One document matched: draft-ietf-speermint-architecture-05.txt

Differences from draft-ietf-speermint-architecture-04.txt


Speermint Working Group                                        R. Penno 
Internet Draft                                         Juniper Networks 
Intended status: Informational                                 D. Malas  
Expires: August 2008                                            Level 3 
                                                                S. Khan  
                                                                Comcast 
                                                              A. Uzelac  
                                                        Global Crossing 
                                                      February 24, 2008 
                                      
                      SPEERMINT Peering Architecture 
                   draft-ietf-speermint-architecture-05 


Status of this Memo 

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   This Internet-Draft will expire on January 2008. 

Copyright Notice 

   Copyright (C) The IETF Trust (2008). 

Abstract 

   This document defines the SPEERMINT peering architecture, its  
   functional components and peering interface functions. It also 
  describes the steps taken to establish a session between two peering   
 
 
 
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  domains in the context of the functions defined.    
 

Conventions used in this document 

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 
   document are to be interpreted as described in RFC 2119[1] 

Table of Contents 

    
   1. Introduction...................................................3 
   2. Network Context................................................4 
   3. Procedures.....................................................5 
   4. Reference SPEERMINT Architecture...............................6 
   5. Peer Function Examples.........................................8 
      5.1. The Location Function (LF) of an Initiating Provider......8 
         5.1.1. Target address analysis..............................8 
         5.1.2. User ENUM Lookup.....................................9 
         5.1.3. Carrier ENUM lookup.................................10 
         5.1.4. Routing Table.......................................10 
         5.1.5. SIP DNS Resolution..................................10 
         5.1.6. SIP Redirect Server.................................11 
      5.2. The Location Function (LF) of a Receiving Provider.......11 
         5.2.1. Publish ENUM records................................11 
         5.2.2. Publish SIP DNS records.............................11 
         5.2.3. Subscribe Notify....................................11 
      5.3. Signaling Function (SF)..................................11 
      5.4. The Signaling Function (SF) of an Initiating Provider....12 
         5.4.1. Setup TLS connection................................12 
         5.4.2. IPSec...............................................12 
         5.4.3. Co-Location.........................................12 
         5.4.4. Send the SIP request................................12 
      5.5. The Signaling Function (SF) of an Initiating Provider....14 
         5.5.1. Verify TLS connection...............................14 
         5.5.2. Receive SIP requests................................14 
      5.6. Media Function (MF)......................................15 
      5.7. Policy Considerations....................................15 
   6. Call Control and Media Control Deployment Options.............16 
   7. Address space considerations..................................17 
   8. Security Considerations.......................................17 
   9. IANA Considerations...........................................18 
   10. Acknowledgments..............................................18 
   11. References...................................................19 
      11.1. Normative References....................................19 

 
 
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      11.2. Informative References..................................20 
   Author's Addresses...............................................21 
   Intellectual Property Statement..................................21 
   Disclaimer of Validity...........................................22 
    
    

1. Introduction    

   The objective of this document is to define a reference peering 
   architecture in the context of Session PEERing for Multimedia 
   INTerconnect (SPEERMINT). In this process, we define the peering 
   reference architecture (reference, for short), it's functional 
   components, and peering interface functions from the perspective of 
   a SIP [3] Service provider's (SSP) network.   

   This architecture allows the interconnection of two SSPs in layer 5 
   peering as defined in the SPEERMINT Requirements [13] and 
   Terminology [12] documents. 

   Layer 3 peering is outside the scope of this document. Hence, the 
   figures in this document do not show routers so that the focus is on 
   Layer 5 protocol aspects.   

