[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 RFC 6405

SPEERMING Working Group                                   A. Uzelac, Ed.
Internet-Draft                                           Global Crossing
Intended status: Informational                               Y. Lee, Ed.
Expires: October 12, 2008                                  Comcast Cable
                                                          April 10, 2008


                       VoIP SIP Peering Use Cases
           draft-ietf-speermint-voip-consolidated-usecases-06

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on October 12, 2008.

Abstract

   This document depicts many common VoIP use case for SIP Peering.
   These use cases are categorized into static and on-demand, and then
   further sub-categorized into direct and indirect.  These use cases
   are not an exhaustive set, but rather the most common use cases
   deployed today.  This document captures them to provide a reference.









Uzelac & Lee            Expires October 12, 2008                [Page 1]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3

   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3

   3.  Reference Architecture . . . . . . . . . . . . . . . . . . . .  3

   4.  Contexts of Use Cases  . . . . . . . . . . . . . . . . . . . .  4

   5.  User Cases . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     5.1.  Static Peering Use Cases . . . . . . . . . . . . . . . . .  6
       5.1.1.  Static Direct Peering Use Case . . . . . . . . . . . .  6
       5.1.2.  Static Direct Peering Use Case - Assisted LUF and
               LRF  . . . . . . . . . . . . . . . . . . . . . . . . . 11
       5.1.3.  Static Indirect Peering Use Case . . . . . . . . . . . 13
       5.1.4.  Static Indirect Peering Use Case - Assisted LUF
               and LRF  . . . . . . . . . . . . . . . . . . . . . . . 19
     5.2.  On-demand Peering Use Cases  . . . . . . . . . . . . . . . 20
       5.2.1.  On-demand Direct Peering Use Case  . . . . . . . . . . 20

   6.  Federations  . . . . . . . . . . . . . . . . . . . . . . . . . 21
     6.1.  Federation Examples  . . . . . . . . . . . . . . . . . . . 21
       6.1.1.  Trivial Federations  . . . . . . . . . . . . . . . . . 21
       6.1.2.  Access List based Federations  . . . . . . . . . . . . 22
       6.1.3.  Central SIP Proxy Federations  . . . . . . . . . . . . 22
       6.1.4.  Architecture, scalability and business scalability . . 22

   7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 22

   8.  Security and Privacy Considerations  . . . . . . . . . . . . . 23

   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 23

   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 23
     10.2. Informative References . . . . . . . . . . . . . . . . . . 24

   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25
   Intellectual Property and Copyright Statements . . . . . . . . . . 26











Uzelac & Lee            Expires October 12, 2008                [Page 2]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


1.  Introduction

   This document attempts to capture VoIP use cases for Session
   Initiation Protocol (SIP) [RFC3261] based peering.  These use cases
   will assist in identifying requirements and future works for VoIP
   Peering using SIP.

   Only use cases related to VoIP are considered in this document.
   Other real-time SIP communications use cases, like Instant Messaging
   (IM) and presence are out of scope for this document.  In describing
   use cases, the intent is descriptive, not prescriptive.

   There are existing documents [I-D.lee-speermint-use-case-cable],
   [I-D.lendl-speermint-federations],
   [I-D.mahy-speermint-direct-peering],
   [I-D.schwartz-speermint-use-cases-federations], and
   [I-D.uzelac-speermint-use-cases] that have captured use case
   scenarios.  This draft draws from those documents.  The use cases
   contained in this document attempts to be as comprehensive as
   possible, but should not be considered the exclusive set of use
   cases.


2.  Terminology

   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 [RFC2119].


3.  Reference Architecture

   The diagram below provides the reader with a context for the VoIP use
   cases in this draft.

















