draft-ietf-speermint-architecture-07.txt   draft-ietf-speermint-architecture-08.txt 
Speermint Working Group R. Penno Speermint Working Group A.Uzelac(Ed.)
Internet Draft Juniper Networks Internet Draft Global Crossing
Intended status: Informational D. Malas Intended status: Informational
Expires: May 2009 CableLabs Expires: September 2009
S. Khan March 2, 2009
Comcast
A. Uzelac
Global Crossing
M. Hammer
Cisco Systems
November 3, 2008
SPEERMINT Peering Architecture SPEERMINT Peering Architecture
draft-ietf-speermint-architecture-07 draft-ietf-speermint-architecture-08
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Abstract
This document defines the SPEERMINT peering architecture, its This document is subject to BCP 78 and the IETF Trust's Legal
functional components and peering interface functions. It also Provisions Relating to IETF Documents
describes the steps taken to establish a session between two peering (http://trustee.ietf.org/license-info) in effect on the date of
domains in the context of the functions defined. publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document.
Conventions used in this document Abstract
The key words "must", "must NOT", "REQUIRED", "SHALL", "SHALL NOT", This document defines the SPEERMINT peering architecture, its functional
"should", "should NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this components and peering interface functions. It also describes the steps taken
document are to be interpreted as described in RFC-2119[1] to establish a session between two peering domains in the context of the
functions defined.
Table of Contents Table of Contents
1. Introduction...................................................3 1. Introduction...................................................3
2. Network Context................................................3 2. Network Context................................................3
3. Procedures.....................................................6 3. Reference SPEERMINT Architecture...............................4
4. Reference SPEERMINT Architecture...............................6 4. Procedures of Interdomain SSP Session Establishment............6
5. Recommended SSP Procedures.....................................8 5. Recommended SSP Procedures.....................................7
5.1. Originating SSP Procedures................................8 5.1. Originating SSP Procedures................................7
5.1.1. The Look-Up Function (LUF)...........................8 5.1.1. The Look-Up Function (LUF)...........................7
5.1.1.1. Target address analysis.........................8 5.1.1.1. Target address analysis.........................7
5.1.1.2. User ENUM Lookup................................9 5.1.1.2. End User ENUM Lookup............................8
5.1.1.3. Infrastructure ENUM lookup......................9 5.1.1.3. Infrastructure ENUM lookup......................8
5.1.2. Location Routing Function (LRF).....................10 5.1.2. Location Routing Function (LRF)......................8
5.1.2.1. Routing Table..................................10 5.1.2.1. SIP DNS Resolution..............................8
5.1.2.2. SIP DNS Resolution.............................10 5.1.2.2. Routing Table...................................9
5.1.2.3. SIP Redirect Server............................11 5.1.2.3. SIP Redirect Server.............................9
5.1.3. The Signaling Function (SF).........................11 5.1.3. The Signaling Function (SF)..........................9
5.1.3.1. Establishing a Trusted Relationship............11 5.1.3.1. Establishing a Trusted Relationship.............9
5.1.3.2. Sending the SIP request........................12 5.1.3.2. Sending the SIP request........................10
5.2. Terminating SSP Procedures...............................12 5.2. Terminating SSP Procedures...............................10
5.2.1. The Location Function (LF)..........................12 5.2.1. The Location Function (LF)..........................10
5.2.1.1. Publish ENUM records...........................12 5.2.1.1. Publish ENUM records...........................10
5.2.1.2. Publish SIP DNS records........................13 5.2.1.2. Publish SIP DNS records........................11
5.2.1.3. Subscribe Notify...............................13 5.2.1.3. Subscribe Notify...............................11
5.2.2. Signaling Function (SF).............................13 5.2.2. Signaling Function (SF).............................11
5.2.2.1. TLS............................................13 5.2.2.1. TLS............................................11
5.2.2.2. Receive SIP requests...........................13 5.2.2.2. Receive SIP requests...........................11
5.3. Target SSP Procedures....................................14 5.3. Target SSP Procedures....................................12
5.3.1. Signaling Function (SF).............................14 5.3.1. Signaling Function (SF).............................12
5.3.1.1. TLS............................................14 5.3.1.1. TLS............................................12
5.3.1.2. Receive SIP requests...........................14 5.3.1.2. Receive SIP requests...........................12
5.4. Media Function (MF)......................................14 5.4. Media Function (MF)......................................12
5.5. Policy Considerations....................................14 5.5. Policy Considerations....................................12
6. Call Control and Media Control Deployment Options.............15 6. Call Control and Media Control Deployment Options.............13
7. Address space considerations..................................17 7. Address space considerations..................................14
8. Security Considerations.......................................17 8. Security Considerations.......................................15
9. IANA Considerations...........................................17 9. IANA Considerations...........................................15
10. Acknowledgments..............................................17 10. Acknowledgments..............................................15
11. References...................................................18 11. References...................................................16
11.1. Normative References....................................18 11.1. Normative References....................................16
11.2. Informative References..................................19 11.2. Informative References..................................17
Author's Addresses...............................................20 Author's Addresses...............................................18
Intellectual Property Statement..................................20
Disclaimer of Validity...........................................21
1. Introduction 1. Introduction
The objective of this document is to define a reference peering The objective of this document is to define a reference peering architecture in
architecture in the context of Session PEERing for Multimedia the context of Session PEERing for Multimedia INTerconnect (SPEERMINT). In this
INTerconnect (SPEERMINT). In this process, we define the peering process, we define the peering reference architecture, its functional
reference architecture (reference, for short), it's functional components, and peering interface functions from the perspective of a SIP
components, and peering interface functions from the perspective of Service provider's (SSP) network.
a SIP Service provider's (SSP) network.