   This document uses terminology defined in the SPEERMINT Terminology 
   document [12], so the reader should be familiar with all the terms 
   defined there.                         




















 
 
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2. Network Context  

   Figure 1 shows an example network context. Two SSPs can form a Layer 
   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 
   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  

   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        |  
                           |     Peering       |  
                           |     Function      |  
                           |                   |                            
                           +-------------------+                              
                                    |  
                                  -----  
      +-----------+              /     \              +-----------+  
      |Enterprise |            --       --            |Enterprise |  
      |Provider A |-----------/           \-----------|Provider B |  
      +-----------+         --             --         +-----------+  
                           /      Public     \  
 
 
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                           |     Internet    |  
                           \     (Layer 3)   /  
      +-----------+         --             --         +-----------+  
      |Service    |-----------\           /-----------|Service    |  
      |Provider C |            --       --            |Provider 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. Procedures  

    

   This document assumes that a call from a UAC end user in the 
   initiating peer's network goes through the following steps to 
   establish a call to a UAS in the receiving peer's network:   

     1. The analysis of a target address.   

    

          a.  If the target address represents an intra-SSP resource, 
             we go directly to step 4.  

 
 
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     2. the discovery of the receiving peering point address,  

     3. the enforcement of authentication and potentially other 
        policies,  

     4. the discovery of the UAS,   

     5. the routing of SIP messages,  

     6. the session establishment,   

     7. the transfer of media which could include voice, video, text 
        and others,  

     8. and the session termination.   

 
4. Reference SPEERMINT Architecture  

   Figure 2 depicts the SPEERMINT architecture and logical functions 
   that form the peering between two SSPs.  


























 
 
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                                +------+ 
                                | DNS, | 
                    +---------->| Db,  |<---------+ 
                    |           | etc  |          | 
                    |           +------+          | 
                    |                             | 
              ------|--------              -------|------- 
             /      v        \            /       v       \ 
            |    +--LUF-+     |          |     +--LUF-+    | 
            |    |      |     |          |     |      |    | 
            |    |      |     |          |     |      |    | 
            |    |      |     |          |     |      |    | 
            |    +------+     |          |     +------+    | 
            |       |         |          |        |        | 
            |       |         |          |        |        | 
            |       v         |          |        v        | 
            |    +--LRF-+     |          |     +--LRF-+    | 
            |    |      |     |          |     |      |    | 
            |    |      |     |          |     |      |    | 
            |    |      |     |          |     |      |    | 
            |    +------+     |          |     +------+    | 
            |      \          |          |          /      | 
            |       `.        |          |         /       | 
            |         \       |          |       .'        | 
            |          `. +---SF--+  +---SF--+  /          | 
            |            \|       |  |       | /           | 
            |             |  SBE  |  |  SBE  |             | 
            | Originating |       |  |       |  Target     | 
            |             +---SF--+  +---SF--+             | 
            |    SSP          |          |       SSP       | 
            |             +---MF--+  +---MF--+             | 
            |             |       |  |       |             | 
            |             |  DBE  |  |  DBE  |             | 
            |             |       |  |       |             | 
            |             +---MF--+  +---MF--+             | 
             \               /            \               / 
              ---------------              --------------- 
                Figure 2: Reference SPEERMINT Architecture 
 
   The procedures presented in Chapter 3 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.   

 
 
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   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 SED required to route the request to that 
   domain.  

   Location Function (LF): The Location functions is composed of the 
   LUF and LRF functions  

   Signaling Function (SF): Purpose is to perform 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).  

   Media Function (MF): Purpose is to perform media related function 
   such as media transcoding and media security implementation between 
   two SIP providers.  

   The intention of defining these functions is to provide a framework 
   for design segmentation and allow each one to evolve independently.  

 
5. Peer Function Examples  

   This section describes the functions in more detail and provides 
   some examples on the role they would play in a SIP call in a Layer 5 
   peering scenario.  

   Some of the information in the chapter is taken from [14] and is put 
   here for continuity purposes. 

5.1. The Location Function (LF) of an Initiating Provider  

 
   Purpose is to determine the SF of the target domain of a given 
   request and optionally develop Session Establishment Data (SED) 
   [12]. The LF of an Initiating SSP analyzes target address and 
   discovers the next hop signaling function (SF) in a peering 
   relationship using the Look-Up Function. The resource to determine 
   the SF of the target domain might be provided by a third-party as in 
   the assisted-peering case. 

