draft-ietf-speermint-architecture-08.txt		draft-ietf-speermint-architecture-09.txt
	Speermint Working Group A.Uzelac(Ed.)		Speermint Working Group A.Uzelac(Ed.)
	Internet Draft Global Crossing		Internet Draft Global Crossing
	Intended status: Informational		Intended status: Informational
	Expires: September 2009		Expires: May 2010
	March 2, 2009		November 10, 2009
	SPEERMINT Peering Architecture		SPEERMINT Peering Architecture
	draft-ietf-speermint-architecture-08		draft-ietf-speermint-architecture-09
	Status of this Memo		Status of this Memo
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	Copyright Notice		Copyright Notice
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	Abstract		Abstract
	This document defines the SPEERMINT peering architecture, its functional		This document defines the SPEERMINT peering architecture, its functional
	components and peering interface functions. It also describes the steps taken		components and peering interface functions. It also describes the steps taken
	to establish a session between two peering domains in the context of the		to establish a session between two peering domains in the context of the
	functions defined.		functions defined.
	Table of Contents		Table of Contents
	1. Introduction...................................................3		1. Introduction...................................................2
	2. Network Context................................................3		2. Reference SPEERMINT Architecture...............................4
	3. Reference SPEERMINT Architecture...............................4		3. Procedures of Inter-domain SSP Session Establishment...........4
	4. Procedures of Interdomain SSP Session Establishment............6		3.1. Relationships between functions/elements..................5
	5. Recommended SSP Procedures.....................................7		4. Recommended SSP Procedures.....................................5
	5.1. Originating SSP Procedures................................7		4.1. Originating SSP Procedures................................5
	5.1.1. The Look-Up Function (LUF)...........................7		4.1.1. The Look-Up Function (LUF)...........................5
	5.1.1.1. Target address analysis.........................7		4.1.1.1. Target Address Analysis.........................6
	5.1.1.2. End User ENUM Lookup............................8		4.1.1.2. ENUM Lookup.....................................6
	5.1.1.3. Infrastructure ENUM lookup......................8		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. SIP DNS Resolution..............................8		4.1.2.2. Routing Table...................................7
	5.1.2.2. Routing Table...................................9		4.1.2.3. LRF to LRF Routing..............................7
	5.1.2.3. SIP Redirect Server.............................9		4.1.3. The Signaling Path Border Element (SBE)..............7
	5.1.3. The Signaling Function (SF)..........................9		4.1.3.1. Establishing a Trusted Relationship.............8
	5.1.3.1. Establishing a Trusted Relationship.............9		4.1.3.2. Sending the SIP request.........................8
	5.1.3.2. Sending the SIP request........................10		4.2. Target SSP Procedures.....................................8
	5.2. Terminating SSP Procedures...............................10		4.2.1. The Ingress Signaling Path Border Element (SBE)......8
	5.2.1. The Location Function (LF)..........................10		4.2.1.1. TLS.............................................8
	5.2.1.1. Publish ENUM records...........................10		4.2.1.2. Receive SIP requests............................9
	5.2.1.2. Publish SIP DNS records........................11		4.3. Data Path Border Element (DBE)............................9
	5.2.1.3. Subscribe Notify...............................11		5. Address space considerations...................................9
	5.2.2. Signaling Function (SF).............................11		6. Security Considerations........................................9
	5.2.2.1. TLS............................................11		7. IANA Considerations...........................................10
	5.2.2.2. Receive SIP requests...........................11		8. Acknowledgments...............................................10
	5.3. Target SSP Procedures....................................12		9. References....................................................11
	5.3.1. Signaling Function (SF).............................12		9.1. Normative References.....................................11
	5.3.1.1. TLS............................................12		9.2. Informative References...................................12
	5.3.1.2. Receive SIP requests...........................12		Author's Addresses...............................................13
	5.4. Media Function (MF)......................................12
	5.5. Policy Considerations....................................12
	6. Call Control and Media Control Deployment Options.............13
	7. Address space considerations..................................14
	8. Security Considerations.......................................15
	9. IANA Considerations...........................................15
	10. Acknowledgments..............................................15
	11. References...................................................16
	11.1. Normative References....................................16
	11.2. Informative References..................................17
	Author's Addresses...............................................18
	1. Introduction		1. Introduction
	The objective of this document is to define a reference peering architecture in		The objective of this document is to define a reference peering architecture in
	the context of Session PEERing for Multimedia INTerconnect (SPEERMINT). In this		the context of Session PEERing for Multimedia INTerconnect (SPEERMINT). In this
	process, we define the peering reference architecture, its functional		process, we define the peering reference architecture, its functional
	components, and peering interface functions from the perspective of a SIP		components, and peering interface functions from the perspective of a SIP
	Service provider's (SSP) network.		Service provider's (SSP) network.