Uzelac & Lee            Expires October 12, 2008                [Page 3]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


    +-------------------+-------------------------+-------------------+
    |                   | LUF/LRF Provider Domain |                   |
    |                   |   Indirect SSP Domain   |                   |
    |                   |                         |                   |
    |                   |    +------+ +------+    |                   |
    |                   |    +A-LUF + + A-LRF|    |                   |
    |                   |    +------+ +------+    |                   |
    |                   |                         |                   |
    |                   |    +------+ +------+    |                   |
    |                   |    | I-SBE| | I-DBE|    |                   |
    |                   \    +------+ +------+    /                   |
    |           +------+ \                       / +------+           |
    |     +-----+O-LUF |  \                     /  |T-LUF +-----+     |
    |     |     +O-LRF |   \                   /   |T-LRF +     |     |
    |     |     +------+    \                 /    +------+     |     |
    |     |                  \               /                  |     |
    |     |     +------+      \             /      +------+     |     |
    |     |     | O-SBE|       \           /       | T-SBE|     |     |
    |     |     +---+--+        \         /        +---+--+     |     |
    |     |         |            \       /             |        |     |
    |     |         |             \     /              |        |     |
    |     |     +---+---+          \   /           +---+---+    |     |
    |     +-----+O-Proxy|           \ /            |T-Proxy+--- +     |
    |           +-----+-+            +             +-+-----+          |
    |   +----+        |              |               |        +----+  |
    |   |UAC +--------+              |               +--------+ UAS|  |
    |   +----+        +------+       |       +------+         +----+  |
    |                 | O-DBE|       |       | T-DBE|                 |
    |                 +------+       |       +------+                 |
    |                                |                                |
    |     Originating SSP Domain     |       Terminating SSP Domain   |
    +-----------------------------------------------------------------+


                             General Overview

                                 Figure 1

   PLEASE NOTE: In Figure 1 - the elements defined are optional in many
   use cases.


4.  Contexts of Use Cases

   Use cases are sorted into two general groupings: Static and On-demand
   Peering [I-D.ietf-speermint-terminology].  Each grouping can be
   further sub-divided to Direct Peering and Indirect Peering
   [I-D.ietf-speermint-terminology].  Though there may be some overlap



Uzelac & Lee            Expires October 12, 2008                [Page 4]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


   among the use cases in these categories, there are different
   requirements between the scenarios.  Each use-case must specify a
   basic set of required operations to be performed by each member when
   peering.

   These can include:

   o  Peer Discovery - Peer discovery via a Look-up function (LUF) to
      determine the administrative domain of the target.

   o  Location Determination - A location determination process serves
      to create the Session Establishment Data (SED).  Examples: Public
      User-ENUM, public Infrastructure ENUM, private ENUM tree, SIP
      Redirect, DUNDi.

   o  Next Hop Determination - A next hop determination based on the SED
      is then completed.  If a location function query did not return an
      URI of the form sip:user@IP-address, then the originating SSP has
      to translate the domain part of the URI to an IP-address (plus
      perhaps fall-backs) in order to contact the next hop.  Examples:
      [RFC3263] in the public DNS.  RFC3263 in a federation private DNS.
      RFC3263 in the public DNS with split-DNS, P2P SIP, modified
      [RFC3263] in the public DNS (e.g. a federation-specific prefix to
      the domain name).

   o  Call setup - SSPs that are interconnecting to one another may also
      define specifics on what SIP features need to be used when
      contacting the next hop in order to a) reach the next hop at all
      and b) to prove that the sender is a legitimate peering partner.

      Examples: hard-code transport (TCP/UDP/TLS), non-standard port
      number, specific source IP address (e.g. in a private L3 network),
      which TLS client certificate [RFC3546] to use, and other
      authentication schemes.

   o  Call reception - This step serves to ensure that the type of
      relationship (static or on-demand, indirect or direct) is
      understood and acceptable.  For instance, the receiving side
      border elements need to determine whether the INVITE it just
      received really came from a member of the federation, possibly via
      an access control list entry.  This is the flip side of step four.
      Example: verify TLS certificate [RFC3546] check incoming
      interface/VLAN,check source IP address against a configured list
      of valid ones.







Uzelac & Lee            Expires October 12, 2008                [Page 5]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


5.  User Cases

   Please note there are intra-domain message flows within the use cases
   to serve as supporting background information.  Only inter-domain
   communications are germane to Speermint.

5.1.  Static Peering Use Cases

   Static Peering [I-D.ietf-speermint-terminology] describes the use
   case when two SSPs form a peering relationship with some form of
   association established prior to the exchange of traffic.  Pre-
   association is a prerequisite to static peering.  Static peering is
   used in cases when two peers want a consistent and tightly controlled
   approach to peering.  In this scenario, a number of variables, such
   as remote proxy IP address and QoS parameters, can be defined upfront
   and known by each SSP prior to peering.