 
5.1.1. Target address analysis  

 

 
 
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   When the initiating SSP receives a request to communicate, it 
   analyzes the target state data to determine whether the call needs 
   to be terminated internal or external to its network. The analysis 
   method is internal to the SSP; thus, outside the scope of SPEERMINT. 
   Note that the SSP is free to consult any manner of private data 
   sources to make this determination.  

   If the target address does not represent a resource inside the 
   initiating SSP's administrative domain or federation of domains, the 
   initiating SSP resolves the call routing data by using the Location 
   Function (LF).  

   If the request to communicate is for an im: or pres: URI type, the 
   initiating peer follows the procedures in [8].  If the highest 
   priority supported URI scheme is sip: or sips:, the initiating peer 
   skips to SIP DNS resolution in Section 5.1.5. Likewise, if the 
   target address is already a sip: or sips: URI in an external domain, 
   the initiating peer skips to SIP DNS resolution in Section 5.1.5.   

   If the target address corresponds to a specific E.164 address, the 
   peer may need to perform some form of number plan mapping according 
   to local policy.  For example, in the United States, a dial string 
   beginning "011 44" could be converted to "+44", or in the United 
   Kingdom "00 1" could be converted to "+1".  Once the peer has an 
   E.164 address, it can use ENUM.  

 
5.1.2. User ENUM Lookup  

   If an external E.164 address is the target, the initiating peer 
   consults the public "User ENUM" rooted at e164.arpa, according to 
   the procedures described in RFC 3761.  The peer MUST query for the 
   "E2U+sip" enumservice as described in RFC 3764 [11], but MAY check 
   for other enumservices.  The initiating peer MAY consult a cache or 
   alternate representation of the ENUM data rather than actual DNS 
   queries.  Also, the peer MAY skip actual DNS queries if the 
   initiating peer is sure that the target address country code is not 
   represented in e164.arpa.  If a sip: or sips: URI is chosen the peer 
   skips to Section 5.1.5.  

   If an im: or pres: URI is chosen for based on an "E2U+im" [10] or 
   "E2U+pres" [9] enumserver, the peer follows the procedures for 
   resolving these URIs to URIs for specific protocols such a SIP or 
   XMPP as described in the previous section.  

 

 
 
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5.1.3. Infrastructure ENUM lookup  

   Next the initiating peer checks for a carrier-of-record in a carrier 
   ENUM domain according to the procedures described in [12].  As in 
   the previous step, the peer MAY consult a cache or alternate 
   representation of the ENUM data in lieu of actual DNS queries.  The 
   peer 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 peer skips to Section 
   5.1.5, otherwise the peer continues processing according to the next 
   section. 

5.1.4. Routing Table  

   If there is no user ENUM records and the initiating peer cannot 
   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 rewrites the Request-URI to address the 
   gateway 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.  

 
5.1.5. SIP DNS Resolution  

   Once a sip: or sips: in an external domain is selected as the 
   target, the initiating peer MAY apply local policy to decide whether 
   forwarding requests to the target domain is acceptable.  If so, the 
   initiating peer uses the procedures in RFC 3263 [4] Section 4 to 
   determine how to contact the receiving peer.  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. 

   When communicating with a public external peer, entities compliant 
   to this document MUST only select a TLS-protected transport for 
   communication from the initiating peer to the receiving peer.  Note 
   that this is a single-hop requirement.  Either peer MAY insist on 
   using a sips: URI which asserts that each hop is TLS-protected, but 
   this document does not require protection over each hop. 

 
 
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5.1.6. SIP Redirect Server    

   A SIP Redirect Server may help in resolving the current address of a 
   UAS.  

 
5.2. The Location Function (LF) of a Receiving Provider  

5.2.1. Publish ENUM records  

   The receiving peer SHOULD participate by publishing "E2U+sip" and 
   "E2U+pstn" records with sip: or sips: URIs wherever a public carrier 
   ENUM root is available.  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.  