	This architecture allows the interconnection of two SSPs in layer 5 peering as		This architecture allows the interconnection of two SSPs in layer 5 peering as
	skipping to change at page 3, line 27		skipping to change at page 4, line 5
	this document do not show routers so that the focus is on Layer 5 protocol		this document do not show routers so that the focus is on Layer 5 protocol
	aspects.		aspects.
	This document uses terminology defined in the SPEERMINT Terminology document		This document uses terminology defined in the SPEERMINT Terminology document
	[13], so the reader should be familiar with all the terms defined there.		[13], so the reader should be familiar with all the terms defined there.
	In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL",		In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
	"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are		"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are
	to be interpreted as described in [RFC2119].		to be interpreted as described in [RFC2119].
	2. Network Context		2. Reference SPEERMINT Architecture
	Figure 1 allows for the following potential SPEERMINT peering scenarios:
	o Enterprise to Enterprise across the public Internet
	o Enterprise to SSP across the public Internet
	o SSP to SSP across the public Internet
	o Enterprise to enterprise across a private Layer 3 network
	o Enterprise to SSP across a private Layer 3 network
	o SSP to SSP across a private Layer 3 network
	+-------------------+
	| |
	| Public |
	| SIP |
	| Peering |
	| |
	+-------------------+
	|
	-----
	+-----------+ / \ +-----------+
	|Enterprise | -- -- |Enterprise |
	|Provider A |-----------/ \-----------|Provider B |
	+-----------+ -- -- +-----------+
	/ Public \
	| Internet |
	\ (Layer 3) /
	+-----------+ -- -- +-----------+
	| SSP C |-----------\ /-----------| SSP D |
	| | -- -- | |
	+-----------+ \_____/ +-----------+
	| Layer 3 Peering
	| Point (out of scope)
	-----
	+-----------+ / \ +-----------+
	|Enterprise | -- -- |Enterprise |
	|Provider E |-----------/ \-----------|Provider F |
	+-----------+ -- Private -- +-----------+
	/ Network \
	| (Layer 3) |
	\ /
	+-----------+ -- -- +-----------+
	| SSP G |-----------\ /-----------| SSP H |
	| | -- -- | |
	+-----------+ \____/ +-----------+
	|
	+-------------------+
	| Private |
	| SIP |
	| Peering |
	| |
	+-------------------+
	Figure 1: SPEERMINT Network Context
	3. Reference SPEERMINT Architecture
	Figure 2 depicts the SPEERMINT architecture and logical functions that form the		Figure 2 depicts the SPEERMINT architecture and logical functions that form the
	peering between two SSPs.		peering between two SSPs.
