draft-ietf-speermint-architecture-09.txt		draft-ietf-speermint-architecture-10.txt
	Speermint Working Group A.Uzelac(Ed.)
	Internet Draft Global Crossing
	Intended status: Informational
	Expires: May 2010
	November 10, 2009
	SPEERMINT Peering Architecture		SPEERMINT A. Uzelac, Ed.
	draft-ietf-speermint-architecture-09		Internet-Draft Global Crossing
			Intended status: Informational R. Penno
			Expires: September 10, 2010 Juniper Networks
			M. Hammer
			Cisco Systems
			D. Malas
			CableLabs
			S. Khan
			Comcast
			H. Kaplan
			Acme Packet
			J. Livingood
			Comcast
			D. Schwartz
			XConnect Global Networks
			R. Shockey
			Shockey Consulting
			March 9, 2010
			SPEERMINT Peering Architecture
			draft-ietf-speermint-architecture-10
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			Abstract
			This document defines a peering architecture for the Session
			Initation Protocol (SIP) [RFC3261], it's functional components and
			interfaces. It also describes the steps necessary to establish a
			session between two peering domains in the context of the functions
			defined.
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	Abstract
	This document defines the SPEERMINT peering architecture, its functional
	components and peering interface functions. It also describes the steps taken
	to establish a session between two peering domains in the context of the
	functions defined.
	Table of Contents		Table of Contents
	1. Introduction...................................................2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
	2. Reference SPEERMINT Architecture...............................4		2. Reference Architecture . . . . . . . . . . . . . . . . . . . . 4
	3. Procedures of Inter-domain SSP Session Establishment...........4		3. Procedures of Inter-domain SSP Session Establishment . . . . . 5
	3.1. Relationships between functions/elements..................5		4. Relationships between functions/elements . . . . . . . . . . . 6
	4. Recommended SSP Procedures.....................................5		5. Recommended SSP Procedures . . . . . . . . . . . . . . . . . . 6
	4.1. Originating SSP Procedures................................5		5.1. Originating SSP Procedures . . . . . . . . . . . . . . . . 7
	4.1.1. The Look-Up Function (LUF)...........................5		5.1.1. The Look-Up Function (LUF) . . . . . . . . . . . . . . 7
	4.1.1.1. Target Address Analysis.........................6		5.1.1.1. Target Address Analysis . . . . . . . . . . . . . 7
	4.1.1.2. ENUM Lookup.....................................6		5.1.1.2. ENUM Lookup . . . . . . . . . . . . . . . . . . . 7
	4.1.2. Location Routing Function (LRF)......................6		5.1.2. Location Routing Function (LRF) . . . . . . . . . . . 8
	4.1.2.1. DNS Resolution..................................7		5.1.2.1. DNS resolution . . . . . . . . . . . . . . . . . . 8
	4.1.2.2. Routing Table...................................7		5.1.2.2. Routing Table . . . . . . . . . . . . . . . . . . 8
	4.1.2.3. LRF to LRF Routing..............................7		5.1.2.3. LRF to LRF Routing . . . . . . . . . . . . . . . . 8
	4.1.3. The Signaling Path Border Element (SBE)..............7		5.1.3. Signaling Path Border Element (SBE) . . . . . . . . . 8
	4.1.3.1. Establishing a Trusted Relationship.............8		5.1.4. Establishing a Trusted Relationship . . . . . . . . . 9
	4.1.3.2. Sending the SIP request.........................8		5.1.4.1. IPSec . . . . . . . . . . . . . . . . . . . . . . 9
	4.2. Target SSP Procedures.....................................8		5.1.4.2. Co-Location . . . . . . . . . . . . . . . . . . . 9
	4.2.1. The Ingress Signaling Path Border Element (SBE)......8		5.1.4.3. Sending the SIP Request . . . . . . . . . . . . . 9
	4.2.1.1. TLS.............................................8		5.2. Target SSP Procedures . . . . . . . . . . . . . . . . . . 9
	4.2.1.2. Receive SIP requests............................9		5.2.1. The Ingress SBE . . . . . . . . . . . . . . . . . . . 10
	4.3. Data Path Border Element (DBE)............................9		5.2.1.1. TLS . . . . . . . . . . . . . . . . . . . . . . . 10
	5. Address space considerations...................................9		5.2.1.2. Receive SIP Requests . . . . . . . . . . . . . . . 10
	6. Security Considerations........................................9		5.3. Data Path Border Element (DBE) . . . . . . . . . . . . . . 10
	7. IANA Considerations...........................................10		6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
	8. Acknowledgments...............................................10		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
	9. References....................................................11		8. Security Considerations . . . . . . . . . . . . . . . . . . . 11
	9.1. Normative References.....................................11		9. Normative References . . . . . . . . . . . . . . . . . . . . . 11
	9.2. Informative References...................................12		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
	Author's Addresses...............................................13
	1. Introduction
	The objective of this document is to define a reference peering architecture in
	the context of Session PEERing for Multimedia INTerconnect (SPEERMINT). In this
	process, we define the peering reference architecture, its functional
	components, and peering interface functions from the perspective of a SIP
	Service provider's (SSP) network.