5.2.2. Publish SIP DNS records  

   To receive peer requests, the receiving peer MUST insure that it   
   publishes appropriate NAPTR, SRV, and address (A and/or AAAA) 
   records in the LF relevant to the peer's SF.    

5.2.3. Subscribe Notify   

   Policies function may also be optionally implemented by dynamic 
   subscribe, notify, and exchange of policy information and feature 
   information among SSPs [22].   

5.3. Signaling Function (SF)  

   The purpose of signaling function is to perform routing of SIP 
   messages, to optionally perform termination and re-initiation of a 
   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 signaling function perform the routing of SIP messages. The 
   optional termination and re-initiation of calls are performed by the 
   signaling path border element (SBE).   

   Optionally, a SF may perform additional functions such as Session 
   Admission Control, SIP Denial of Service protection, SIP Topology 
   Hiding, SIP header normalization, and SIP security, privacy and 
   encryption.  

 
 
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   The SF can also process SDP payloads for media information such as 
   media type, bandwidth, and type of codec; then, communicate this 
   information to the media function. Signaling function may optionally 
   communicate with the network to pass Layer 3 related policies [10]  

 
5.4. The Signaling Function (SF) of an Initiating Provider  

5.4.1. Setup TLS connection 

   Once a transport, port, and address are found, the initiating SSP 
   will open or find a reusable TLS connection to the peer.  The 
   initiating provider MUST verify the server certificate that SHOULD 
   be rooted in a well-known certificate authority.  The initiating SSP 
   MUST be prepared to provide a TLS client certificate upon request 
   during the TLS handshake.  The client certificate MUST contain a DNS 
   or URI choice type in the subjectAltName which corresponds to the 
   domain asserted in the host production of the From header URI.  The 
   certificate SHOULD be valid and rooted in a well-known certificate 
   authority. 

   Note that the client certificate MAY contain a list of entries in 
   the subjectAltName, only one of which has to match the domain in the 
   From header URI. 

5.4.2. IPSec  

   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. 
    
5.4.3. Co-Location   

   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. 
 
5.4.4. Send the SIP request 

   Once a TLS connection between the peers is established, the 
   initiating peer sends the request.  When sending some requests, the 


 
 
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   initiating peer MUST verify and assert the senders identity using 
   the SIP Identity mechanism.  

   The domain name in the URI of the From: header MUST be a domain 
   which was present in the certificate provided when establishing the 
   TLS connection for this request, even if the user part has an 
   anonymous value.  If the From header contains the user URI parameter 
   with the value of "phone", the user part of the From header URI MUST 
   be a complete and valid tel: URI [9] telephone-subscriber 
   production, and SHOULD be a global-number.  For example, the 
   following are all acceptable and the first three are encouraged: 

      From: "John Doe" john.doe@example.net 

      From: "+12125551212" <+12125551212@example.net;user=phone> 

      From: "Anonymous" <anonymous@example.net> 

      From: <4092;phone-context=+12125554000@example.net;user=phone> 

      From: "5551212" <5551212@example.net> 

      The following are not acceptable: 

      From: "2125551212" <2125551212@example.net;user=phone> 

      From: "Anonymous" <anonymous@anonymous.invalid> 

   In addition, new requests MUST 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 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. 

   The initiating peer MAY include any SIP option-tags in Supported, 
   Require, or Proxy-Require headers according to procedures in 
   standards-track SIP extensions.  Note however that the initiating 
   peer MUST be prepared to fallback to baseline SIP functionality as 
   defined by the mandatory-to-implement features of RFC 3261, RFC 
   3263,and RFC 3264 [7], except that peers implementing this 
   specification MUST implement SIP over TLS using the sip: URI scheme, 
   the SIP Identity header, and RFC 4320 [10] non-INVITE transaction 
   fixes. 