	+------+		--------------- ---------------
	| DNS, |		/ \ / \
	+---------->| Db, |<---------+		| +--LUF-+ | +------+ | +--LUF-+ |
	| | etc | |		| |->| | | | ENUM | | | |<-| |
	| +------+ |		| | | +------------>| TN DB|<------------+ | | |
	| |		| | | | | +------+ | | | | |
	------|-------- -------|-------		| | +------+ | | +------+ | |
	/ v \ / v \		| | | | | |
	| +--LUF-+ | | +--LUF-+ |		| | +--LRF-+ | +--------+ | +--LRF-+ | |
	| | | | | | | |		| |->| | | | DNS | | | |<-| |
	| | | | | | | |		| | | +----------->|IP Addrs|<-----------+ | | |
	| | | | | | | |		| | | | | +--------+ | | | | |
	| +------+ | | +------+ |		| | +------+ | | +------+ | |
	| | | |		| | | | | |
	| +--LRF-+ | | +--LRF-+ |		| | | | | |
	| | | | | | | |		| | +-------+ +-------+ | |
	| | | | | | | |		| ----------->| | | |<----------- |
	| | | | | | | |		| | SBE |<------------>| SBE | |
	| +------+ | | +------+ |		| | | | | |
	| | | |		| +-------+ +-------+ |
	| | | |		| SSP1 | | SSP2 |
	| +---SF--+ +---SF--+ |		| +-------+ +-------+ |
	| | | | | |		| | | | | |
	| | SBE | | SBE | |		| | DBE |<------------>| DBE | |
	| Originating | | | | Target |		| | | | | |
	| +---SF--+ +---SF--+ |		| +-------+ +-------+ |
	| SSP | | SSP |		\ / \ /
	| +---MF--+ +---MF--+ |		--------------- ---------------
	| | | | | |		Figure 1: Reference SPEERMINT Architecture
	| | DBE | | DBE | |
	| | | | | |
	| +---MF--+ +---MF--+ |
	\ / \ /
	--------------- ---------------
	Figure 2: Reference SPEERMINT Architecture
	The following procedures are implemented by a set of peering functions:
	The Look-Up Function (LUF) provides a mechanism for determining for a given
	request the target domain to which the request should be routed.
	The Location Routing Function (LRF) determines for the target domain of a given
	request the location of the SF in that domain and optionally develops other
	Session Establishment Data (SED) required to route the request to that domain.
	The Signaling Function (SF) provides SIP call routing, to optionally perform
	termination and re-initiation of call, to 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 Media Function (MF) provides media related functions such as media
	transcoding, topology hiding and media security implementation between two
	SSPs.
	The intention of defining these functions is to provide a framework for design		For further details on the elements and functions described in this figure,
	segmentation and allow each one to evolve independently.		please refer to [RFC 5486].
	4. Procedures of Interdomain SSP Session Establishment		3. Procedures of Inter-domain SSP Session Establishment
	This document assumes that in order for a session to be established from a UA		This document assumes that in order for a session to be established from a UA
	in the originating SSP's network to an UA in the Target SSP's network the		in the Originating SSP's network to an UA in the Target SSP's network the
	following steps are taken:		following steps are taken:
	1. analyze the target address.		1. Determine the target SSP via the LUF.
	a. If the target address represents an intra-SSP resource, the		a. If the target address represents an intra-SSP resource, the
	behavior is out-of-scope with respect to this draft.		behavior is out-of-scope with respect to this draft.
	2. determine the target SSP (LUF)		2. Determine the address of the SF of the target SSP via the LRF.
	3. determine the SF next-hop in the target SSP (LRF)
	4. enforce authentication and potentially other policies
	5. determine of the UA
	6. establish the session,		3. Establish the session
	7. transfer of media which could include voice, video, text and others,		4. Exchange the media, which could include voice, video, tec, etc.
	8. terminate the session (BYE)		5. End the session (BYE)
	The originating SSP would likely perform steps 1-4, and the target SSP would		The originating SSP would likely perform steps 1-4, and the target SSP would
	likely perform steps 4-5.		likely perform steps 4-5.
	In the case the target SSP changes, then steps 1-4 would be repeated. This is		In the case the target SSP changes, then steps 1-4 would be repeated. This is
	reflected in Figure 2 that shows the target SSP with its own peering functions.		reflected in Figure 2 that shows the target SSP with its own peering functions.
	5. Recommended SSP Procedures		3.1. Relationships between functions/elements
			- 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.
			- The following functions can communicate as follows, depending upon various
			real-world implementations:
			o SF can communicate with LUF, LRF, SBE and SF
			o LUF can communicator with SF and SBE
			o LRF can communicate with SF and SBE
			4. 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 5 peering		recommendations on the role they would play in a SIP call in a Layer 5 peering
	scenario.		scenario.
	Some of the information in the section is taken from [14] and is put here for		Some of the information in the section is taken from [14] and is put here for
	continuity purposes.		continuity purposes.