This architecture allows the interconnection of two SSPs in layer 5 This architecture allows the interconnection of two SSPs in layer 5 peering as
peering as defined in the SPEERMINT Requirements [13] and defined in the SPEERMINT Requirements [14] and Terminology [13] documents.
Terminology [12] documents.
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
figures in this document do not show routers so that the focus is on this document do not show routers so that the focus is on Layer 5 protocol
Layer 5 protocol aspects. aspects.
This document uses terminology defined in the SPEERMINT Terminology This document uses terminology defined in the SPEERMINT Terminology document
document [12], so the reader should be familiar with all the terms [13], so the reader should be familiar with all the terms defined there.
defined there.
2. Network Context In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are
to be interpreted as described in [RFC2119].
Figure 1 shows an example network context. Two SSPs can form a Layer 2. Network Context
5 peering over either the public Internet or private Layer3
networks. In addition, two or more providers may form a SIP (Layer
5) federation [13] on either the public Internet or private Layer 3
networks. This document does not make any assumption whether the SIP
providers directly peer to each other or through Layer 3 transit
network as per use case of [16].
Note that Figure 1 allows for the following potential SPEERMINT Figure 1 allows for the following potential SPEERMINT peering scenarios:
peering scenarios:
o Enterprise to Enterprise across the public Internet o Enterprise to Enterprise across the public Internet
o Enterprise to SSP across the public Internet o Enterprise to SSP across the public Internet
o SSP 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 enterprise across a private Layer 3 network
o Enterprise to SSP 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 o SSP to SSP across a private Layer 3 network
The members of a federation may jointly use a set of functions such
as location function, signaling function, media function, ENUM
database or SIP Registrar, SIP proxies, and/or functions that
synthesize various SIP and non-SIP based applications. Similarly,
two SSPs may jointly use a set of functions. The functions can be
either public or private.
+-------------------+ +-------------------+
| | | |
| Public | | Public |
| SIP | | SIP |
| Peering | | Peering |
| | | |
+-------------------+ +-------------------+
| |
----- -----
+-----------+ / \ +-----------+ +-----------+ / \ +-----------+
skipping to change at page 5, line 46 skipping to change at page 4, line 36
| SSP G |-----------\ /-----------| SSP H | | SSP G |-----------\ /-----------| SSP H |
| | -- -- | | | | -- -- | |
+-----------+ \____/ +-----------+ +-----------+ \____/ +-----------+
| |
+-------------------+ +-------------------+
| Private | | Private |
| SIP | | SIP |
| Peering | | Peering |
| | | |
+-------------------+ +-------------------+
Figure 1: SPEERMINT Network Context Figure 1: SPEERMINT Network Context
3. Procedures 3. Reference SPEERMINT Architecture
This document assumes that in order for call to be establish from a
UAC end user in the initiating peer's network to a UAS in the
receiving peer's network the following steps are taken:
1. The analysis of the target address.
. If the target address represents an intra-SSP resource, the
behavior is out-of-scope with respect to this draft.
2. the determination of the target SSP,
3. the determination of the SF next-hop in the target SSP,
4. the enforcement of authentication and potentially other
policies,
5. the determination of the UAS,
6. the session establishment,
7. the transfer of media which could include voice, video, text
and others,
8. and the session termination.
The originating SSP would likely perform steps 1-4, and the
terminating SSP would likely perform steps 4-5.
In the case the target SSP is different from the terminating SSP it
would repeat steps 1-4. This is reflected in Figure 2 that shows the
target SSP with its own peering functions.
4. Reference SPEERMINT Architecture
Figure 2 depicts the SPEERMINT architecture and logical functions Figure 2 depicts the SPEERMINT architecture and logical functions that form the
that form the peering between two SSPs. peering between two SSPs.
+------+ +------+
| DNS, | | DNS, |
+---------->| Db, |<---------+ +---------->| Db, |<---------+
| | etc | | | | etc | |
| +------+ | | +------+ |
| | | |
------|-------- -------|------- ------|-------- -------|-------
/ v \ / v \ / v \ / v \
| +--LUF-+ | | +--LUF-+ | | +--LUF-+ | | +--LUF-+ |
skipping to change at page 7, line 41 skipping to change at page 5, line 41
| SSP | | SSP | | SSP | | SSP |
| +---MF--+ +---MF--+ | | +---MF--+ +---MF--+ |
| | | | | | | | | | | |
| | DBE | | DBE | | | | DBE | | DBE | |
| | | | | | | | | | | |
| +---MF--+ +---MF--+ | | +---MF--+ +---MF--+ |
\ / \ / \ / \ /
--------------- --------------- --------------- ---------------
Figure 2: Reference SPEERMINT Architecture Figure 2: Reference SPEERMINT Architecture
The procedures presented in section 3 are implemented by a set of The following procedures are implemented by a set of peering functions:
peering functions:
The Look-Up Function (LUF) provides a mechanism for determining for The Look-Up Function (LUF) provides a mechanism for determining for a given
a given request the target domain to which the request should be request the target domain to which the request should be routed.
routed.
The Location Routing Function (LRF) determines for the target domain The Location Routing Function (LRF) determines for the target domain of a given
of a given request the location of the SF in that domain and request the location of the SF in that domain and optionally develops other
optionally develops other Session Establishment Data (SED) required Session Establishment Data (SED) required to route the request to that domain.
to route the request to that domain.