	This architecture allows the interconnection of two SSPs in layer 5 peering as
	defined in the SPEERMINT Requirements [14] and Terminology [13] documents.
	Layer 3 peering is outside the scope of this document. Hence, the figures in		1. Introduction
	this document do not show routers so that the focus is on Layer 5 protocol
	aspects.
	This document uses terminology defined in the SPEERMINT Terminology document		The objective of this document is to define a reference peering
	[13], so the reader should be familiar with all the terms defined there.		architecture in the context of session peering for multimedia
			interconnects. In this process, we define the peering reference
			architecture, its functional components, and peering interface
			functions from the perspective of a SIP Service provider's (SSP)
			[RFC5486] network.
	In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL",		This architecture allows the interconnection of two SSPs in layer 5
	"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are		peering as defined in the SIP-based session peering requirements
	to be interpreted as described in [RFC2119].		[I-D.ietf-speermint-requirements].
	2. Reference SPEERMINT Architecture		Layer 3 peering is outside the scope of this document. Hence, the
			figures in this document focus on Layer 5 protocol functions and
			elements.
	Figure 2 depicts the SPEERMINT architecture and logical functions that form the		This document uses terminology defined in the Session Peering for
	peering between two SSPs.		Multimedia Interconnect Terminology document [RFC5486].
	--------------- ---------------		2. Reference Architecture
	/ \ / \
	| +--LUF-+ | +------+ | +--LUF-+ |
	| |->| | | | ENUM | | | |<-| |
	| | | +------------>| TN DB|<------------+ | | |
	| | | | | +------+ | | | | |
	| | +------+ | | +------+ | |
	| | | | | |
	| | +--LRF-+ | +--------+ | +--LRF-+ | |
	| |->| | | | DNS | | | |<-| |
	| | | +----------->|IP Addrs|<-----------+ | | |
	| | | | | +--------+ | | | | |
	| | +------+ | | +------+ | |
	| | | | | |
	| | | | | |
	| | +-------+ +-------+ | |
	| ----------->| | | |<----------- |
	| | SBE |<------------>| SBE | |
	| | | | | |
	| +-------+ +-------+ |
	| SSP1 | | SSP2 |
	| +-------+ +-------+ |
	| | | | | |
	| | DBE |<------------>| DBE | |
	| | | | | |
	| +-------+ +-------+ |
	\ / \ /
	--------------- ---------------
	Figure 1: Reference SPEERMINT Architecture
	For further details on the elements and functions described in this figure,		Figure 1 depicts the architecture and logical functions that form
	please refer to [RFC 5486].		peering between two SSPs. The terms used in the diagram are expanded
			here for reference:
	3. Procedures of Inter-domain SSP Session Establishment		o SBE - Signaling Path Border Element is described in Section 5.1.3
	This document assumes that in order for a session to be established from a UA		o LUF - Look-up Function is described in Section 5.1.1
	in the Originating SSP's network to an UA in the Target SSP's network the
	following steps are taken:
	1. Determine the target SSP via the LUF.		o LRF - Location Routing Function is described in Section 5.1.2
	a. If the target address represents an intra-SSP resource, the		o SF - Signaling Function is defined in [RFC5486]
	behavior is out-of-scope with respect to this draft.
	2. Determine the address of the SF of the target SSP via the LRF.		o SIP - Session Initiation Protocol is defined in [RFC3261]
	3. Establish the session		o DBE - Data Path Border Element is described in Section 5.3
	4. Exchange the media, which could include voice, video, tec, etc.		o DNS - Domain Name Service is described in Section 5.1.2.1
	5. End the session (BYE)		o ENUM - E.164 Number Mapping is described in Section 5.1.1.2
	The originating SSP would likely perform steps 1-4, and the target SSP would		o FQDN - Fully Qualified Domain Name
	likely perform steps 4-5.