	5.1. Originating SSP Procedures		4.1. Originating SSP Procedures
	5.1.1. The Look-Up Function (LUF)		4.1.1. The Look-Up Function (LUF)
	Purpose is to determine the SF of the target domain of a given request and		Purpose is to determine the SF of the target domain of a given request and
	optionally develop Session Establishment Data.		optionally develop Session Establishment Data.
	5.1.1.1. Target address analysis		4.1.1.1. Target Address Analysis
	When the originating SSP receives a request to communicate, it analyzes the		When the originating SSP receives a request to communicate, it analyzes the
	target URI to determine whether the call needs to be routed internal or		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,		external to its network. The analysis method is internal to the SSP; thus,
	outside the scope of SPEERMINT. Note that the SSP may also consult any manner		outside the scope of SPEERMINT.
	of private data sources to make this determination.
	If the target address does not represent a resource inside the originating		If the target address does not represent a resource inside the originating
	SSP's administrative domain or federation of domains, the originating SSP		SSP's administrative domain or federation of domains, then the originating SSP
	resolves the call routing data by using the Location Routing Function (LRF).		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		For example, if the request to communicate is for an im: or pres: URI type, the
	originating SSP follows the procedures in [8]. If the highest priority		originating SSP follows the procedures in [8]. If the highest priority
	supported URI scheme is sip: or sips: the originating SSP skips to SIP DNS		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:		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		or sips: URI in an external domain, the originating SSP skips to SIP DNS
	resolution in Section 5.1.2.1.		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 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		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		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".		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.		Once the SSP has an E.164 address, it can use ENUM.
	5.1.1.2. End User ENUM Lookup		4.1.1.2. ENUM Lookup
	If an external E.164 address is the target, the originating SSP consults the		If an external E.164 address is the target, the originating SSP consults the
	public "User ENUM" rooted at e164.arpa, according to the procedures described		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		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		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		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		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.		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 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]		If an im: or pres: URI is chosen for based on an "E2U+im" [8] or "E2U+pres" [9]
	enumserver, the SSP follows the procedures for resolving these URIs to URIs for		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.		specific protocols such a SIP or XMPP as described in the previous section.
	5.1.1.3. Infrastructure ENUM lookup		4.1.2. Location Routing Function (LRF)
	An originating SSP may check for a carrier-of-record in an Infrastructure ENUM
	domain according to the procedures described in [12]. As in the previous step,
	the SSP may consult a cache or alternate representation of the ENUM data in
	lieu of actual DNS queries. The SSP first checks for records for the "E2U+sip"
	enumservice, then for the "E2U+pstn" enumservice as defined in [21]. If a
	terminal record is found with a sip: or sips: URI, the SSP skips to Section
	5.1.2.1. , otherwise the SSP continues processing according to the next
	section.
	5.1.2. Location Routing Function (LRF)
	The LRF of an Originating SSP analyzes target address and target domain		The LRF of an Originating SSP analyzes target address and target domain
	identified by the LUF, and discovers the next hop signaling function (SF) in a		identified by the LUF, and discovers the next hop signaling function (SF) in a
	peering relationship. The resource to determine the SF of the target domain		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.		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.
	5.1.2.1. SIP DNS Resolution		4.1.2.1. DNS Resolution
	Once a sip: or sips: in an external domain is identified as the target, the		The originating SSP uses the procedures in RFC 3263 [4] Section 4 to determine
	originating SSP may apply local policy to decide whether forwarding requests to		how to contact the receiving SSP. To summarize the RFC 3263 procedure: unless
	the target domain is acceptable. The originating SSP uses the procedures in		these are explicitly encoded in the target URI, a transport is chosen using
	RFC 3263 [4] Section 4 to determine how to contact the receiving SSP. To		NAPTR records, a port is chosen using SRV records, and an address is chosen
	summarize the RFC 3263 procedure: unless these are explicitly encoded in the		using A or AAAA records.
	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. Note that these
	are queries of records in the global DNS.
	When communicating with another SSP, entities compliant to this document should		When communicating with another SSP, entities compliant to this document should
	select a TLS-protected transport for communication from the originating SSP to		select a TLS-protected transport for communication from the originating SSP to
	the receiving SSP if available.		the receiving SSP if available.