5.1.1.  Static Direct Peering Use Case

   This is the simplest form of a peering use case.  Two SSPs negotiate
   and agree to establish a SIP peering relationship.  The peer
   connection is statically configured and is direct between the
   connected SSPs.  The peers may exchange interconnection parameters
   such as DSCP policies, subscriber SIP-URI and proxy location prior to
   establishing the interconnection.  Typically, they only accept
   traffic originating directly from the trusted peer.

























Uzelac & Lee            Expires October 12, 2008                [Page 6]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


         +--------------------+             +---------------------+
         |        O-SSP       |             |        T-SSP        |
         |       +-----+      |             |       +-----+       |
         |       |O-LUF|      |             |       |T-LUF|       |
         |       |O-LRF|      |             |      /|T-LRF|       |
         |      /+-----+\     |             |     / +-----+       |
         |  (2,3,4)     (6)   |             |    /                |
         |    /           \   |             |   /(8,9)            |
         |+-------+     +-----+             +-----+      +-------+|
         ||O-Proxy|-(5)-|O-SBE+-----(7)-----+T-SBE|-(10)-|T-Proxy||
         |+-------+     +-----+             +-----+      +-------+|
         |    |               |             |                |    |
         |   (1)              |             |               (11)  |
         |    |               |             |                |    |
         | +-----+            |             |             +-----+ |
         | | UAC +============+=====(12)====+=============+ UAS | |
         | +-----+            |             |             +-----+ |
         +--------------------+             +---------------------+
              example.com                         example.net


                      Static Direct Peering Use Case

                                 Figure 2

   The following is a high-level depiction of the use case:

   1.   UAC initiates a call via SIP INVITE to O-Proxy.  O-Proxy is the
        home proxy for UAC.

         INVITE sip:+19172223333@example.net;user=phone SIP/2.0
         Via: SIP/2.0/TCP client.example.com:5060
           ;branch=z9hG4bK74bf9
         Max-Forwards: 10
         From: Alice <sip:+14083332222@example.com;user=phone>
           ;tag=12345
         To: Bob sip+19172223333@example.net;user=phone
         Call-ID: abcde@client.example.com
         CSeq: 1 INVITE
         Contact: <sip:+19172223333@client.example.com;user=phone
           ;transport=tcp>
         Content-Type: application/sdp

   2.   O-Proxy checks the domain of the R-URI and discovers that the
        UAS's domain is external.  So, it queries LUF for SED
        information from a routing database.  In this example, the LUF
        is an ENUM database.  The ENUM entry looks similar to this:




Uzelac & Lee            Expires October 12, 2008                [Page 7]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


          $ORIGIN 3.3.3.3.2.2.2.7.1.9.example.net
          NATPTR 10 100 "u" "E2U+SIP"
           "!^.* !sip:\\1@t-sbe.example.net!"

        This SED data can be inputted by O-SSP or populated by the T-SSP

   3.   Routing database entity replies with SED to called party.  In
        this example, the SED is DNS NAPTR record.  The LRF does a DNS
        lookup of the domain name of the NAPTR record and receives a
        response similar to this:

       ;;       order perf flags service    regxp replacement
       IN NAPTR 50    50   "S"   "SIPS+D2T" ""    _sip._tcp.t-sbe.example.net
       IN NAPTR 90    50   "S"   "SIPS+D2U" ""    _sip._udp.t-sbe.example.net

   4.   O-Proxy decides to use TCP for transport protocol, so it sends a
        DNS query for the SRV record for "_sip._tcp.t-sbe.example.net".

        ;;     priority  weight   port  target
        IN SRV 0         1        5060  t-sbe1.example.net
        IN SRV 0         2        5060  t-sbe2.example.net

   5.   Given the O-Proxy's internal routing policy, O-Proxy decides to
        use O-SBE to reach T-SBE, so it routes the INVITE request to
        O-SBE and adds the route header pointing to T-SBE in the INVITE
        request.