	In the case the target SSP changes, then steps 1-4 would be repeated. This is		o TN DB - Telephone Number Database
	reflected in Figure 2 that shows the target SSP with its own peering functions.		o IP - IPv4/v6 Address
	3.1. Relationships between functions/elements		o RTP - Real-time Transport Protocol is defined in [RFC3550]
	- An SBE can contain a SF function.		+=============++ ++==============+
	- An SF can perform LUF and LRF functions.		|| ||
	- As an additional consideration, a Session Border Controller [SBC RFC], can		+-----------+ +-----------+
	contain an SF, SBE and DBE, and may perform the LUF and LRF functions.		| SBE | | SBE |
	- The following functions can communicate as follows, depending upon various		| +-----+ | SIP +-----+ | +-----+ |
	real-world implementations:		| | LUF |<-|------>|ENUM | | | LUF | |
	o SF can communicate with LUF, LRF, SBE and SF		| +-----+ | ENUM |TN DB| | +-----+ |
	o LUF can communicator with SF and SBE		SIP | | +-----+ | |
	o LRF can communicate with SF and SBE		------>| +-----+ | DNS +-----+ | +-----+ |
			| | LRF |<-|------>|FQDN | | | LRF | |
			| +-----+ | |IP | | +-----+ |
			| +-----+ | SIP +-----+ | +-----+ |
			| | SF |<-|----------------|->| SF | |
			| +-----+ | | +-----+ |
			+-----------+ +-----------+
			|| ||
			+-----------+ +-----------+
			RTP | DBE | RTP | DBE |
			------>| |--------------->| |
			+-----------+ +-----------+
			|| ||
			SSP1 Network || || SSP2 Network
			+=============++ ++=============+
	4. Recommended SSP Procedures		Figure 1
	This section describes the functions in more detail and provides some		For further details on the elements and functions described in this
	recommendations on the role they would play in a SIP call in a Layer 5 peering		figure, please refer to [RFC5486].
	scenario.
	Some of the information in the section is taken from [14] and is put here for		3. Procedures of Inter-domain SSP Session Establishment
	continuity purposes.
	4.1. Originating SSP Procedures		This document assumes that in order for a session to be established
			from a User Agent (UA) in the Originating SSP's network to a UA in
			the Target SSP's network the following steps are taken:
	4.1.1. The Look-Up Function (LUF)		1. Determine the target SSP via the LUF. (Note: If the target
			address represents a resource within the originating SSP, the
			behavior is out-of-scope with respect to this draft.)
	Purpose is to determine the SF of the target domain of a given request and		2. Determine the address of the SF of the target SSP via the LRF.
	optionally develop Session Establishment Data.
	4.1.1.1. Target Address Analysis		3. Establish the session
	When the originating SSP receives a request to communicate, it analyzes the		4. Exchange the media, which could include voice, video, text, etc.
	target URI to determine whether the call needs to be routed internal or
	external to its network. The analysis method is internal to the SSP; thus,
	outside the scope of SPEERMINT.
	If the target address does not represent a resource inside the originating		5. End the session
	SSP's administrative domain or federation of domains, then the originating SSP
	performs a Lookup Function (LUF) to determine a target address, and then is
	resolves 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 type, the		The originating SSP would likely perform steps 1-4, and the target
	originating SSP follows the procedures in [8]. If the highest priority		SSP would likely perform steps 4-5.
	supported URI scheme is sip: or sips: the originating SSP skips to 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 SSP skips to SIP DNS
	resolution in Section 4.1.2.1.
	If the target address corresponds to a specific E.164 address, the SSP may need		If the target SSP is also an indirect peer, then steps 1-4 may be
	to perform some form of number plan mapping according to local policy. For		repeated. This is reflected in Figure 1 that shows the target SSP
	example, in the United States, a dial string beginning "011 44" could be		with its own peering functions.
	converted to "+44", or in the United Kingdom "00 1" could be converted to "+1".
	Once the SSP has an E.164 address, it can use ENUM.