	5.1.2.2. Routing Table		4.1.2.2. Routing Table
	If there are no End User ENUM records and the Originating SSP cannot discover		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-		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		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		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.		for PSTN gateway termination by prior arrangement using the routing table.
	If so, the originating SSP rewrites the Request-URI to address the gateway		If so, the originating SSP rewrites the Request-URI to address the gateway
	resource in the target SSP's domain and MAY forward the request on to that SSP		resource in the target SSP's domain and MAY forward the request on to that SSP
	using the procedures described in the remainder of these steps.		using the procedures described in the remainder of these steps.
	5.1.2.3. SIP Redirect Server		4.1.2.3. LRF to LRF Routing
	A SIP Redirect Server using 3XX SIP Redirect is another option in resolving the		Communications between the LRF of two interconnecting SSPs may use DNS or
	next-hop SF of the target domain.		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.
	5.1.3. The Signaling Function (SF)		4.1.3. The Signaling Path Border Element (SBE)
	The purpose of signaling function is to perform routing of SIP messages as well		The purpose of signaling function is to perform routing of SIP messages as well
	as optionally implement security and policies on SIP messages, and to assist in		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).		discovery/exchange of parameters to be used by the Media Function (MF).
	The signaling function performs the routing of SIP messages. The optional		The signaling function performs the routing of SIP messages. The optional
	termination and re-initiation of calls may be performed by the signaling path		termination and re-initiation of calls may be performed by the signaling path
	Session Border Element (SBE).		Session Border Element (SBE), or other signaling elements.
	Optionally, a SF may perform additional functions such as Session Admission		Optionally, a SF may perform additional functions such as Session Admission
	Control, SIP Denial of Service protection, SIP Topology Hiding, SIP header		Control, SIP Denial of Service protection, SIP Topology Hiding, SIP header
	normalization, and SIP security, privacy and encryption.		normalization, SIP security, privacy, and encryption.
	The SF of a SBE can also process SDP payloads for media information such as		The SF of a SBE can also process SDP payloads for media information such as
	media type, bandwidth, and type of codec; then, communicate this information to		media type, bandwidth, and type of codec; then, communicate this information to
	the media function. Signaling function may optionally communicate with the		the media function. Signaling function may optionally communicate with the
	network to pass Layer 3 related policies [10]		network to pass Layer 3 related policies [10]
	5.1.3.1. Establishing a Trusted Relationship		4.1.3.1. Establishing a Trusted Relationship
	Depending on the security needs and trust relationships between SSPs, different		Depending on the security needs and trust relationships between SSPs, different
	security mechanism can be used to establish SIP calls. These are discussed in		security mechanism can be used to establish SIP calls. These are discussed in
	the following subsections.		the following subsections.
	5.1.3.1.1. TLS connection		4.1.3.1.1. IPSec
	Once a transport, port, and address are found, the originating SSP will open or
	find a reusable TLS connection to the peer. The procedures to authenticate the
	SSP's target domain is specified in [24]
	5.1.3.1.2. TLS
	If the trust relationship was established through TLS, the originating SSP can
	optionally verify and assert the senders identity using the SIP Identity
	mechanism.
	In addition, new requests should contain a valid Identity and Identity-Info
	header as described in [12]. The Identity-Info header must present a domain
	name that is represented in the certificate provided when establishing the TLS
	connection over which the request is sent. The originating SSP should include
	an Identity header on in-dialog requests as well if the From header field value
	matches an identity the originating SSP is willing to assert.
	5.1.3.1.3. IPSec
	In certain deployments the use of IPSec between the signaling functions of the		In certain deployments the use of IPSec between the signaling functions of the
	originating and terminating domains can be used as a security mechanism instead		originating and terminating domains can be used as a security mechanism instead
	of TLS.		of TLS.
	5.1.3.1.4. Co-Location		4.1.3.1.2. Co-Location
	In this scenario the SFs are co-located in a physically secure location and/or		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		are members of a segregated network. In this case messages between the
	originating and terminating SSPs would be sent as clear text.		originating and terminating SSPs would be sent as clear text.
	5.1.3.2. Sending the SIP request		4.1.3.2. Sending the SIP request
	Once a trust relationship between the peers is established, the originating SSP		Once a trust relationship between the peers is established, the originating SSP
	sends the request.		sends the request.