         INVITE sip:+19172223333@example.net;user=phone SIP/2.0
         Via: SIP/2.0/TCP o-proxy.example.com:5060
           ;branch=z9hG4bKye8ad
         Via: SIP/2.0/TCP client.example.com:5060
           ;branch=z9hG4bK74bf9;received=192.0.1.1
         Max-Forwards: 9
         Route: <sip:t-sbe1.example.net>
         Record-Route: <sip:o-proxy.example.com;lr>
         From: Alice <sip:+14083332222@example.com;user=phone>
           ;tag=12345
         To: Bob sip+19172223333@example.net;user=phone
         Call-ID: abcde@client.example.com
         CSeq: 1 INVITE
         Contact: <sip:+19172223333@client.example.com;user=phone
           ;transport=tcp>
         Content-Type: application/sdp

   6.   O-SBE receives the request and pops the top entry of the Route
        header which contains "t-sbe1.example.net".  O-SBE sends a DNS
        query for "t-sbe1.example.net" to get the A-Record:




Uzelac & Lee            Expires October 12, 2008                [Page 8]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


          ;; DNS ANSWER
          t-sbe1.example.net   A   192.2.0.100
          t-sbe1.example.net   A   192.2.0.101

   7.   O-SBE sends the INVITE to T-SBE.  O-SBE is the entry point to
        the O-SSP domain, so it should ensure subsequent mid-dialog
        requests traverse via itself.  If O-SBE chooses to act as B2BUA
        , it will terminate the call and generate a new back-to-back
        INVITE request.  If O-SBC chooses to act as proxy, it should
        record-route to stay in the call path.  In this example, O-SBE
        is a B2BUA.

         INVITE sip:+19172223333@example.net;user=phone SIP/2.0
         Via: SIP/2.0/TCP o-sbe1.example.com:5060
           ;branch= z9hG4bK2d4zzz;
         Max-Forwards: 10
         Record-Route: <sip:o-sbe1.example.com:5060;lr>
         From: Alice <sip:+14083332222@example.com;user=phone>
           ;tag=54321
         To: Bob sip:+19172223333@example.net;user=phone
         Call-ID: abcde-osbe1@o-sbe1.example.com
         CSeq: 1 INVITE
         Contact: <sip:+19172223333@o-sbe1.example.com;user=phone
           transport=tcp>
         Content-Type: application/sdp

   8.   T-SBE determines called party home proxy and directs call to
        called party.  T-SBE may use ENUM or other internal mechanism to
        locate the home proxy.  If T-SSP uses ENUM, this internal ENUM
        entry is different from the external ENUM entry populated for
        O-SSP.  For internal use, it should return the home proxy of
        UAS.  For external use, it should return T-SBE.

         $ORIGIN 3.3.3.3.2.2.2.7.1.9.example.net
         NATPTR 10 100 "u" "E2U+SIP"
           "!^.* !sip:bob@t-proxy.example.net!"

   9.   T-SBE receives the NAPTR record and query DNS for the "home-
        proxy.example.net".  The DNS returns an A-Record:

          ;; DNS ANSWER
          t-proxy.example.net   A   192.2.1.2

   10.  T-SBE is a B2BUA, so it generates a new INVITE and sends it to
        UAS's home proxy:






Uzelac & Lee            Expires October 12, 2008                [Page 9]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


         INVITE sip:+19172223333@example.net;user=phone SIP/2.0
         Via: SIP/2.0/TCP t-sbe1.example.net:5060
           ;branch= z9hG4bK28uyyy;
         Max-Forwards: 10
         Record-Route: <sip:t-sbe1.example.net:5060;lr>
         From: Alice <sip:+14083332222@example.com;user=phone>
           ;tag=54321
         To: Bob sip:+19172223333@example.net;user=phone
         Call-ID: abcde-tsbe1@t-sbe1.example.com
         CSeq: 1 INVITE
         Contact: <sip:+19172223333@o-sbe1.example.com;user=phone
           transport=tcp>
         Content-Type: application/sdp