	4.1.1.2. ENUM Lookup		4. Relationships between functions/elements
	If an external E.164 address is the target, the originating SSP consults the		o An SBE can contain a SF function.
	public "User ENUM" rooted at e164.arpa, according to the procedures described
	in RFC 3761. The SSP must query for the "E2U+sip" enumservice as described in
	RFC 3764 [11], but MAY check for other enumservices. The originating SSP MAY
	consult a cache or alternate representation of the ENUM data rather than actual
	DNS queries. Also, the SSP may skip actual DNS queries if the originating SSP
	is sure that the target address country code is not represented in e164.arpa.
	If a sip: or sips: URI is chosen the SSP skips to Section 5.1.6.
	If an im: or pres: URI is chosen for based on an "E2U+im" [8] or "E2U+pres" [9]		o An SF can perform LUF and LRF functions.
	enumserver, the SSP follows the procedures for resolving these URIs to URIs for
	specific protocols such a SIP or XMPP as described in the previous section.
	4.1.2. Location Routing Function (LRF)		o As an additional consideration, in current Session Border
			Controller (SBC) implementations, an SBC can contain an SF, SBE
			and DBE, and may perform the LUF and LRF functions.
	The LRF of an Originating SSP analyzes target address and target domain		o The following functions can communicate as follows, depending upon
	identified by the LUF, and discovers the next hop signaling function (SF) in a		various real-world implementations:
	peering relationship. The resource to determine the SF of the target domain
	might be provided by a third-party as in the assisted-peering case. The
	following sections define mechanisms which may be used by the LRF. These are
	not in any particular order and, importantly, not all of them may be used.
	4.1.2.1. DNS Resolution		* SF can communicate with LUF, LRF and another SF
	The originating SSP uses the procedures in RFC 3263 [4] Section 4 to determine		* LUF can communicate with SF
	how to contact the receiving SSP. To summarize the RFC 3263 procedure: unless
	these are explicitly 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 or AAAA records.
	When communicating with another SSP, entities compliant to this document should		* LRF can communicate with SF
	select a TLS-protected transport for communication from the originating SSP to
	the receiving SSP if available.
	4.1.2.2. Routing Table		5. Recommended SSP Procedures
	If there are no End User ENUM records and the Originating SSP cannot discover		This section describes the functions in more detail and provides some
	the carrier-of-record or if the Originating SSP cannot reach the carrier-of-		recommendations on the role they would play in an example SIP
	record via SIP peering, the Originating SSP may deliver the call to the PSTN or		telephony call scenario.
	reject it. Note that the originating SSP may forward the call to another SSP
	for PSTN gateway termination by prior arrangement using the routing table.
	If so, the originating SSP rewrites the Request-URI to address the gateway		Some of the information in the section is taken from
	resource in the target SSP's domain and MAY forward the request on to that SSP		[I-D.ietf-speermint-requirements] and is put here for continuity
	using the procedures described in the remainder of these steps.		purposes.
	4.1.2.3. LRF to LRF Routing		5.1. Originating SSP Procedures
	Communications between the LRF of two interconnecting SSPs may use DNS or		5.1.1. The Look-Up Function (LUF)
	statically provisioned IP Addresses for reachability. Other inputs to
	determine the path may be code-based routing, method-based routing, Time of
	day, least cost and/or source-based routing.
	4.1.3. The Signaling Path Border Element (SBE)		Purpose is to determine the SF of the target domain of a given
			request and optionally develop Session Establishment Data.
	The purpose of signaling function is to perform routing of SIP messages as well		5.1.1.1. Target Address Analysis
	as optionally implement security and policies on SIP messages, and to assist in
	discovery/exchange of parameters to be used by the Media Function (MF).
	The signaling function performs the routing of SIP messages. The optional		When the originating SSP receives a SIP request, it analyzes the
	termination and re-initiation of calls may be performed by the signaling path		target URI to determine whether the call needs to be routed internal
	Session Border Element (SBE), or other signaling elements.		or external to its network.
	Optionally, a SF may perform additional functions such as Session Admission		If the target address does not represent a resource inside the
	Control, SIP Denial of Service protection, SIP Topology Hiding, SIP header		originating SSP's administrative domain, then the originating SSP
	normalization, SIP security, privacy, and encryption.		performs a Lookup (LUF) to determine the target domain, and then it
			resolves the call routing data by using Location Routing (LRF).