Signaling Function (SF): Purpose is to perform SIP call routing, to The Signaling Function (SF) provides SIP call routing, to optionally perform
optionally perform termination and re-initiation of call, to termination and re-initiation of call, to optionally implement security and
optionally implement security and policies on SIP messages, and to policies on SIP messages, and to assist in discovery/exchange of parameters to
assist in discovery/exchange of parameters to be used by the Media be used by the Media Function (MF).
Function (MF).
Media Function (MF): Purpose is to perform media related function The Media Function (MF) provides media related functions such as media
such as media transcoding and media security implementation between transcoding, topology hiding and media security implementation between two
two SIP providers. SSPs.
The intention of defining these functions is to provide a framework The intention of defining these functions is to provide a framework for design
for design segmentation and allow each one to evolve independently. segmentation and allow each one to evolve independently.
4. Procedures of Interdomain SSP Session Establishment
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
following steps are taken:
1. analyze the target address.
a. If the target address represents an intra-SSP resource, the
behavior is out-of-scope with respect to this draft.
2. determine the target SSP (LUF)
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,
7. transfer of media which could include voice, video, text and others,
8. terminate the session (BYE)
The originating SSP would likely perform steps 1-4, and the target SSP would
likely perform steps 4-5.
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.
5. Recommended SSP Procedures 5. Recommended SSP Procedures
This section describes the functions in more detail and provides This section describes the functions in more detail and provides some
some recommendations on the role they would play in a SIP call in a recommendations on the role they would play in a SIP call in a Layer 5 peering
Layer 5 peering scenario. scenario.
Some of the information in the chapter is taken from [14] and is put Some of the information in the section is taken from [14] and is put here for
here for continuity purposes. continuity purposes.
5.1. Originating SSP Procedures 5.1. Originating SSP Procedures
5.1.1. The Look-Up Function (LUF) 5.1.1. The Look-Up Function (LUF)
Purpose is to determine the SF of the target domain of a given Purpose is to determine the SF of the target domain of a given request and
request and optionally develop Session Establishment Data (SED) optionally develop Session Establishment Data.
[12].
5.1.1.1. Target address analysis 5.1.1.1. Target address analysis
When the initiating SSP receives a request to communicate, it When the originating SSP receives a request to communicate, it analyzes the
analyzes the target URI to determine whether the call needs to be target URI to determine whether the call needs to be routed internal or
terminated internally or externally to its network. The analysis external to its network. The analysis method is internal to the SSP; thus,
method is internal to the SSP; thus, outside the scope of SPEERMINT. outside the scope of SPEERMINT. Note that the SSP may also consult any manner
Note that the SSP is free to consult any manner of private data of private data sources to make this determination.
sources to make this determination.
If the target address does not represent a resource inside the If the target address does not represent a resource inside the originating
initiating SSP's administrative domain or federation of domains, the SSP's administrative domain or federation of domains, the originating SSP
initiating SSP resolves the call routing data by using the Location resolves the call routing data by using the Location Routing Function (LRF).
Routing Function (LRF).
For example, if the request to communicate is for an im: or pres: For example, if the request to communicate is for an im: or pres: URI type, the
URI type, the initiating peer follows the procedures in [8]. If the originating SSP follows the procedures in [8]. If the highest priority
highest priority supported URI scheme is sip: or sips:, the supported URI scheme is sip: or sips: the originating SSP skips to SIP DNS
initiating peer skips to SIP DNS resolution in Section 5.1.3. resolution in Section 5.1.3. Likewise, if the target address is already a sip:
Likewise, if the target address is already a sip: or sips: URI in an or sips: URI in an external domain, the originating SSP skips to SIP DNS
external domain, the initiating peer skips to SIP DNS resolution in resolution in Section 5.1.2.1.
Section 5.1.2.2.
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
peer may need to perform some form of number plan mapping according to perform some form of number plan mapping according to local policy. For
to local policy. For example, in the United States, a dial string example, in the United States, a dial string beginning "011 44" could be
beginning "011 44" could be converted to "+44", or in the United converted to "+44", or in the United Kingdom "00 1" could be converted to "+1".
Kingdom "00 1" could be converted to "+1". Once the peer has an Once the SSP has an E.164 address, it can use ENUM.
E.164 address, it can use ENUM.
5.1.1.2. User ENUM Lookup 5.1.1.2. End User ENUM Lookup
If an external E.164 address is the target, the initiating peer If an external E.164 address is the target, the originating SSP consults the
consults the public "User ENUM" rooted at e164.arpa, according to public "User ENUM" rooted at e164.arpa, according to the procedures described
the procedures described in RFC 3761. The peer must query for the in RFC 3761. The SSP must query for the "E2U+sip" enumservice as described in
"E2U+sip" enumservice as described in RFC 3764 [11], but MAY check RFC 3764 [11], but MAY check for other enumservices. The originating SSP MAY
for other enumservices. The initiating peer MAY consult a cache or consult a cache or alternate representation of the ENUM data rather than actual
alternate representation of the ENUM data rather than actual DNS DNS queries. Also, the SSP may skip actual DNS queries if the originating SSP
queries. Also, the peer may skip actual DNS queries if the is sure that the target address country code is not represented in e164.arpa.
initiating peer is sure that the target address country code is not If a sip: or sips: URI is chosen the SSP skips to Section 5.1.6.
represented in e164.arpa. If a sip: or sips: URI is chosen the peer
skips to Section 5.1.6.
