, the SF then uses the LRF to determine the URI for more
	explicitly locating the target SSP.		explicitly locating the target SSP.
	5.1.2. Location Routing Function (LRF)		6.1.2. Location Routing Function (LRF)
	The LRF of an originating (or indirect) SSP analyzes target address		The LRF of an originating (or indirect) SSP analyzes target address
	and target domain identified by the LUF, and discovers the next hop		and target domain identified by the LUF, and discovers the next hop
	signaling function (SF) in a peering relationship. The resource to		signaling function (SF) in a peering relationship. The resource to
	determine the SF of the target domain might be provided by a third-		determine the SF of the target domain might be provided by a third-
	party as in the assisted-peering case. The following sections define		party as in the assisted-peering case. The following sections define
	mechanisms which may be used by the LRF. These are not in any		mechanisms which may be used by the LRF. These are not in any
	particular order and, importantly, not all of them may be used.		particular order and, importantly, not all of them have to be used.
	5.1.2.1. DNS Resolution		6.1.2.1. DNS Resolution
	The originating (or indirect) SSP uses the procedures in Section 4 of		The originating (or indirect) SSP uses the procedures in Section 4 of
	[RFC3263] to determine how to contact the receiving SSP. To		[RFC3263] to determine how to contact the receiving SSP. To
	summarize the [RFC3263] procedure: unless these are explicitly		summarize the [RFC3263] procedure: unless these are explicitly
	encoded in the target URI, a transport is chosen using NAPTR records,		encoded in the target URI, a transport is chosen using NAPTR records,
	a port is chosen using SRV records, and an address is chosen using A		a port is chosen using SRV records, and an address is chosen using A
	or AAAA records.		or AAAA records.
	When communicating with another SSP, entities compliant to this		When communicating with another SSP, entities compliant to this
	document should select a TLS-protected transport for communication		document should select a TLS-protected transport for communication
	from the originating (or indirect) SSP to the receiving SSP if		from the originating (or indirect) SSP to the receiving SSP if
	available, as described further in Section 5.2.1.		available, as described further in Section 6.2.1.
	5.1.2.2. Routing Table		6.1.2.2. Routing Table
	If there are no End User ENUM records and the originating (or		If there are no End User ENUM records and the originating (or
	indirect) SSP cannot discover the carrier-of-record or if the		indirect) SSP cannot discover the carrier-of-record or if the
	originating (or indirect) SSP cannot reach the carrier-of-record via		originating (or indirect) SSP cannot reach the carrier-of-record via
	SIP peering, the originating (or indirect) SSP may deliver the call		SIP peering, the originating (or indirect) SSP may deliver the call
	to the PSTN or reject it. Note that the originating (or indirect)		to the PSTN or reject it. Note that the originating (or indirect)
	SSP may forward the call to another SSP for PSTN gateway termination		SSP may forward the call to another SSP for PSTN gateway termination
	by prior arrangement using the routing table.		by prior arrangement using the local SIP proxy routing table.
	If so, the originating (or indirect) SSP rewrites the Request-URI to		If so, the originating (or indirect) SSP rewrites the Request-URI to
	address the gateway resource in the target SSP's domain and may		address the gateway resource in the target SSP's domain and may
	forward the request on to that SSP using the procedures described in		forward the request on to that SSP using the procedures described in
	the remainder of these steps.		the remainder of these steps.
	5.1.2.3. LRF to LRF Routing		6.1.2.3. LRF to LRF Routing
	Communications between the LRF of two interconnecting SSPs may use		Communications between the LRF of two interconnecting SSPs may use
	DNS or statically provisioned IP Addresses for reachability. Other		DNS or statically provisioned IP Addresses for reachability. Other
	inputs to determine the path may be code-based routing, method-based		inputs to determine the path may be code-based routing, method-based
	routing, Time of day, least cost and/or source-based routing.		routing, Time of day, least cost and/or source-based routing.