	The SF of a SBE can also process SDP payloads for media information such as		For example, if the request to communicate is for an im: or pres: URI
	media type, bandwidth, and type of codec; then, communicate this information to		type, the originating SSP follows the procedures in [RFC3861]. If
	the media function. Signaling function may optionally communicate with the		the highest priority supported URI scheme is sip: or sips: the
	network to pass Layer 3 related policies [10]		originating SSP skips to SIP DNS resolution. Likewise, if the target
			address is already a sip: or sips: URI in an external domain, the
			originating SSP skips to SIP DNS resolution in Section 5.1.2.1
	4.1.3.1. Establishing a Trusted Relationship		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
			local policy. For example, in the United States, a dial string
			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
			address, it can use ENUM.
	Depending on the security needs and trust relationships between SSPs, different		5.1.1.2. ENUM Lookup
	security mechanism can be used to establish SIP calls. These are discussed in
	the following subsections.
	4.1.3.1.1. IPSec		If an external E.164 address is the target, the originating SSP
			consults a private or public ENUM server, according to the procedures
			described in [RFC3761]. The SSP must query for the "E2U+sip"
			enumservice as described in [RFC3764], but MAY check for other
			enumservices. The originating SSP MAY consult a cache or alternate
			representation of the ENUM data rather than actual DNS queries.
			Also, the SSP may skip actual DNS queries if the target domain is
			represented as an IPv4/v6 address.
	In certain deployments the use of IPSec between the signaling functions of the		If an im: or pres: URI is chosen for based on an "E2U+im" [RFC3861]
	originating and terminating domains can be used as a security mechanism instead		or "E2U+pres" [RFC3953] enumserver, the SSP follows the procedures
	of TLS.		for resolving these URIs to URIs for specific protocols such a SIP or
			XMPP.
	4.1.3.1.2. Co-Location		5.1.2. Location Routing Function (LRF)
	In this scenario the SFs are co-located in a physically secure location and/or		The LRF of an Originating SSP analyzes the target address and target
	are members of a segregated network. In this case messages between the		domain identified by the LUF, and discovers the next hop signaling
	originating and terminating SSPs would be sent as clear text.		function (SF) in a peering relationship. The resource to determine
			the SF of the target domain might be provided by a third-party as in
			the indirect peering case. The following sections define mechanisms
			which may be used by the LRF. These are not in any particular order
			and, importantly, not all of them may be used.
	4.1.3.2. Sending the SIP request		5.1.2.1. DNS resolution
	Once a trust relationship between the peers is established, the originating SSP		The originating SSP uses the procedures in [RFC3263] to determine how
	sends the request.		to contact the target SSP. To summarize the RFC 3263 procedure:
			unless these are explicitly encoded in the target URI, a transport is
			chosen using Naming Authority Pointer (NAPTR) records, a port is
			chosen using SRV records, and an address is chosen using A or AAAA
			records.
	4.2. Target SSP Procedures		When communicating with another SSP, entities compliant to this
			document should select a TLS-protected transport for communication
			from the Originating SSP to the target SSP if available.
	4.2.1. The Ingress Signaling Path Border Element (SBE)		5.1.2.2. Routing Table
	4.2.1.1. TLS		If there are no End User ENUM records and the Originating SSP cannot
			discover the carrier-of-record or if the Originating SSP cannot reach
			the carrier-of-record via SIP peering, the Originating SSP may
			deliver the call to the PSTN or reject it. Note that the originating
			SSP may forward the call to another SSP for PSTN gateway termination
			by prior arrangement using the routing table.
	When the receiving SSP receives a TLS client hello, it responds with its		If so, the originating SSP rewrites the Request-URI to address the
	certificate. The Target SSP certificate should be valid and rooted in a well-		gateway resource in the target SSP's domain and MAY forward the
	known certificate authority. The procedures to authenticate the SSP's		request on to that SSP using the procedures described in the
	originating domain are specified in [24].		remainder of these steps.
	The SF of the Target SSP verifies that the Identity header is valid,		5.1.2.3. LRF to LRF Routing
	corresponds to the message, corresponds to the Identity-Info header, and that
	the domain in the From header corresponds to one of the domains in the TLS
	client certificate.
	4.2.1.2. Receive SIP requests		Communication between the LRF of two interconnecting SSPs may use DNS
			or statically provisioned IP Addresses for reachability. Other
			inputs to determine the path may be code-based routing, method-based
			routing, Time of day, least cost and/or source-based routing.