If an im: or pres: URI is retrieved based on an "E2U+im" [10] or If an im: or pres: URI is chosen for based on an "E2U+im" [8] or "E2U+pres" [9]
"E2U+pres" [9] enumserver, the peer follows the procedures for enumserver, the SSP follows the procedures for resolving these URIs to URIs for
resolving these URIs to URIs for specific protocols such a SIP or specific protocols such a SIP or XMPP as described in the previous section.
XMPP as described in the previous section.
5.1.1.3. Infrastructure ENUM lookup 5.1.1.3. Infrastructure ENUM lookup
Next the initiating peer checks for a carrier-of-record in a carrier An originating SSP may check for a carrier-of-record in an Infrastructure ENUM
ENUM domain according to the procedures described in [12]. As in domain according to the procedures described in [12]. As in the previous step,
the previous step, the peer may consult a cache or alternate the SSP may consult a cache or alternate representation of the ENUM data in
representation of the ENUM data in lieu of actual DNS queries. The lieu of actual DNS queries. The SSP first checks for records for the "E2U+sip"
peer first checks for records for the "E2U+sip" enumservice, then enumservice, then for the "E2U+pstn" enumservice as defined in [21]. If a
for the "E2U+pstn" enumservice as defined in [21]. If a terminal terminal record is found with a sip: or sips: URI, the SSP skips to Section
record is found with a sip: or sips: URI, the peer skips to Section 5.1.2.1. , otherwise the SSP continues processing according to the next
5.1.2.2. , otherwise the peer continues processing according to the section.
next section.
5.1.2. Location Routing Function (LRF) 5.1.2. Location Routing Function (LRF)
The LRF of an Initiating SSP analyzes target address and discovers The LRF of an Originating SSP analyzes target address and target domain
the next hop signaling function (SF) in a peering relationship. The identified by the LUF, and discovers the next hop signaling function (SF) in a
resource to determine the SF of the target domain might be provided peering relationship. The resource to determine the SF of the target domain
by a third-party as in the assisted-peering case. might be provided by a third-party as in the assisted-peering case.
5.1.2.1. Routing Table
If there is no user ENUM records and the initiating peer cannot 5.1.2.1. SIP DNS Resolution
discover the carrier-of-record or if the initiating peer cannot
reach the carrier-of-record via SIP peering, the initiating peer
still needs to deliver the call to the PSTN or reject it. Note that
the initiating peer may still forward the call to another SSP for
PSTN gateway termination by prior arrangement using the routing
table.
If so, the initiating peer may rewrite the Request-URI to address Once a sip: or sips: in an external domain is identified as the target, the
the gateway resource in the target SSP's domain and may forward the originating SSP may apply local policy to decide whether forwarding requests to
request on to that SSP using the procedures described in the the target domain is acceptable. The originating SSP uses the procedures in
remainder of these steps. RFC 3263 [4] Section 4 to determine 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. Note that these
are queries of records in the global DNS.
Alternatively to Request-URI re-writing, the initiating peer may When communicating with another SSP, entities compliant to this document should
populate the Route header with the address of the gateway resource select a TLS-protected transport for communication from the originating SSP to
in the target SSP's domain and forward the request on to that SSP the receiving SSP if available.
using the procedures described in the remainder of these steps, but
applied to the Route header.
5.1.2.2. SIP DNS Resolution 5.1.2.2. Routing Table
Once a sip: or sips: in an external domain is selected as the If there are no End User ENUM records and the Originating SSP cannot discover
target, the initiating peer may apply local policy to decide whether the carrier-of-record or if the Originating SSP cannot reach the carrier-of-
forwarding requests to the target domain is acceptable. If so, the record via SIP peering, the Originating SSP may deliver the call to the PSTN or
initiating peer uses the procedures in RFC 3263 [4] Section 4 to reject it. Note that the originating SSP may forward the call to another SSP
determine how to contact the receiving peer. To summarize the RFC for PSTN gateway termination by prior arrangement using the routing table.
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.
Note that these are queries of records in the global DNS.
When communicating with another SSP, entities compliant to this If so, the originating SSP rewrites the Request-URI to address the gateway
document should select a TLS-protected transport for communication resource in the target SSP's domain and MAY forward the request on to that SSP
from the initiating peer to the receiving peer if available. Note using the procedures described in the remainder of these steps.
that this is a single-hop requirement.
5.1.2.3. SIP Redirect Server 5.1.2.3. SIP Redirect Server
A SIP Redirect Server may help in resolving the current address of A SIP Redirect Server using 3XX SIP Redirect is another option in resolving the
the next-hop SF in the target domain. next-hop SF of the target domain.
5.1.3. The Signaling Function (SF) 5.1.3. The Signaling Function (SF)
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
messages, to optionally perform termination and re-initiation of a as optionally implement security and policies on SIP messages, and to assist in
call, to optionally implement security and policies on SIP messages, discovery/exchange of parameters to be used by the Media Function (MF).
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 The signaling function performs the routing of SIP messages. The optional
optional termination and re-initiation of calls are performed by the termination and re-initiation of calls may be performed by the signaling path
signaling path border element (SBE). Session Border Element (SBE).
Optionally, a SF may perform additional functions such as Session Optionally, a SF may perform additional functions such as Session Admission
Admission Control, SIP Denial of Service protection, SIP Topology Control, SIP Denial of Service protection, SIP Topology Hiding, SIP header
Hiding, SIP header normalization, and SIP security, privacy and normalization, and SIP security, privacy and encryption.
encryption.