	5.2. Terminating SSP Procedures		4.2. Target SSP Procedures
	5.2.1. The Location Function (LF)
	5.2.1.1. Publish ENUM records
	The receiving SSP should participate by publishing "E2U+sip" and "E2U+pstn"
	records with sip: or sips: URIs wherever a public Infrastructure ENUM root is
	available. This assumes that the receiving SSP wants to peer by default. When
	the receiving SSP does not want to accept traffic from specific originating
	SSPs, it may still reject requests on a call-by-call basis.
	5.2.1.2. Publish SIP DNS records
	To receive SSP requests, the receiving SSP must insure that it publishes
	appropriate NAPTR, SRV, and address (A and/or AAAA) records in the LF relevant
	to the SSP's SF.
	5.2.1.3. Subscribe Notify
	Policies function may also be optionally implemented by dynamic subscribe,
	notify, and exchange of policy information and feature information among SSPs
	[21].
	5.2.2. Signaling Function (SF)		4.2.1. The Ingress Signaling Path Border Element (SBE)
	5.2.2.1. TLS		4.2.1.1. TLS
	When the receiving SSP receives a TLS client hello, it responds with its		When the receiving SSP receives a TLS client hello, it responds with its
	certificate. The Target SSP certificate should be valid and rooted in a well-		certificate. The Target SSP certificate should be valid and rooted in a well-
	known certificate authority. The procedures to authenticate the SSP's		known certificate authority. The procedures to authenticate the SSP's
	originating domain are specified in [24].		originating domain are specified in [24].
	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, and that		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		the domain in the From header corresponds to one of the domains in the TLS
	client certificate.		client certificate.
	5.2.2.2. Receive SIP requests		4.2.1.2. Receive SIP requests
	Once a trust relationship is established, the Target SSP is prepared to receive		Once a trust relationship is established, the Target SSP is prepared to receive
	incoming SIP requests. For new requests (dialog forming or not) the receiving		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		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		responsible. For these requests, there should be no remaining Route header
	field values. For in-dialog requests, the receiving SSP can verify that it		field values. For in-dialog requests, the receiving SSP can verify that it
	corresponds to the top-most Route header field value.		corresponds to the top-most Route header field value.
	The receiving SSP may reject incoming requests due to local policy. When a		The receiving SSP may reject incoming requests due to local policy. When a
	request is rejected because the originating SSP is not authorized to peer, the		request is rejected because the originating SSP is not authorized to peer, the
	receiving SSP should respond with a 403 response with the reason phrase		receiving SSP should respond with a 403 response with the reason phrase
	"Unsupported Peer".		"Unsupported Peer".
	5.3. Target SSP Procedures		4.3. Data Path Border Element (DBE)
	5.3.1. Signaling Function (SF)
	5.3.1.1. TLS
	When the receiving SSP receives a TLS client hello, it responds with its
	certificate. The Target SSP's certificate should be valid and rooted in a
	well-known certificate authority. The procedures to authenticate the SSP's
	originating domain are specified in [24].
	If the requests should contain a valid Identity and Identity-Info header as
	described in [24] the target SF 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.
	5.3.1.2. Receive SIP requests
	The procedures of the SF of the target SSP are the same as the ones described
	in section 5.2.2.2 with the addition that it might establish a connection to
	another target SSP, and in this case use the procedures recommended to an
	originating SS (section 5.1).
	5.4. Media Function (MF)
	The purpose of the MF is to perform media related functions such as media		The purpose of the DBE [RFC 5486] is to perform media related functions such as
	transcoding and media security implementation between two SSPs.		media transcoding and media security implementation between two SSPs.
	An Example of this is to transform a voice payload from one codec (e.g., G.711)		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 perform media relaying,		to another (e.g., EvRC). Additionally, the MF may perform media relaying,
	media security, privacy, and encryption.		media security, privacy, and encryption.
	5.5. Policy Considerations		5. Address space considerations
	In the context of the SPEERMINT working group when two SSPs peer, there MAY be
	a desire to exchange peering policy information dynamically. There are
	specifications in progress in the SIPPING working group to define policy
	exchange between an UA and a domain [23] and providing profile data to SIP user
	agents [24] These considerations borrow from both.