	5.1.3. The Signaling Path Border Element (SBE)		6.1.3. The Signaling Path Border Element (SBE)
	The purpose of signaling function is to perform routing of SIP		The purpose of signaling function is to perform routing of SIP
	messages as well as optionally implement security and policies on SIP		messages as well as optionally implement security and policies on SIP
	messages, and to assist in discovery/exchange of parameters to be		messages, and to assist in discovery/exchange of parameters to be
	used by the Media Function (MF). The signaling function performs the		used by the Media Function (MF). The signaling function performs the
	routing of SIP messages. The SBE may be a B2BUA or it may act as a		routing of SIP messages. The SBE may be a B2BUA or it may act as a
	SIP proxy. Optionally, a SF may perform additional functions such as		SIP proxy. Optionally, an SF may perform additional functions such
	Session Admission Control, SIP Denial of Service protection, SIP		as Session Admission Control, SIP Denial of Service protection, SIP
	Topology Hiding, SIP header normalization, SIP security, privacy, and		Topology Hiding, SIP header normalization, SIP security, privacy, and
	encryption. The SF of a SBE can also process SDP payloads for media		encryption. The SF of an SBE can also process SDP payloads for media
	information such as media type, bandwidth, and type of codec; then,		information such as media type, bandwidth, and type of codec; then,
	communicate this information to the media function.		communicate this information to the media function.
	5.1.3.1. Establishing a Trusted Relationship		6.1.3.1. Establishing a Trusted Relationship
	Depending on the security needs and trust relationships between SSPs,		Depending on the security needs and trust relationships between SSPs,
	different security mechanism can be used to establish SIP calls.		different security mechanisms can be used to establish SIP calls.
	These are discussed in the following subsections.		These are discussed in the following subsections.
	5.1.3.2. IPSec		6.1.3.2. IPSec
	In certain deployments the use of IPSec between the signaling		In certain deployments the use of IPSec between the signaling
	functions of the originating and terminating domains can be used as a		functions of the originating and terminating domains can be used as a
	security mechanism instead of TLS.		security mechanism instead of TLS.
	5.1.3.3. Co-Location		6.1.3.3. Co-Location
	In this scenario the SFs are co-located in a physically secure		In this scenario the SFs are co-located in a physically secure
	location and/or are members of a segregated network. In this case		location and/or are members of a segregated network. In this case
	messages between the originating and terminating SSPs would be sent		messages between the originating and terminating SSPs could be sent
	as clear text.		as clear text (unencrypted). However, even in these semi-trusted co-
			location facilities, other security or access control mechanisms may
			be appropriate, such as IP access control lists or other mechanisms.
	5.1.3.4. Sending the SIP Request		6.1.3.4. Sending the SIP Request
	Once a trust relationship between the peers is established, the		Once a trust relationship between the peers is established, the
	originating (or indirect) SSP sends the request.		originating (or indirect) SSP sends the request.
	5.2. Target SSP Procedures		6.2. Target SSP Procedures
	This section describes the Target SSP Procedures.		This section describes the Target SSP Procedures.
	5.2.1. TLS		6.2.1. TLS
	The section defines uses of TLS between two SSPs [RFC5246] [RFC5746]		The section defines the usage of TLS between two SSPs [RFC5246]
	[RFC5878]. When the receiving SSP receives a TLS client hello, it		[RFC5746] [RFC5878]. When the receiving SSP receives a TLS client
	responds with its certificate. The Target SSP certificate should be		hello, it responds with its certificate. The Target SSP certificate
	valid and rooted in a well-known certificate authority. The		should be valid and rooted in a well-known certificate authority.
	procedures to authenticate the SSP's originating domain are specified		The procedures to authenticate the SSP's originating domain are
	in [RFC5922].		specified in [RFC5922].
	The SF of the Target SSP verifies that the Identity header is valid,		The SF of the Target SSP verifies that the Identity header is valid,
	corresponds to the message, corresponds to the Identity-Info header,		corresponds to the message, corresponds to the Identity-Info header,
	and that the domain in the From header corresponds to one of the		and that the domain in the From header corresponds to one of the
	domains in the TLS client certificate.		domains in the TLS client certificate.
	5.2.2. Receive SIP Requests		As noted above in Section 6.1.3.2, some deployments may utilize IPSec
			rather than TLS.