The SF 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 media type, bandwidth, and type of codec; then, communicate this information to
information to the media function. Signaling function may optionally the media function. Signaling function may optionally communicate with the
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 5.1.3.1. Establishing a Trusted Relationship
Depending on the security needs and trust relationship between SSPs, Depending on the security needs and trust relationships between SSPs, different
different security mechanism can be used to establish SIP calls. security mechanism can be used to establish SIP calls. These are discussed in
These are discussed in the following subsections. the following subsections.
5.1.3.1.1. TLS connection 5.1.3.1.1. TLS connection
Once a transport, port, and address are found, the initiating SSP Once a transport, port, and address are found, the originating SSP will open or
will open or find a reusable TLS connection to the peer. The find a reusable TLS connection to the peer. The procedures to authenticate the
procedures to authenticate the SSP's target domain is specified in SSP's target domain is specified in [24]
[24]
5.1.3.1.2. IPSec 5.1.3.1.2. TLS
In certain deployments, the use of IPSec between the signaling If the trust relationship was established through TLS, the originating SSP can
functions of the originating and terminating domains can be used as optionally verify and assert the senders identity using the SIP Identity
a security mechanism instead of TLS. mechanism.
5.1.3.1.3. Co-Location 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.
In this scenario, the SFs are co-located in a physically secure 5.1.3.1.3. IPSec
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.
5.1.3.2. Sending the SIP request 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
of TLS.
Once a trust relationship between the peers is established, the 5.1.3.1.4. Co-Location
initiating peer sends the request.
5.1.3.2.1. TLS 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.
If the trust relationship was established through TLS, the 5.1.3.2. Sending the SIP request
initiating peer can optionally verify and assert the sender's
identity using the SIP Identity mechanism.
In addition, new requests should contain a valid Identity and Once a trust relationship between the peers is established, the originating SSP
Identity-Info header as described in [12]. The Identity-Info header sends the request.
must present a domain name that is represented in the certificate
provided when establishing the TLS connection over which the request
is sent. The initiating peer should include an Identity header on
in-dialog requests as well if the From header field value matches an
identity the initiating peer is willing to assert.
5.2. Terminating SSP Procedures 5.2. Terminating SSP Procedures
5.2.1. The Location Function (LF) 5.2.1. The Location Function (LF)
5.2.1.1. Publish ENUM records 5.2.1.1. Publish ENUM records
The receiving peer should publish "E2U+SIP" and "E2U+pstn" records The receiving SSP should participate by publishing "E2U+sip" and "E2U+pstn"
with sip: or sips: URIs wherever a public carrier ENUM root is records with sip: or sips: URIs wherever a public Infrastructure ENUM root is
available. In the event that a public root is not available, a available. This assumes that the receiving SSP wants to peer by default. When
publishing to a common ENUM registry with the originating peer will the receiving SSP does not want to accept traffic from specific originating
suffice. SSPs, it may still reject requests on a call-by-call basis.
This assumes that the receiving peer wants to peer by default. When
the receiving peer does not want to accept traffic from specific
initiating peers, it may still reject requests on a call-by-call
basis.
5.2.1.2. Publish SIP DNS records 5.2.1.2. Publish SIP DNS records
To receive peer requests, the receiving peer must ensure that it To receive SSP requests, the receiving SSP must insure that it publishes
publishes appropriate NAPTR, SRV, and address (A and/or AAAA) appropriate NAPTR, SRV, and address (A and/or AAAA) records in the LF relevant
records in the LF relevant to the originating peer's SF. to the SSP's SF.
5.2.1.3. Subscribe Notify 5.2.1.3. Subscribe Notify
A policy notification function may also be optionally implemented by Policies function may also be optionally implemented by dynamic subscribe,
dynamic subscribe, notify, and exchange of policy information and notify, and exchange of policy information and feature information among SSPs
feature information among SSPs [21]. [21].
5.2.2. Signaling Function (SF) 5.2.2. Signaling Function (SF)
5.2.2.1. TLS 5.2.2.1. TLS
When the receiving peer receives a TLS client hello, it responds When the receiving SSP receives a TLS client hello, it responds with its
with its certificate. The target SSP certificate should be valid certificate. The Target SSP certificate should be valid and rooted in a well-
and rooted in a well-known certificate authority. The procedures to known certificate authority. The procedures to authenticate the SSP's
authenticate the SSP's originating domain are specified in [24]. originating domain are specified in [24].
The terminating SF 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
and that the domain in the From header corresponds to one of the the domain in the From header corresponds to one of the domains in the TLS
domains in the TLS client certificate. client certificate.
5.2.2.2. Receive SIP requests 5.2.2.2. Receive SIP requests
Once a trust relationship is established, the receiving peer is Once a trust relationship is established, the Target SSP is prepared to receive
prepared to receive incoming SIP requests. For new requests (dialog incoming SIP requests. For new requests (dialog forming or not) the receiving
forming or not) the receiving peer verifies if the target (request- SSP verifies if the target (request-URI) is a domain that for which it is
URI) is a domain that for which it is responsible. For these responsible. For these requests, there should be no remaining Route header
requests, there should be no remaining Route header field values. field values. For in-dialog requests, the receiving SSP can verify that it
For in-dialog requests, the receiving peer can verify that it
corresponds to the top-most Route header field value. corresponds to the top-most Route header field value.
The receiving peer may reject incoming requests due to local policy. The receiving SSP may reject incoming requests due to local policy. When a
When a request is rejected because the initiating peer is not request is rejected because the originating SSP is not authorized to peer, the
authorized to peer, the receiving peer should respond with a 403 receiving SSP should respond with a 403 response with the reason phrase
response with the reason phrase "Unsupported Peer". "Unsupported Peer".