	Following the terminology introduced in [12], this package uses the terms
	Peering Session-Independent and Session-Specific policies in the following
	context.
	o Peering Session-Independent policies include Diffserv Marking, Policing,
	Session Admission Control, and domain reachabilities, amongst others. The
	time period between Peering Session-Independent policy changes is much
	greater than the time it takes to establish a call.
	o Peering Session-Specific polices includes supported connection/call rate,
	total number of connections/calls available, current utilization, amongst
	others. Peering Session-specific policies can change within the time it
	takes to establish a call.
	These policies can be SSP dependent or independent, creating the following
	peering policy definition:
	o SSP Independent or Dependent
	Session dependent Session
	independent
	6. Call Control and Media Control Deployment Options
	The peering functions can be deployed along the following two dimensions
	depending upon how the signaling and the media functions along with IP layer
	are implemented:
	Composed or Decomposed: Addresses the question whether the media must flow
	through the same physical and geographic elements as SIP dialogs and sessions.
	Centralized or Distributed: Addresses the question whether the logical and
	physical interconnections are in one geographical location or distributed to
	multiple physical locations on the SSP's network.
	In a composed model, SF and MF functions are implemented in one peering logical
	element.
	Provider A Provider B
	---------- . . ----------
	/ \ . . / \
	| | . _ . | |
	| +----+ . / \_ . +----+ |
	| | SF |<-----/ \------| SF | |
	| +-+--+ . /Transit\ . | | |
	| | | . / IP \ . | | |
	| +-+--+ . | Provider| . | | |
	| | MF |<~~~| (Option)|~~~~| MF | |
	| +----+ . \ / . +----+ |
	| | . \ __ _ / . | |
	\_________ / . . \________ _/
	---------- ----------
	--- Signal (SIP)
	~~~ Bearer (RTP/IP)
	... Scope of peering
	Figure 3: Decomposed v. Collapsed Peering
	The advantage of a collapsed peering architecture is that one-element solves
	all peering issues. Disadvantage examples of this architecture are single point
	of failure, bottleneck, and complex scalability.
	In a decomposed model, SF and MF are implemented in separate peering logical
	elements. SFs are implemented in a proxy and MFs are implemented in another
	logical element. The scaling of signaling versus scaling of media may differ
	between applications. Decomposing allows each to follow a separate migration
	path.
	This model allows the implementation of M:N model where one SF is associated
	with multiple peering MF and one peering MF is associated with multiple SFs.
	Generally, a vertical protocol associates the relationship between a SF and a
	MF. This architecture reduces the potential of a single point of failure. It
	allows separation of the policy decision point and the policy enforcement
	point. An example of disadvantages is the scaling complexity because of the M:N
	relationship and latency due to the vertical control messages between entities.
	7. Address space considerations
	Peering must occur in a common IP address space, which is defined by the		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 private		federation, which may be entirely on the public Internet, or some private
	address space. The origination or termination networks may or may not entirely		address space. The origination or termination networks may or may not entirely
	be in the same address space. If they are not, then a network address		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		translation (NAT) or similar may be needed before the signaling or media is
	presented correctly to the federation. The only requirement is that all		presented correctly to the federation. The only requirement is that all
	associated entities across the peering interface are reachable.		associated entities across the peering interface are reachable.
	8. Security Considerations		6. Security Considerations
	In all cases, cryptographic-based security should be maintained as an optional		In all cases, cryptographic-based security should be maintained as an optional
	requirement between peering providers conditioned on the presence or absence of		requirement between peering providers conditioned on the presence or absence of
	underlying physical security of SSP connections, e.g. within the same secure		underlying physical security of SSP connections, e.g. within the same secure
	physical building.		physical building.
	In order to maintain a consistent approach, unique and specialized security		In order to maintain a consistent approach, unique and specialized security
	requirements common for the majority of peering relationships, should be		requirements common for the majority of peering relationships, should be
	standardized within the IETF. These standardized methods may enable		standardized within the IETF. These standardized methods may enable
	capabilities such as dynamic peering relationships across publicly maintained		capabilities such as dynamic peering relationships across publicly maintained
	interconnections.		interconnections.