 
 
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5.5. The Signaling Function (SF) of an Target Provider  

 
5.5.1. Verify TLS connection 

   When the receiving peer receives a TLS client hello, it responds 
   with its certificate.  The receiving peer certificate SHOULD be 
   valid and rooted in a well-known certificate authority.  The 
   receiving peer MUST request and verify the client certificate during 
   the TLS handshake.  

   Once the initiating peer has been authenticated, the receiving peer 
   can authorize communication from this peer based on the domain name 
   of the peer and the root of its certificate.  This allows two 
   authorization models to be used, together or separately.  In the 
   domain-based model, the receiving peer can allow communication from 
   peers with some trusted administrative domains that use general- 
   purpose certificate authorities, without explicitly permitting all 
   domains with certificates rooted in the same authority.  It also 
   allows a certificate authority (CA) based model where every domain 
   with a valid certificate rooted in some list of CAs is automatically 
   authorized. 

 
5.5.2. Receive SIP requests 

   Once a TLS connection is established, the receiving peer is prepared 
   to receive incoming SIP requests.  For new requests (dialog forming 
   or not) the receiving peer verifies that the target (request-URI) is 
   a domain that for which it is responsible. For these requests, there 
   should be no remaining Route header field values. Next the receiving 
   verifies that the Identity header is valid, corresponds to the 
   message, and 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. 

   For in-dialog requests, the receiving peer can verify that it 
   corresponds to the top-most Route header field value.  The peer also 
   validates any Identity header if present. 

   The receiving peer MAY reject incoming requests due to local policy. 
   When a request is rejected because the initiating peer is not 
   authorized to peer, the receiving peer SHOULD respond with a 403 
   response with the reason phrase "Unsupported Peer". 

 
 
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5.6. Media Function (MF)  

   The purpose of the MF is to perform media related functions such as 
   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) to another (e.g., EvRC).  Additionally, the MF MAY 
   perform media relaying, media security, privacy, and encryption.  

5.7. Policy 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 Peer dependent or independent, creating the 
   following peering policy tree definition:   

 
     o  Peer Independent                                          
        Session dependent                                         
        Session independent   



 
 
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     o  Peer Dependent                                           
        Session dependent                                        
        Session independent   

    

6. Call Control and Media Control Deployment Options  

   The peering functions can either be deployed along the following two 
   dimensions depending upon how the signaling function and the media 
   function along with IP functions 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 peering points 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 
 
 
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   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 peering proxies. 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 address space, which is defined by 
   the federation, which may be entirely on the public Internet, or 
   some private address space. The origination or termination networks 
   may or may not entirely be in that same address space.  If they are 
   not, then a network address translation (NAT) or similar may be 
   needed before the signaling or media is presented correctly to the 
   federation. The only requirement is that all associated entities 
   across the peering interface are reachable.  

 
8. Security Considerations  

 
   In all cases, cryptographic-based security should be maintained as 
   an optional requirement between peering providers conditioned on the 
   presence or absence of underlying physical security of peer 
   connections, e.g. within the same secure 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.  

 
 
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   TODO:  Address RFC-3552 BCP items.    

9. IANA Considerations  

 
   There are no IANA considerations at this time.  
 
10. Acknowledgments  

   The working group thanks Sohel Khan for his initial architecture  
   draft that helped to initiate work on this draft.  
 
   A significant portion of this draft is taken from [14] with  
   permission from the author R. Mahy. The other important contributor  
   is Otmar Lendl.  































 
 
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11. References 

11.1. Normative References 

   [1]   Bradner, S., "Key words for use in RFCs to Indicate 
         Requirement Levels", BCP 14, RFC 2119, March 1997.  

   [2]   Mealling, M. and R. Daniel, "The Naming Authority Pointer 
         (NAPTR) DNS Resource Record", RFC 2915, September 2000.  

   [3]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., 
         Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: 
         Session Initiation Protocol", RFC 3261, June 2002.  

   [4]   Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol 
         (SIP): Locating SIP Servers", RFC 3263, June 2002.  

   [5]   Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., and 
         T. Wright, "Transport Layer Security (TLS) Extensions", RFC 
         4366, April 2006.  