5.3. Target SSP Procedures 5.3. Target SSP Procedures
5.3.1. Signaling Function (SF) 5.3.1. Signaling Function (SF)
5.3.1.1. TLS 5.3.1.1. TLS
When the receiving peer receives a TLS client hello, it responds When the receiving SSP receives a TLS client hello, it responds with its
with its certificate. The target SSP certificate should be valid certificate. The Target SSP's certificate should be valid and rooted in a
and rooted in a well-known certificate authority. The procedures to well-known certificate authority. The procedures to authenticate the SSP's
authenticate the SSP's originating domain are specified in [24]. originating domain are specified in [24].
If the requests should contain a valid Identity and Identity-Info If the requests should contain a valid Identity and Identity-Info header as
header as described in [12] the target SF verifies that the Identity described in [24] the target SF verifies that the Identity header is valid,
header is valid, corresponds to the message, corresponds to the corresponds to the message, corresponds to the Identity-Info header, and that
Identity-Info header, and that the domain in the From header the domain in the From header corresponds to one of the domains in the TLS
corresponds to one of the domains in the TLS client certificate. client certificate.
5.3.1.2. Receive SIP requests 5.3.1.2. Receive SIP requests
The procedures of the SF of the target SSP are the same as the ones The procedures of the SF of the target SSP are the same as the ones described
described in section 5.2.2.2 with the addition that it might in section 5.2.2.2 with the addition that it might establish a connection to
establish a connection to another target SSP, and in this case use another target SSP, and in this case use the procedures recommended to an
the procedures recommended to an originating SSP (section 5.1). originating SS (section 5.1).
5.4. Media Function (MF) 5.4. Media Function (MF)
The purpose of the MF is to perform media related functions such as The purpose of the MF is to perform media related functions such as media
media transcoding and media security implementation between two transcoding and media security implementation between two SSPs.
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)
(e.g., G.711) to another (e.g., EvRC). Additionally, the MF may to another (e.g., EvRC). Additionally, the MF may perform media relaying,
perform media relaying, media security, privacy, and encryption. media security, privacy, and encryption.
5.5. Policy Considerations 5.5. Policy Considerations
In the context of the SPEERMINT working group when two SSPs peer, In the context of the SPEERMINT working group when two SSPs peer, there MAY be
there MAY be a desire to exchange peering policy information a desire to exchange peering policy information dynamically. There are
dynamically. There are specifications in progress in the SIPPING specifications in progress in the SIPPING working group to define policy
working group to define policy exchange between an UA and a domain exchange between an UA and a domain [23] and providing profile data to SIP user
[23] and providing profile data to SIP user agents [24] These agents [24] These considerations borrow from both.
considerations borrow from both.
Following the terminology introduced in [12], this package uses the Following the terminology introduced in [12], this package uses the terms
terms Peering Session-Independent and Session-Specific policies in Peering Session-Independent and Session-Specific policies in the following
the following context. context.
o Peering Session-Independent policies include Diffserv Marking, o Peering Session-Independent policies include Diffserv Marking, Policing,
Policing, Session Admission Control, and domain reachabilities, Session Admission Control, and domain reachabilities, amongst others. The
amongst others. The time period between Peering Session- time period between Peering Session-Independent policy changes is much
Independent policy changes is much greater than the time it 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. takes to establish a call.
o Peering Session-Specific polices includes supported These policies can be SSP dependent or independent, creating the following
connection/call rate, total number of connections/calls peering policy definition:
available, current utilization, amongst others. Peering
Session-specific policies can change within the time it takes
to establish a call.
Likewise, but orthogonal to session dependency, an SSP may have o SSP Independent or Dependent
policies that may be peer-dependent or peer-independent. That is, Session dependent Session
the session-dependent and session-independent policies may by independent
further sub-divided and modified by additional controls that depend
on which peer SSP or federation with which communications is being
established.
6. Call Control and Media Control Deployment Options 6. Call Control and Media Control Deployment Options
The peering functions can be deployed along the following two The peering functions can be deployed along the following two dimensions
dimensions depending upon how the signaling and the media functions depending upon how the signaling and the media functions along with IP layer
along with IP layer are implemented: are implemented:
Composed or Decomposed: Addresses the question whether the media Composed or Decomposed: Addresses the question whether the media must flow
must flow through the same physical and geographic elements as SIP through the same physical and geographic elements as SIP dialogs and sessions.
dialogs and sessions.
Centralized or Distributed: Addresses the question whether the Centralized or Distributed: Addresses the question whether the logical and
logical and physical interconnections are in one geographical physical interconnections are in one geographical location or distributed to
location or distributed to multiple physical locations on the SSP's multiple physical locations on the SSP's network.
network.
In a composed model, SF and MF functions are implemented in one In a composed model, SF and MF functions are implemented in one peering logical
peering logical element. element.