			6.2.2. Receive SIP Requests
	Once a trust relationship is established, the Target SSP is prepared		Once a trust relationship is established, the Target SSP is prepared
	to receive incoming SIP requests. For new requests (dialog forming		to receive incoming SIP requests. For new requests (dialog forming
	or not) the receiving SSP verifies if the target (request-URI) is a		or not) the receiving SSP verifies if the target (request-URI) is a
	domain that for which it is responsible. For these requests, there		domain that for which it is responsible. For these requests, there
	should be no remaining Route header field values. For in-dialog		should be no remaining Route header field values. For in-dialog
	requests, the receiving SSP can verify that it corresponds to the		requests, the receiving SSP can verify that it corresponds to the
	top-most Route header field value.		top-most Route header field value.
	The receiving SSP may reject incoming requests due to local policy.		The receiving SSP may reject incoming requests due to local policy.
	When a request is rejected because the originating (or indirect) SSP		When a request is rejected because the originating (or indirect) SSP
	is not authorized to peer, the receiving SSP should respond with a		is not authorized to peer, the receiving SSP should respond with a
	403 response with the reason phrase "Unsupported Peer".		403 response with the reason phrase "Unsupported Peer".
	5.3. Data Path Border Element (DBE)		6.3. Data Path Border Element (DBE)
	The purpose of the DBE [RFC5486] is to perform media related		The purpose of the DBE [RFC5486] is to perform media related
	functions such as media transcoding and media security implementation		functions such as media transcoding and media security implementation
	between two SSPs.		between two SSPs.
	An example of this is to transform a voice payload from one codec		An example of this is to transform a voice payload from one codec
	(e.g., G.711) to another (e.g., EvRC). Additionally, the MF may		(e.g., G.711) to another (e.g., EvRC). Additionally, the MF may
	perform media relaying, media security [RFC3711], privacy, and		perform media relaying, media security [RFC3711], privacy, and
	encryption.		encryption.
	6. Address Space Considerations		7. Address Space Considerations
	Peering must occur in a common IP address space, which is defined by		Peering must occur in a common IP address space, which is defined by
	the federation, which may be entirely on the public Internet, or some		the federation, which may be entirely on the public Internet, or some
	private address space [RFC1918]. The origination or termination		private address space [RFC1918]. The origination or termination
	networks may or may not entirely be in the same address space. If		networks may or may not entirely be in the same address space. If
	they are not, then a network address translation (NAT) or similar may		they are not, then a network address translation (NAT) or similar may
	be needed before the signaling or media is presented correctly to the		be needed before the signaling or media is presented correctly to the
	federation. The only requirement is that all associated entities		federation. The only requirement is that all associated entities
	across the peering interface are reachable.		across the peering interface are reachable.
	7. Acknowledgments		8. Acknowledgments
	The working group would like to thank John Elwell, Otmar Lendl, Rohan		The working group would like to thank John Elwell, Otmar Lendl, Rohan
	Mahy, Alexander Mayrhofer, Jim McEachern, Jean-Francois Mule,		Mahy, Alexander Mayrhofer, Jim McEachern, Jean-Francois Mule,
	Jonathan Rosenberg, and Dan Wing for their valuable contributions to		Jonathan Rosenberg, and Dan Wing for their valuable contributions to
	various versions of this document.		various versions of this document.
	8. IANA Considerations		9. IANA Considerations
	This memo includes no request to IANA.		This memo includes no request to IANA.
	9. Security Considerations		10. Security Considerations
	In all cases, cryptographic-based security should be maintained as an		The level (or types) of security mechanisms implemented between
	optional requirement between peering providers conditioned on the		peering providers is in practice dependent upon on the underlying
	presence or absence of underlying physical security of SSP		physical security of SSP connections. This means, as noted in
	connections, e.g. within the same secure physical building.		Section 6.1.3.3, whether peering equipment is in a secure facility or
			not may bear on other types of security mechanisms which may be
			appropriate. Thus, if two SSPs peered across public Internet links,
			they are likely to use IPSec or TLS since the link between the two
			domains should be considered untrusted.
	In order to maintain a consistent approach, unique and specialized		Many detailed and highly relevant security requirements for SPEERMINT
	security requirements common for the majority of peering		have been documented in Section 5 of
	relationships, should be standardized within the IETF. These		[I-D.ietf-speermint-requirements]. As a result, that document should
	standardized methods may enable capabilities such as dynamic peering		be considered required reading.
	relationships across publicly maintained interconnections.