   11.  Finally, UAS's home proxy forwards the INVITE request to UAS.

         INVITE sip:+19172223333@server.example.net;user=phone SIP/2.0
         Via: SIP/2.0/TCP t-proxy.example.net:5060
           ;branch= z9hG4bK28u111;
         Via: SIP/2.0/TCP t-sbe1.example.net:5060
           ;branch= z9hG4bK28uyyy; received=192.2.0.100
         Max-Forwards: 9
         Record-Route: <sip:t-proxy.example.net:5060;lr>,
           <sip:t-sbe1.example.net:5060;lr>
         From: Alice <sip:+14083332222@example.com;user=phone>
           ;tag=54321
         To: Bob sip:+19172223333@example.net;user=phone
         Call-ID: abcde-tsbe1@t-sbe1.example.com
         CSeq: 1 INVITE
         Contact: <sip:+19172223333@o-sbe1.example.com;user=phone
           transport=tcp>
         Content-Type: application/sdp

   12.  RTP is established between UAC and UAS.

5.1.1.1.  Administrative characteristics

   The static direct peering use case is typically implemented in a
   scenario where exists a strong degree of trust between the two
   administrative domains.  Both administrative domains typically sign a
   peer agreement which state clearly the peering policies and terms.

5.1.1.2.  Options and Nuances

   In Figure 2.  O-SSP and T-SSP peer via SBEs.  Normally, the operator
   will deploy the SBE in the edge of its administrative domain.  The
   signaling traffic will pass between two networks through the SBEs.
   The operator has many reasons to deploy a SBE.  For example, either



Uzelac & Lee            Expires October 12, 2008               [Page 10]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


   proxy and UA may use [RFC1918] addresses that are not routable in the
   target network.  The SBE can perform a NAT function.  Also, the SBE
   eases the operation cost for deploying or removing L5 network
   elements.  Consider the deployment architecture where multiple
   proxies connect to a single SBE.  An operator can add or remove a
   proxy without coordinating with the peer operator.  The peer operator
   "sees" only the SBE.  As long as the SBE is maintained in the path,
   the peer operator does not need to be notified.

   When an operator deploys a SBE, the operator is required to advertise
   the SBE to the peer LRF so that the peer operator can locate the SBE
   and route the traffic to the SBE accordingly.

   SBE deployment is a decision within an administrative domain.  Either
   administrative domain or both administrative domains can decide to
   deploy SBE.  To the peer network, most important is to identify the
   next-hop address.  Whether next-hop is a proxy or SBE, the peer
   network will not see any difference.

5.1.2.  Static Direct Peering Use Case - Assisted LUF and LRF

   This use case shares many properties with the static direct use case.
   There must exist a pre-association between the O-SSP and T-SSP.  The
   difference is O-SSP will use the Assisted Service Provider (A-SP) for
   LUF and LRF.  In other words, LUF/LRF provider stores the SED to
   reach T-SSP and provides to O-SSP when O-SSP queries it.

























Uzelac & Lee            Expires October 12, 2008               [Page 11]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


                            +-----------------+
                            |LUF/LRF Provider |
                            |                 |
                            |     +-------+   |
                            |   +-+ A-LUF |   |
                            |  /  | A-LRF |   |
       +--------------------+ /  ++-------+   +---------------------+
       |       O-SSP        |/  /             |         T-SSP       |
       |       +------------/ (6)             |        +-----+      |
       |      /             | /               |        |T-LUF|      |
       |  (2,3,4)         +--+                |      +-|T-LRF|      |
       |    /            /  |                 |     /  +-----+      |
       |   /            /   |                 |    /(8,9)           |
       |+-------+     +-----+                 +-----+      +-------+|
       ||O-Proxy|-(5)-|O-SBE+-------(7)-------+T-SBE|-(10)-|T-Proxy||
       |+-------+     +-----+                 +-----+      +-------+|
       |    |               |                 |                |    |
       |   (1)              |                 |              (11)   |
       |    |               |                 |                |    |
       | +-----+      +-----+                 +-----+       +-----+ |
       | | UAC +======|0-DBE+=======(12)======+T-DBE+=======+ UAS | |
       | +-----+      +-----+                 +-----+       +-----+ |
       +--------------------+                 +---------------------+
             example.com                            example.net


              Static Direct Peering with Assisted LUF and LRF

                                 Figure 3

   The call flow looks almost identical to Static Direct Peering Use
   Case except Step 2,3 and 4 which happen in A-SP remotely instead of
   happening in O-SSP domain.