Provider A Provider B Provider A Provider B
---------- . . ---------- ---------- . . ----------
/ \ . . / \ / \ . . / \
| | . _ . | | | | . _ . | |
| +----+ . / \_ . +----+ | | +----+ . / \_ . +----+ |
| | SF |<-----/ \------| SF | | | | SF |<-----/ \------| SF | |
| +-+--+ . /Transit\ . | | | | +-+--+ . /Transit\ . | | |
| | | . / IP \ . | | | | | | . / IP \ . | | |
| +-+--+ . \ Provider| . | | | | +-+--+ . | Provider| . | | |
| | MF |<~~~~\(Option)|~~~~| MF | | | | MF |<~~~| (Option)|~~~~| MF | |
| +----+ . \ / . +----+ | | +----+ . \ / . +----+ |
| | . \__ _/ . | | | | . \__ _/ . | |
\_________ / . . \________ _/ \_________ / . . \________ _/
---------- ---------- ---------- ----------
--- Signal (SIP) --- Signal (SIP)
~~~ Bearer (RTP/IP) ~~~ Bearer (RTP/IP)
... Scope of peering ... Scope of peering
Figure 3: Decomposed v. Collapsed Peering Figure 3: Decomposed v. Collapsed Peering
The advantage of a collapsed peering architecture is that one- The advantage of a collapsed peering architecture is that one-element solves
element solves all peering issues. Disadvantage examples of this all peering issues. Disadvantage examples of this architecture are single point
architecture are single point of failure, bottleneck, and complex of failure, bottleneck, and complex scalability.
scalability.
In a decomposed model, SF and MF are implemented in separate peering In a decomposed model, SF and MF are implemented in separate peering logical
logical elements. SFs are implemented in a proxy and MFs are elements. SFs are implemented in a proxy and MFs are implemented in another
implemented in another logical element. The scaling of signaling logical element. The scaling of signaling versus scaling of media may differ
versus scaling of media may differ between applications. between applications. Decomposing allows each to follow a separate migration
Decomposing allows each to follow a separate migration path. path.
This model allows the implementation of M:N model where one SF is This model allows the implementation of M:N model where one SF is associated
associated with multiple peering MF and one peering MF is associated with multiple peering MF and one peering MF is associated with multiple SFs.
with multiple SFs. Generally, a vertical protocol associates the Generally, a vertical protocol associates the relationship between a SF and a
relationship between a SF and a MF. This architecture reduces the MF. This architecture reduces the potential of a single point of failure. It
potential of a single point of failure. It allows separation of the allows separation of the policy decision point and the policy enforcement
policy decision point and the policy enforcement point. An example point. An example of disadvantages is the scaling complexity because of the M:N
of disadvantages is the scaling complexity because of the M:N relationship and latency due to the vertical control messages between entities.
relationship and latency due to the vertical control messages
between entities.
7. 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
the federation, which may be entirely on the public Internet, or federation, which may be entirely on the public Internet, or some private
some private address space. The origination or termination networks address space. The origination or termination networks may or may not entirely
may or may not entirely be in the same address space. If they are be in the same address space. If they are not, then a network address
not, then a network address translation (NAT) or similar function translation (NAT) or similar may be needed before the signaling or media is
may be needed before the signaling or media is presented correctly presented correctly to the federation. The only requirement is that all
to the federation. The only requirement is that all associated associated entities across the peering interface are reachable.
entities across the peering interface are reachable.
8. Security Considerations 8. Security Considerations
In all cases, cryptographic-based security should be maintained as In all cases, cryptographic-based security should be maintained as an optional
an optional requirement between peering providers conditioned on the requirement between peering providers conditioned on the presence or absence of
presence or absence of underlying physical security of peer underlying physical security of SSP connections, e.g. within the same secure
connections, e.g. within the same secure physical building. physical building.
In order to maintain a consistent approach, unique and specialized
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.
TODO: Address RFC-3552 BCP items. In order to maintain a consistent approach, unique and specialized 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.
9. IANA Considerations 9. IANA Considerations
There are no IANA considerations at this time. There are no IANA considerations at this time.
10. Acknowledgments 10. 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 portion of this draft is taken from [14] with permission from the A significant portion of this draft is taken from [14] with
author R. Mahy. The other important contributor is Otmar Lendl. permission from the author R. Mahy. The other important contributor
is Otmar Lendl. Special thanks to Jim McEachern for detailed comments and
feedback.
References 11. References
10.1. Normative References 11.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels",
Requirement Levels", BCP 14, RFC 2119, March 1997. BCP 14, RFC 2119, March 1997.
[2] Mealling, M. and R. Daniel, "The Naming Authority Pointer [2] Mealling, M. and R. Daniel, "The Naming Authority Pointer (NAPTR) DNS
(NAPTR) DNS Resource Record", RFC 2915, September 2000. Resource Record", RFC 2915, September 2000.
[3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., [3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson,
Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation
Session Initiation Protocol", RFC 3261, June 2002. Protocol", RFC 3261, June 2002.
[4] Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol [4] Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol (SIP):
(SIP): Locating SIP Servers", RFC 3263, June 2002. Locating SIP Servers", RFC 3263, June 2002.
[5] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., and [5] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., and T.
T. Wright, "Transport Layer Security (TLS) Extensions", RFC Wright, "Transport Layer Security (TLS) Extensions", RFC 4366, April
4366, April 2006. 2006.
[6] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, [6] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A
"RTP: A Transport Protocol for Real-Time Applications", STD Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July
64, RFC 3550, July 2003. 2003.
[7] Peterson, J., Liu, H., Yu, J., and B. Campbell, "Using E.164 [7] Peterson, J., Liu, H., Yu, J., and B. Campbell, "Using E.164 numbers
numbers with the Session Initiation Protocol (SIP)", RFC 3824, with the Session Initiation Protocol (SIP)", RFC 3824, June 2004.
June 2004.
[8] Peterson, J., "Address Resolution for Instant Messaging and [8] Peterson, J., "Address Resolution for Instant Messaging and
Presence",RFC 3861, August 2004. Presence",RFC 3861, August 2004.