	Once a trust relationship is established, the Target SSP is prepared to receive		5.1.3. Signaling Path Border Element (SBE)
	incoming SIP requests. For new requests (dialog forming or not) the receiving
	SSP verifies if the target (request-URI) is a domain that for which it is
	responsible. For these requests, there should be no remaining Route header
	field values. For in-dialog requests, the receiving SSP can verify that it
	corresponds to the top-most Route header field value.
	The receiving SSP may reject incoming requests due to local policy. When a		The purpose of signaling path border element is to perform routing of
	request is rejected because the originating SSP is not authorized to peer, the		SIP messages as well as optionally implement security and policies on
	receiving SSP should respond with a 403 response with the reason phrase		SIP messages, and to assist in discovery/exchange of parameters to be
	"Unsupported Peer".		used by the Media Function (MF).
	4.3. Data Path Border Element (DBE)		The signaling function performs the routing of SIP messages. The
			optional termination and re-initiation of calls may be performed by
			the signaling path Session Border Element (SBE), or other signaling
			elements.
	The purpose of the DBE [RFC 5486] is to perform media related functions such as		Optionally, the SF of a SBE may perform additional functions such as
	media transcoding and media security implementation between two SSPs.		Session Admission Control, SIP Denial of Service protection, SIP
			Topology Hiding, SIP header normalization, SIP security, privacy, and
			encryption.
	An Example of this is to transform a voice payload from one codec (e.g., G.711)		The SF of a SBE can also process SDP payloads for media information
	to another (e.g., EvRC). Additionally, the MF may perform media relaying,		such as media type, bandwidth, and type of codec; then, communicate
	media security, privacy, and encryption.		this information to the media function. Signaling function may
			optionally communicate with the network to pass Layer 3 related
			policies.
	5. Address space considerations		5.1.4. Establishing a Trusted Relationship
	Peering must occur in a common IP address space, which is defined by the		Depending on the security needs and trust relationships between SSPs,
	federation, which may be entirely on the public Internet, or some private		different security mechanism can be used to establish SIP calls.
	address space. The origination or termination networks may or may not entirely		These are discussed in the following subsections.
	be in the same address space. If they are not, then a network address
	translation (NAT) or similar may be needed before the signaling or media is
	presented correctly to the federation. The only requirement is that all
	associated entities across the peering interface are reachable.
	6. Security Considerations		5.1.4.1. IPSec
	In all cases, cryptographic-based security should be maintained as an optional		In certain deployments the use of IPSec between the signaling
	requirement between peering providers conditioned on the presence or absence of		functions of the originating and terminating domains can be used as a
	underlying physical security of SSP connections, e.g. within the same secure		security mechanism instead of TLS.
	physical building.
	In order to maintain a consistent approach, unique and specialized security		5.1.4.2. Co-Location
	requirements common for the majority of peering relationships, should be
	standardized within the IETF. These standardized methods may enable
	capabilities such as dynamic peering relationships across publicly maintained
	interconnections.
	7. IANA Considerations		In this scenario the SFs are co-located in a physically secure
			location and/or are members of a segregated network. In this case
			messages between the originating and terminating SSPs would be sent
			as clear text.
	There are no IANA considerations at this time.		5.1.4.3. Sending the SIP Request
	8. Acknowledgments		Once a trust relationship between the peers is established, the
			originating SSP sends the request.
	The working group thanks Sohel Khan for his initial architecture		5.2. Target SSP Procedures
	draft that helped to initiate work on this draft.		5.2.1. The Ingress SBE
	A significant portion of this draft is taken from [14] with		5.2.1.1. TLS
	permission from the author R. Mahy. The other important contributor
	is Otmar Lendl. Special thanks to Jim McEachern for detailed comments and
	feedback.
	9. References		When the target SSP receives a TLS client hello, it responds with its
			certificate. The Originating SSP certificate should be valid and
			rooted in a well-known certificate authority. The procedures to
			authenticate the SSP's originating domain are specified in
			[I-D.ietf-sip-domain-certs].
	9.1. Normative References		The SF of the Target SSP verifies that the Identity header is valid,
			corresponds to the message, corresponds to the Identity-Info header,
			and that the domain in the From header corresponds to one of the
			domains in the TLS client certificate.
	[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels",		5.2.1.2. Receive SIP Requests
	BCP 14, RFC 2119, March 1997.