   [6]   Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, 
         "RTP: A Transport Protocol for Real-Time Applications", STD 
         64, RFC 3550, July 2003.  

   [7]   Peterson, J., Liu, H., Yu, J., and B. Campbell, "Using E.164 
         numbers with the Session Initiation Protocol (SIP)", RFC 3824, 
         June 2004.  

   [8]   Peterson, J., "Address Resolution for Instant Messaging and 
         Presence",RFC 3861, August 2004.   

   [9]   Peterson, J., "Telephone Number Mapping (ENUM) Service 
         Registration for Presence Services", RFC 3953, January 2005.  

   [10]  ETSI TS 102 333: " Telecommunications and Internet converged 
         Services and Protocols for Advanced Networking (TISPAN); Gate 
         control protocol".  

   [11]  Peterson, J., "enumservice registration for Session Initiation 
         Protocol (SIP) Addresses-of-Record", RFC 3764, April 2004.  

   [12]  Livingood, J. and R. Shockey, "IANA Registration for an          
         Enumservice Containing PSTN Signaling Information", RFC 4769, 
         November 2006.  


 
 
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11.2. Informative References 

   [13]  Malas, D., "SPEERMINT Terminology", draft-ietf-speermint-
         terminology-16 (work in progress), February 2008.  

   [14]  Mule, J-F., "SPEERMINT Requirements for SIP-based VoIP 
         Interconnection", draft-ietf-speermint-requirements-03.txt, 
         November 2007.  

   [15]  Mahy, R., "A Minimalist Approach to Direct Peering", draft-         
         mahy-speermint-direct-peering-02.txt, July 2007.  

   [16]  Penno, R., et al., "SPEERMINT Routing Architecture Message          
         Flows", draft-ietf-speermint-flows-02.txt", April 2007.  

   [17]  Houri, A., et al., "RTC Provisioning Requirements", draft-         
         houri-speermint-rtc-provisioning-reqs-00.txt, June, 2006.  

   [18]  Habler, M., et al., "A Federation based VOIP Peering         
         Architecture", draft-lendl-speermint-federations-03.txt,          
         September 2006.  

   [19]  Mahy, R., "A Telephone Number Mapping (ENUM) Service          
         Registration for Instant Messaging (IM) Services", RFC 5028         

   [20]  Haberler, M. and R. Stastny, "Combined User and Carrier ENUM 
         in the e164.arpa tree", draft-haberler-carrier-enum-03 (work 
         in progress), March 2006.  

   [21]  Penno, R., Malas D., and Melampy, P., "A Session Initiation          
         Protocol (SIP) Event package for Peering", draft-penno-
         sipping-peering-package-01 (work in progress), September 2006.  

   [22]  Hollander, D., Bray, T., and A. Layman, "Namespaces in XML",          
         W3C REC REC-xml-names-19990114, January 1999.  

   [23]  Burger, E (Ed.), "A Mechanism for Content Indirection in          
         Session Initiation Protocol (SIP) Messages", RFC 4483, May 
         2006  








 
 
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Author's Addresses 

    
   Mike Hammer  
   Cisco Systems  
   13615 Dulles Technology Drive  
   Herndon, VA 20171  
   USA  
   Email: mhammer@cisco.com   
        
   Sohel Khan, Ph.D.  
   Comcast Cable Communications   
   U.S.A  
   Email: sohel_khan@cable.comcast.com  
        
   Daryl Malas  
   Level 3 Communications LLC  
   1025 Eldorado Blvd.  
   Broomfield, CO 80021  
   USA     
   EMail: daryl.malas@level3.com  
        
   Reinaldo Penno (Editor)  
   Juniper Networks  
   1194 N Mathilda Avenue  
   Sunnyvale, CA  
   USA  
   Email: rpenno@juniper.net  
        
   Adam Uzelac  
   Global Crossing  
   1120 Pittsford Victor Road  
   PITTSFORD, NY 14534  
   USA  
   Email: adam.uzelac@globalcrossing.com  
    

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