[9] Peterson, J., "Telephone Number Mapping (ENUM) Service [9] Peterson, J., "Telephone Number Mapping (ENUM) Service Registration for
Registration for Presence Services", RFC 3953, January 2005. Presence Services", RFC 3953, January 2005.
[10] ETSI TS 102 333: " Telecommunications and Internet converged [10] ETSI TS 102 333: " Telecommunications and Internet converged Services
Services and Protocols for Advanced Networking (TISPAN); Gate and Protocols for Advanced Networking (TISPAN); Gate control protocol".
control protocol".
[11] Peterson, J., "enumservice registration for Session Initiation [11] Peterson, J., "enumservice registration for Session Initiation Protocol
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, Enumservice Containing PSTN Signaling Information", RFC 4769, November
November 2006. 2006.
10.2. Informative References 11.2. Informative References
[13] Malas, D., "SPEERMINT Terminology", draft-ietf-speermint- [13] Malas, D., "SPEERMINT Terminology", draft-ietf-speermint-terminology-16
terminology-16 (work in progress), February 2008. (work in progress), February 2008.
[14] Mule, J-F., "SPEERMINT Requirements for SIP-based VoIP [14] Mule, J-F., "SPEERMINT Requirements for SIP-based VoIP Interconnection",
Interconnection", draft-ietf-speermint-requirements-04.txt, draft-ietf-speermint-requirements-04.txt, February 2008.
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.
[16] Penno, R., et al., "SPEERMINT Routing Architecture Message [16] Penno, R., et al., "SPEERMINT Routing Architecture Message
Flows", draft-ietf-speermint-flows-02.txt", April 2007. Flows", draft-ietf-speermint-flows-02.txt", April 2007.
[17] Houri, A., et al., "RTC Provisioning Requirements", draft- [17] Houri, A., et al., "RTC Provisioning Requirements", draft-
houri-speermint-rtc-provisioning-reqs-00.txt, June, 2006. houri-speermint-rtc-provisioning-reqs-00.txt, June, 2006.
[18] Habler, M., et al., "A Federation based VOIP Peering [18] Habler, M., et al., "A Federation based VOIP Peering
Architecture", draft-lendl-speermint-federations-03.txt, Architecture", draft-lendl-speermint-federations-03.txt, September 2006.
September 2006.
[19] Mahy, R., "A Telephone Number Mapping (ENUM) Service [19] Mahy, R., "A Telephone Number Mapping (ENUM) Service
Registration for Instant Messaging (IM) Services", draft-ietf- Registration for Instant Messaging (IM) Services", draft-ietf-
enum-im-service-03 (work in progress), March 2006. enum-im-service-03 (work in progress), March 2006.
[20] Haberler, M. and R. Stastny, "Combined User and Carrier ENUM [20] Haberler, M. and R. Stastny, "Combined User and Carrier ENUM in the
in the e164.arpa tree", draft-haberler-carrier-enum-03 (work e164.arpa tree", draft-haberler-carrier-enum-03 (work in progress),
in progress), March 2006. March 2006.
[21] Penno, R., Malas D., and Melampy, P., "A Session Initiation [21] Penno, R., Malas D., and Melampy, P., "A Session Initiation
Protocol (SIP) Event package for Peering", draft-penno- Protocol (SIP) Event package for Peering", draft-penno-sipping-peering-
sipping-peering-package-00 (work in progress), September 2006. package-00 (work in progress), September 2006.
[22] Hollander, D., Bray, T., and A. Layman, "Namespaces in XML", [22] Hollander, D., Bray, T., and A. Layman, "Namespaces in XML", W3C REC
W3C REC REC-xml-names-19990114, January 1999. REC-xml-names-19990114, January 1999.
[23] Burger, E (Ed.), "A Mechanism for Content Indirection in [23] Burger, E (Ed.), "A Mechanism for Content Indirection in
Session Initiation Protocol (SIP) Messages", RFC 4483, May [24] Gurbani, V., Lawrence, S., and B. Laboratories, "Domain Certificates in
2006 the Session Initiation Protocol (SIP)", draft-ietf-sip-domain-certs-00
(work in progress), November 2007.
[24] Gurbani, V., Lawrence, S., and B. Laboratories, "Domain
Certificates in the Session Initiation Protocol (SIP)", draft-
ietf-sip-domain-certs-00 (work in progress), November 2007.
Author's Addresses Author's Addresses
Reinaldo Penno (Editor) Adam Uzelac
Global Crossing
Rochester, NY - USA
Email: adam.uzelac@globalcrossing.com
Reinaldo Penno
Juniper Networks Juniper Networks
1194 N Mathilda Avenue Sunnyvale, CA - USA
Sunnyvale, CA
USA
Email: rpenno@juniper.net Email: rpenno@juniper.net
Mike Hammer Mike Hammer
Cisco Systems Cisco Systems
13615 Dulles Technology Drive Herndon, VA - USA
Herndon, VA 20171
USA
Email: mhammer@cisco.com Email: mhammer@cisco.com
Sohel Khan, Ph.D. Sohel Khan, Ph.D.
Comcast Cable Communications Comcast Cable Communications
U.S.A USA
Email: sohel_khan@cable.comcast.com Email: sohel_khan@cable.comcast.com
Daryl Malas Daryl Malas
CableLabs CableLabs
858 Coal Creek Circle Louisville, CO - USA
Louisville, CO 80027
Email: d.malas@cablelabs.com Email: d.malas@cablelabs.com
Adam Uzelac
Global Crossing
1120 Pittsford Victor Road
PITTSFORD, NY 14534
USA
Email: adam.uzelac@globalcrossing.com
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