	[2] Mealling, M. and R. Daniel, "The Naming Authority Pointer (NAPTR) DNS		Once a trust relationship is established, the Target SSP is prepared
	Resource Record", RFC 2915, September 2000.		to receive incoming SIP requests. For new requests (dialog forming
			or not) the receiving SSP verifies if the target (request-URI) is a
			domain for which it is responsible. For these requests, there should
			be no remaining Route header field values. For in-dialog requests,
			the receiving SSP can verify that it corresponds to the top-most
			Route header field value.
	[3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson,		The receiving SSP may reject incoming requests due to local policy.
	J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation		When a request is rejected because the originating SSP is not
	Protocol", RFC 3261, June 2002.		authorized to peer, the receiving SSP should respond with a 403
			response with the reason phrase "Unsupported Peer".
	[4] Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol (SIP):		5.3. Data Path Border Element (DBE)
	Locating SIP Servers", RFC 3263, June 2002.
	[5] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., and T.		The purpose of the DBE [RFC5486] is to perform media related
	Wright, "Transport Layer Security (TLS) Extensions", RFC 4366, April		functions such as media transcoding and media security implementation
	2006.		between two SSPs.
	[6] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A		An Example of this is to transform a voice payload from one codec
	Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July		(e.g., G.711) to another (e.g., Enhanced Variable Rate Codec (EvRC)).
	2003.		Additionally, the MF may perform media relaying, media security,
			privacy, and encryption.
	[7] Peterson, J., Liu, H., Yu, J., and B. Campbell, "Using E.164 numbers		6. Acknowledgments
	with the Session Initiation Protocol (SIP)", RFC 3824, June 2004.
	[8] Peterson, J., "Address Resolution for Instant Messaging and		The working group thanks Sohel Khan for his initial architecture
	Presence",RFC 3861, August 2004.		draft that helped to initiate work on this draft.
	[9] Peterson, J., "Telephone Number Mapping (ENUM) Service Registration for		Other contributors include Rohan Mahy, Otmar Lendl, Jim McEachern and
	Presence Services", RFC 3953, January 2005.		John Elwell for detailed comments and feedback.
	[10] ETSI TS 102 333: " Telecommunications and Internet converged Services		7. IANA Considerations
	and Protocols for Advanced Networking (TISPAN); Gate control protocol".
	[11] Peterson, J., "enumservice registration for Session Initiation Protocol		This memo includes no request to IANA.
	(SIP) Addresses-of-Record", RFC 3764, April 2004.
	[12] Livingood, J. and R. Shockey, "IANA Registration for an		8. Security Considerations
	Enumservice Containing PSTN Signaling Information", RFC 4769, November
	2006.
	9.2. Informative References		In all cases, cryptographic-based security should be maintained as an
			optional requirement between peering providers conditioned on the
			presence or absence of underlying physical security of SSP
			connections, e.g. within the same secure physical building.
	[13] Malas, D., "SPEERMINT Terminology", draft-ietf-speermint-terminology-16		In order to maintain a consistent approach, unique and specialized
	(work in progress), February 2008.		security requirements common for the majority of peering
			relationships, should be standardized within the IETF. These
			standardized methods may enable capabilities such as dynamic peering
			relationships across publicly maintained interconnections.
	[14] Mule, J-F., "SPEERMINT Requirements for SIP-based VoIP Interconnection",		9. Normative References
	draft-ietf-speermint-requirements-04.txt, February 2008.
	[15] Mahy, R., "A Minimalist Approach to Direct Peering", draft-		[I-D.ietf-sip-domain-certs]
	mahy-speermint-direct-peering-02.txt, July 2007.		Gurbani, V., Lawrence, S., and B. Laboratories, "Domain
			Certificates in the Session Initiation Protocol (SIP)",
			draft-ietf-sip-domain-certs-05 (work in progress),
			March 2010.
	[16] Penno, R., et al., "SPEERMINT Routing Architecture Message		[I-D.ietf-speermint-requirements]
	Flows", draft-ietf-speermint-flows-02.txt", April 2007.		Mule, J., "SPEERMINT Requirements for SIP-based Session
			Peering", draft-ietf-speermint-requirements-09 (work in
			progress), October 2009.
	[17] Houri, A., et al., "RTC Provisioning Requirements", draft-		[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
	houri-speermint-rtc-provisioning-reqs-00.txt, June, 2006.		A., Peterson, J., Sparks, R., Handley, M., and E.
			Schooler, "SIP: Session Initiation Protocol", RFC 3261,
			June 2002.