	Additional security considerations have been documented separately in		Additional and important security considerations have been documented
	[I-D.ietf-speermint-voipthreats].		separately in [I-D.ietf-speermint-voipthreats]. This document
			describes the many relevant security threats to SPEERMINT, as well
			the relevant countermeasures and security protections which are
			recommended to combat any potential threats or other risks. This
			includes a wide range of detailed threats in Section 2 of
			[I-D.ietf-speermint-voipthreats]. It also includes key requirements
			in Section 3.1 of [I-D.ietf-speermint-voipthreats], such as the
			requirement for the LUF and LRF to support mutual authentication for
			queries, among other requirements which are related to
			[I-D.ietf-speermint-requirements]. Section 3.2 of
			[I-D.ietf-speermint-voipthreats] explains how to meet these security
			requirements, and then Section 4 explores a wide range of suggested
			countermeasures.
	10. Contributors		11. Contributors
	Mike Hammer		Mike Hammer
	Cisco Systems		Cisco Systems
	Herndon, VA - USA		Herndon, VA - USA
	Email: mhammer@cisco.com		Email: mhammer@cisco.com
	--------------------------------------------------------------		--------------------------------------------------------------
	skipping to change at page 14, line 32		skipping to change at page 15, line 40
	--------------------------------------------------------------		--------------------------------------------------------------
	Adam Uzelac		Adam Uzelac
	Global Crossing		Global Crossing
	Rochester, NY - USA		Rochester, NY - USA
	Email: adam.uzelac@globalcrossing.com		Email: adam.uzelac@globalcrossing.com
	11. Change Log		12. Change Log
	NOTE TO RFC EDITOR: PLEASE REMOVE THIS SECTION PRIOR TO PUBLICATION.		NOTE TO RFC EDITOR: PLEASE REMOVE THIS SECTION PRIOR TO PUBLICATION.
			o 18: Made several changes based on feedback from Adrian Farrel,
			Bert Wijnen, Dan Romascanu, Avshalom Houri, Russ Housley, Sean
			Turner, Tim Polk, and Russ Mundy during IESG review.
	o 17: Misc. updates at the request of Gonzalo, the RAI AD, in order		o 17: Misc. updates at the request of Gonzalo, the RAI AD, in order
	to clear his review and move to the IESG. This included adding		to clear his review and move to the IESG. This included adding
	terminology from RFC 5486 and expanding the document name.		terminology from RFC 5486 and expanding the document name.
	o 16: Yes, one final outdated reference to fix.		o 16: Yes, one final outdated reference to fix.
	o 15: Doh! Uploaded the wrong doc to create -14. Trying again. :-)		o 15: Doh! Uploaded the wrong doc to create -14. Trying again. :-)
	o 14: WGLC ended. Ran final nits check prior to sending proto to		o 14: WGLC ended. Ran final nits check prior to sending proto to
	the AD and sending the doc to the IESG. Found a few very minor		the AD and sending the doc to the IESG. Found a few very minor
	skipping to change at page 15, line 15		skipping to change at page 16, line 25
	o 13: Closed out all remaining tickets, resolved all editorial		o 13: Closed out all remaining tickets, resolved all editorial
	notes.		notes.
	o 12: Closed out several open issues. Properly XML-ized all		o 12: Closed out several open issues. Properly XML-ized all
	references. Updated contributors list.		references. Updated contributors list.
	o 11: Quick update to refresh the I-D since it expired, and cleaned		o 11: Quick update to refresh the I-D since it expired, and cleaned
	up some of the XML for references. A real revision is coming		up some of the XML for references. A real revision is coming
	soon.		soon.
	12. References		13. References
	12.1. Normative References		13.1. Normative References
	[I-D.ietf-speermint-requirements]		[I-D.ietf-speermint-requirements]
	Mule, J., "Requirements for SIP-based Session Peering",		Mule, J., "Requirements for SIP-based Session Peering",
	draft-ietf-speermint-requirements-10 (work in progress),		draft-ietf-speermint-requirements-10 (work in progress),
	October 2010.		October 2010.