   Note that the media passes through O-DBE and T-DBE in the Figure 3.
   This is optional.  A DBE may be needed for transcoding or other
   traffic policy for media.

5.1.2.1.  Administrative Characteristics

   The LUF/LRF providers provides the LUF and LRF services for the
   O-SSP.  As such , LUF/LRF providers, O-SSP and T-SSP form a trusted
   administrative domain.  To reach T-SSP, O-SSP must still require pre-
   arranged assignments for the peer relationship with T-SSP.  L5 policy
   is maintained in the O-SSP and T-SSP domains, and LUF/LRF provider is
   neither unaware nor responsible for L5 policy.

   A LUF/LRF provider can serve multiple administrative domains.  LUF/



Uzelac & Lee            Expires October 12, 2008               [Page 12]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


   LRF provider must not share SED from one administrative domain to
   another administrative domain without appropriate permission granted.

5.1.2.2.  Options and Nuances

   LRF/LRF provider can use multiple methods to provide SED to O-SSP.
   Most commonly used are ENUM query and SIP Redirect.  O-SSP should
   negotiate with LUF/LRF provider which query method it will use prior
   to sending query to LUF/LRF provider.

   T-SSP needs to populate its users' SED to LUF/LRF provider.
   Currently, this procedure is non-standardized and labor intensive.
   IETF is working on this problem and trying to standardize this
   procedure for ENUM.  [I-D.newton-peppermint-problem-statement] and
   [I-D.lewis-peppermint-enum-reg-if] list the problem statements and
   requirements.

5.1.3.  Static Indirect Peering Use Case

   Similar to the Static Direct Peering Use Case, O-SSP and T-SSP has
   pre-arranged assignment for the peer relationship.  The difference
   between Static Direct Use Case and Static Indirect Use Case lies with
   the Layer-5 relationship O-SSP and T-SSP maintain.  In the Indirect
   use case, the O-SSP and T-SSP do not have direct Layer-5
   connectivity.  They require one or multiple Indirect Domains to
   assist routing the SIP messages and possibly the associated media.

5.1.3.1.  Static Indirect Peering Use Case

   Two SSPs negotiate and agree to establish a SIP Peering relation.  In
   this use case for some reason, they don't have direct L5
   connectivity.  The reasons may vary, for example business demands
   and/or domain policy controls.  Due to this indirect relationship the
   signalling will traverse from O-SSP to one or multiple I-SSP(s) to
   reach T-SSP.
















Uzelac & Lee            Expires October 12, 2008               [Page 13]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


      +--------------------+-------------------+---------------------+
      |       O-SSP        |       I-SSP       |         T-SSP       |
      |      +-----+       |                   |        +-----+      |
      |     -+O-LUF|       |                   |        |T-LUF|      |
      |    / |O-LRF+\      |                   |   +----+T-LRF|      |
      |   /  +-----+ \     |                   |  /     +-----+      |
      |  /(2,3,4)     \(6) |                   | /(9,10)             |
      |+-------+     +-----+      +-----+      +-----+      +-------+|
      ||O-Proxy|-(5)-|O-SBE+--(7)-+I-SBE+-(8)--+T-SBE+-(11)-|T-Proxy||
      |+-------+     +-----+      +-----+      +-----+      +-------+|
      |    |               |                   |                |    |
      |   (1)              |                   |               (12)  |
      |    |               |                   |                |    |
      | +-----+      +-----+      +-----+      +-----+       +-----+ |
      | | UAC +=(13)=+0-DBE+======+I-DBE+======+T-DBE+=======+ UAS | |
      | +-----+      +-----+      +-----+      +-----+       +-----+ |
      +--------------------------------------------------------------+
           example.com          example.org          example.net

             Indirect Peering via I-SSP Domain (SIP and media)

                                 Figure 4

   The following is a high-level depiction of the use case:

   1.   UAC initiates a call via SIP INVITE to O-Proxy.  O-Proxy is the
        home proxy for UAC.

         INVITE sip:+19172223333@example.net;user=phone SIP/2.0
         Via: SIP/2.0/TCP client.example.com:5060
           ;branch=z9hG4bK74bf9
         Max-Forwards: 10
         From: Alice <sip:+14083332222@example.com;user=phone>
           ;tag=12345
         To: Bob sip+19172223333@example.net;user=phone
         Call-ID: abcde@client.example.com
         CSeq: 1 INVITE
         Contact: <sip:+19172223333@client.example.com;user=phone
           ;transport=tcp>
         Content-Type: application/sdp

   2.   O-Proxy checks the domain of the R-URI and discovers that the
        UAS's domain is external.  So, it queries LUF for SED
        information from a routing database.  In this example, the LUF
        is an ENUM database.  The ENUM entry looks similar to this:

          $ORIGIN 3.3.3.3.2.2.2.7.1.9.example.net
          NATPTR 10 100 "u" "E2U+SIP"



Uzelac & Lee            Expires October 12, 2008               [Page 14]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


           "!^.* !sip:\\1@i-sbe.example.org!"

        Note that the response shows the next-hop is the SBE in Indirect
        SSP.

        Alternatively, O-SSP may have a pre-association with I-SSP.  As
        such, O-SSP will forward all requests targeting to an external
        domain to I-SSP.  O-SSP will rely on I-SSP to determine T-SSP
        and route the request correctly.  In this setup, O-SSP can skip
        Steps 2,3,4 and 6 and forward the request to I-SBE.  This setup
        is commonly used in Enterprise use cases.

   3.   Routing database entity replies with SED to called party.  In
        this example, the SED is DNS NAPTR record.  The LRF does a DNS
        lookup of the domain name of the NAPTR record and receives a
        response similar to this:

       ;;       order perf flags service    regxp replacement
       IN NAPTR 50    50   "S"   "SIPS+D2T" ""    _sip._tcp.i-sbe.example.org
       IN NAPTR 90    50   "S"   "SIPS+D2U" ""    _sip._udp.i-sbe.example.org

   4.   O-Proxy decides to use TCP for transport protocol, so it sends a
        DNS query for the SRV record for "_sip._tcp.i-sbe.example.org".

        ;;     priority  weight   port  target
        IN SRV 0         1        5060  i-sbe1.example.org
        IN SRV 0         2        5060  i-sbe2.example.org

   5.   Given the O-Proxy's internal routing policy, O-Proxy decides to
        use O-SBE to reach I-SBE, so it routes the INVITE request to
        O-SBE and adds the route header pointing to T-SBE in the INVITE
        request.

         INVITE sip:+19172223333@example.net;user=phone SIP/2.0
         Via: SIP/2.0/TCP o-proxy.example.com:5060
           ;branch=z9hG4bKye8ad
         Via: SIP/2.0/TCP client.example.com:5060
           ;branch=z9hG4bK74bf9;received=192.0.1.1
         Max-Forwards: 9
         Route: <sip:i-sbe1.example.org>
         Record-Route: <sip:o-proxy.example.com;lr>
         From: Alice <sip:+14083332222@example.com;user=phone>
           ;tag=12345
         To: Bob sip+19172223333@example.net;user=phone
         Call-ID: abcde@client.example.com
         CSeq: 1 INVITE
         Contact: <sip:+19172223333@client.example.com;user=phone
           ;transport=tcp>



Uzelac & Lee            Expires October 12, 2008               [Page 15]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


         Content-Type: application/sdp

   6.   O-SBE receives the request and pops the top entry of the Route
        header which contains "i-sbe1.example.org".  O-SBE sends a DNS
        query for "i-sbe1.example.org" to get the A-Record:

          ;; DNS ANSWER
          i-sbe1.example.org   A   192.3.0.100
          i-sbe1.example.org   A   192.3.0.101

   7.   O-SBE sends the INVITE to I-SBE.  O-SBE is the entry point to
        the O-SSP domain, so it should ensure subsequent mid-dialog
        requests traverse via itself.  If O-SBE chooses to act as B2BUA,
        it will terminate the call and generate a new back-to-back
        INVITE request.  If O-SBC chooses to act as proxy, it should
        record-route to stay in the call path.  In this example, O-SBE
        is a B2BUA.