	[18] Habler, M., et al., "A Federation based VOIP Peering		[RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation
	Architecture", draft-lendl-speermint-federations-03.txt, September 2006.		Protocol (SIP): Locating SIP Servers", RFC 3263,
			June 2002.
	[19] Mahy, R., "A Telephone Number Mapping (ENUM) Service		[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
	Registration for Instant Messaging (IM) Services", draft-ietf-		Jacobson, "RTP: A Transport Protocol for Real-Time
	enum-im-service-03 (work in progress), March 2006.		Applications", STD 64, RFC 3550, July 2003.
	[20] Haberler, M. and R. Stastny, "Combined User and Carrier ENUM in the		[RFC3761] Faltstrom, P. and M. Mealling, "The E.164 to Uniform
	e164.arpa tree", draft-haberler-carrier-enum-03 (work in progress),		Resource Identifiers (URI) Dynamic Delegation Discovery
	March 2006.		System (DDDS) Application (ENUM)", RFC 3761, April 2004.
	[21] Penno, R., Malas D., and Melampy, P., "A Session Initiation		[RFC3764] Peterson, J., "enumservice registration for Session
	Protocol (SIP) Event package for Peering", draft-penno-sipping-peering-		Initiation Protocol (SIP) Addresses-of-Record", RFC 3764,
	package-00 (work in progress), September 2006.		April 2004.
	[22] Hollander, D., Bray, T., and A. Layman, "Namespaces in XML", W3C REC		[RFC3861] Peterson, J., "Address Resolution for Instant Messaging
	REC-xml-names-19990114, January 1999.		and Presence", RFC 3861, August 2004.
	[23] Burger, E (Ed.), "A Mechanism for Content Indirection in		[RFC3953] Peterson, J., "Telephone Number Mapping (ENUM) Service
	Session Initiation Protocol (SIP) Messages", RFC 4483, May 2006		Registration for Presence Services", RFC 3953,
			January 2005.
	[24] Gurbani, V., Lawrence, S., and B. Laboratories, "Domain Certificates in		[RFC5486] Malas, D. and D. Meyer, "Session Peering for Multimedia
	the Session Initiation Protocol (SIP)", draft-ietf-sip-domain-certs-00		Interconnect (SPEERMINT) Terminology", RFC 5486,
	(work in progress), November 2007.		March 2009.
	Author's Addresses		Authors' Addresses
	Adam Uzelac		Adam Uzelac (editor)
	Global Crossing		Global Crossing
	Rochester, NY - USA		Rochester, NY
			US
	Email: adam.uzelac@globalcrossing.com		Email: adam.uzelac@globalcrossing.com
	Reinaldo Penno		Reinadlo Penno
	Juniper Networks		Juniper Networks
	Sunnyvale, CA - USA		Sunnyvale, CA
			US
	Email: rpenno@juniper.net		Email: rpenno@juniper.net
	Mike Hammer		Mike Hammer
	Cisco Systems		Cisco Systems
	Herndon, VA - USA		Herndon, VA
	Email: mhammer@cisco.com		US
	Sohel Khan, Ph.D.
	Comcast Cable Communications
	USA
	Email: sohel_khan@cable.comcast.com
			Email: mhammer@cisco.com
	Daryl Malas		Daryl Malas
	CableLabs		CableLabs
	Louisville, CO - USA		Louisville, CO
			US
	Email: d.malas@cablelabs.com		Email: d.malas@cablelabs.com
			Sohel Khan
			Comcast
			Philadelphia, PA
			US
			Email: sohel_khan@cable.comcast.com
	Hadriel Kaplan		Hadriel Kaplan
	Acme Packet		Acme Packet
			Burlington, MA
			US
	Email: hkaplan@acmepacket.com		Email: hkaplan@acmepacket.com
	Jason Livingood		Jason Livingood
	Comcast		Comcast
	Email: Jason_livingood@cable.comcast.com		Philadelphia, PA
			US
			Email: Jason_Livingood@cable.comcast.com
	David Schwartz		David Schwartz
	Kayote Systems		XConnect Global Networks
	Email: david.schwartz@kayote.com		Jerusalem
			Israel
			Email: dschwartz@xconnnect.net
			Richard Shockey
			Shockey Consulting
			US
	Rich Shockey
	Unaffiliated
	Email: Richard@shockey.us		Email: Richard@shockey.us
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