	[I-D.ietf-speermint-voipthreats]		[I-D.ietf-speermint-voipthreats]
	Seedorf, J., Niccolini, S., Chen, E., and H. Scholz,		Seedorf, J., Niccolini, S., Chen, E., and H. Scholz,
	"Session Peering for Multimedia Interconnect (SPEERMINT)		"Session Peering for Multimedia Interconnect (SPEERMINT)
	Security Threats and Suggested Countermeasures",		Security Threats and Suggested Countermeasures",
	draft-ietf-speermint-voipthreats-06 (work in progress),		draft-ietf-speermint-voipthreats-07 (work in progress),
	November 2010.		January 2011.
	[RFC1035] Mockapetris, P., "Domain names - implementation and		[RFC1035] Mockapetris, P., "Domain names - implementation and
	specification", STD 13, RFC 1035, November 1987.		specification", STD 13, RFC 1035, November 1987.
	[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and		[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
	E. Lear, "Address Allocation for Private Internets",		E. Lear, "Address Allocation for Private Internets",
	BCP 5, RFC 1918, February 1996.		BCP 5, RFC 1918, February 1996.
	[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.
	skipping to change at page 16, line 18		skipping to change at page 17, line 28
	Initiation Protocol (SIP) Addresses-of-Record", RFC 3764,		Initiation Protocol (SIP) Addresses-of-Record", RFC 3764,
	April 2004.		April 2004.
	[RFC3861] Peterson, J., "Address Resolution for Instant Messaging		[RFC3861] Peterson, J., "Address Resolution for Instant Messaging
	and Presence", RFC 3861, August 2004.		and Presence", RFC 3861, August 2004.
	[RFC3953] Peterson, J., "Telephone Number Mapping (ENUM) Service		[RFC3953] Peterson, J., "Telephone Number Mapping (ENUM) Service
	Registration for Presence Services", RFC 3953,		Registration for Presence Services", RFC 3953,
	January 2005.		January 2005.
			[RFC5067] Lind, S. and P. Pfautz, "Infrastructure ENUM
			Requirements", RFC 5067, November 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.
	[RFC5486] Malas, D. and D. Meyer, "Session Peering for Multimedia		[RFC5486] Malas, D. and D. Meyer, "Session Peering for Multimedia
	Interconnect (SPEERMINT) Terminology", RFC 5486,		Interconnect (SPEERMINT) Terminology", RFC 5486,
	March 2009.		March 2009.
	[RFC5746] Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,		[RFC5746] Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,
	"Transport Layer Security (TLS) Renegotiation Indication		"Transport Layer Security (TLS) Renegotiation Indication
	Extension", RFC 5746, February 2010.		Extension", RFC 5746, February 2010.
			[RFC5853] Hautakorpi, J., Camarillo, G., Penfield, R., Hawrylyshen,
			A., and M. Bhatia, "Requirements from Session Initiation
			Protocol (SIP) Session Border Control (SBC) Deployments",
			RFC 5853, April 2010.
	[RFC5878] Brown, M. and R. Housley, "Transport Layer Security (TLS)		[RFC5878] Brown, M. and R. Housley, "Transport Layer Security (TLS)
	Authorization Extensions", RFC 5878, May 2010.		Authorization Extensions", RFC 5878, May 2010.
	[RFC5922] Gurbani, V., Lawrence, S., and A. Jeffrey, "Domain		[RFC5922] Gurbani, V., Lawrence, S., and A. Jeffrey, "Domain
	Certificates in the Session Initiation Protocol (SIP)",		Certificates in the Session Initiation Protocol (SIP)",
	RFC 5922, June 2010.		RFC 5922, June 2010.
	12.2. Informative References		13.2. Informative References
	[I-D.ietf-speermint-voip-consolidated-usecases]		[I-D.ietf-speermint-voip-consolidated-usecases]
	Uzelac, A. and Y. Lee, "VoIP SIP Peering Use Cases",		Uzelac, A. and Y. Lee, "VoIP SIP Peering Use Cases",
	draft-ietf-speermint-voip-consolidated-usecases-18 (work		draft-ietf-speermint-voip-consolidated-usecases-18 (work
	in progress), April 2010.		in progress), April 2010.
	[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.
End of changes. 67 change blocks.
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