	9. IANA Considerations		7. IANA Considerations
	There are no IANA considerations at this time.		There are no IANA considerations at this time.
	10. Acknowledgments		8. Acknowledgments
	The working group thanks Sohel Khan for his initial architecture		The working group thanks Sohel Khan for his initial architecture
	draft that helped to initiate work on this draft.		draft that helped to initiate work on this draft.
	A significant portion of this draft is taken from [14] with		A significant portion of this draft is taken from [14] with
	permission from the author R. Mahy. The other important contributor		permission from the author R. Mahy. The other important contributor
	is Otmar Lendl. Special thanks to Jim McEachern for detailed comments and		is Otmar Lendl. Special thanks to Jim McEachern for detailed comments and
	feedback.		feedback.
	11. References		9. References
	11.1. Normative References		9.1. Normative References
	[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels",		[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels",
	BCP 14, RFC 2119, March 1997.		BCP 14, RFC 2119, March 1997.
	[2] Mealling, M. and R. Daniel, "The Naming Authority Pointer (NAPTR) DNS		[2] Mealling, M. and R. Daniel, "The Naming Authority Pointer (NAPTR) DNS
	Resource Record", RFC 2915, September 2000.		Resource Record", RFC 2915, September 2000.
	[3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson,		[3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson,
	J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation		J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation
	Protocol", RFC 3261, June 2002.		Protocol", RFC 3261, June 2002.
	skipping to change at page 17, line 5		skipping to change at page 12, line 5
	[10] ETSI TS 102 333: " Telecommunications and Internet converged Services		[10] ETSI TS 102 333: " Telecommunications and Internet converged Services
	and Protocols for Advanced Networking (TISPAN); Gate control protocol".		and Protocols for Advanced Networking (TISPAN); Gate control protocol".
	[11] Peterson, J., "enumservice registration for Session Initiation Protocol		[11] Peterson, J., "enumservice registration for Session Initiation Protocol
	(SIP) Addresses-of-Record", RFC 3764, April 2004.		(SIP) Addresses-of-Record", RFC 3764, April 2004.
	[12] Livingood, J. and R. Shockey, "IANA Registration for an		[12] Livingood, J. and R. Shockey, "IANA Registration for an
	Enumservice Containing PSTN Signaling Information", RFC 4769, November		Enumservice Containing PSTN Signaling Information", RFC 4769, November
	2006.		2006.
	11.2. Informative References		9.2. Informative References
	[13] Malas, D., "SPEERMINT Terminology", draft-ietf-speermint-terminology-16		[13] Malas, D., "SPEERMINT Terminology", draft-ietf-speermint-terminology-16
	(work in progress), February 2008.		(work in progress), February 2008.
	[14] Mule, J-F., "SPEERMINT Requirements for SIP-based VoIP Interconnection",		[14] Mule, J-F., "SPEERMINT Requirements for SIP-based VoIP Interconnection",
	draft-ietf-speermint-requirements-04.txt, February 2008.		draft-ietf-speermint-requirements-04.txt, February 2008.
	[15] Mahy, R., "A Minimalist Approach to Direct Peering", draft-		[15] Mahy, R., "A Minimalist Approach to Direct Peering", draft-
	mahy-speermint-direct-peering-02.txt, July 2007.		mahy-speermint-direct-peering-02.txt, July 2007.
	skipping to change at line 755		skipping to change at page 13, line 31
	Sohel Khan, Ph.D.		Sohel Khan, Ph.D.
	Comcast Cable Communications		Comcast Cable Communications
	USA		USA
	Email: sohel_khan@cable.comcast.com		Email: sohel_khan@cable.comcast.com
	Daryl Malas		Daryl Malas
	CableLabs		CableLabs
	Louisville, CO - USA		Louisville, CO - USA
	Email: d.malas@cablelabs.com		Email: d.malas@cablelabs.com
			Hadriel Kaplan
			Acme Packet
			Email: hkaplan@acmepacket.com
			Jason Livingood
			Comcast
			Email: Jason_livingood@cable.comcast.com
			David Schwartz
			Kayote Systems
			Email: david.schwartz@kayote.com
			Rich Shockey
			Unaffiliated
			Email: Richard@shockey.us
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