         INVITE sip:+19172223333@example.net;user=phone SIP/2.0
         Via: SIP/2.0/TCP o-sbe1.example.com:5060
           ;branch= z9hG4bK2d4zzz;
         Max-Forwards: 10
         Record-Route: <sip:o-sbe1.example.com:5060;lr>
         From: Alice <sip:+14083332222@example.com;user=phone>
           ;tag=54321
         To: Bob sip:+19172223333@example.net;user=phone
         Call-ID: abcde-osbe1@o-sbe1.example.com
         CSeq: 1 INVITE
         Contact: <sip:+19172223333@o-sbe1.example.com;user=phone
           transport=tcp>
         Content-Type: application/sdp

   8.   Given the R-URI, I-SBE determines the target belongs to T-SSP.
        Since I-SBE is a B2BUA, I-SBE generates a new INVITE request to
        T-SSP.

         INVITE sip:+19172223333@example.net;user=phone SIP/2.0
         Via: SIP/2.0/TCP i-sbe1.example.com:5060
           ;branch= z9hG4bK2d4777;
         Max-Forwards: 10
         Record-Route: <sip:i-sbe1.example.org:5060;lr>
         From: Alice <sip:+14083332222@example.com;user=phone>
           ;tag=54321
         To: Bob sip:+19172223333@example.net;user=phone
         Call-ID: abcde-isbe1@i-sbe1.example.org
         CSeq: 1 INVITE
         Contact: <sip:+19172223333@i-sbe1.example.org;user=phone
           transport=tcp>



Uzelac & Lee            Expires October 12, 2008               [Page 16]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


         Content-Type: application/sdp

        Note that I-SSP wants the media to traverse through the I-DBE,
        I-SBE must modify the SDP in the Offer to point to its DBE.

   9.   T-SBE determines called party home proxy and directs call to
        called party.  T-SBE may use ENUM or other internal mechanism to
        locate the home proxy.  If T-SSP uses ENUM, this internal ENUM
        entry is different from the external ENUM entry populated for
        O-SSP.  For internal use,it should return the home proxy of UAS.
        For external use, it should return T-SBE.

         $ORIGIN 3.3.3.3.2.2.2.7.1.9.example.net
         NATPTR 10 100 "u" "E2U+SIP"
           "!^.* !sip:bob@t-proxy.example.net!"

   10.  T-SBE receives the NAPTR record and query DNS for the "home-
        proxy.example.net".  The DNS returns an A-Record:

          ;; DNS ANSWER
          t-proxy.example.net   A   192.2.1.2

   11.  T-SBE sends the INVITE to UAS's home proxy:

         INVITE sip:+19172223333@example.net;user=phone SIP/2.0
         Via: SIP/2.0/TCP t-sbe1.example.net:5060
           ;branch= z9hG4bK28uyyy;
         Max-Forwards: 10
         Record-Route: <sip:t-sbe1.example.net:5060;lr>
         From: Alice <sip:+14083332222@example.com;user=phone>
           ;tag=54321
         To: Bob sip:+19172223333@example.net;user=phone
         Call-ID: abcde-tsbe1@t-sbe1.example.com
         CSeq: 1 INVITE
         Contact: <sip:+19172223333@t-sbe1.example.com;user=phone
           transport=tcp>
         Content-Type: application/sdp

   12.  Finally, UAS's home proxy forwards the INVITE request to UAS.












Uzelac & Lee            Expires October 12, 2008               [Page 17]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


         INVITE sip:+19172223333@server.example.net;user=phone SIP/2.0
         Via: SIP/2.0/TCP t-proxy.example.net:5060
           ;branch= z9hG4bK28u111;
         Via: SIP/2.0/TCP t-sbe1.example.net:5060
           ;branch= z9hG4bK28uyyy; received=192.2.0.100
         Max-Forwards: 9
         Record-Route: <sip:t-proxy.example.net:5060;lr>,
           <sip:t-sbe1.example.net:5060;lr>
         From: Alice <sip:+14083332222@example.com;user=phone>
           ;tag=54321
         To: Bob sip:+19172223333@example.net;user=phone
         Call-ID: abcde-tsbe1@t-sbe1.example.com
         CSeq: 1 INVITE
         Contact: <sip:+19172223333@t-sbe1.example.com;user=phone
           transport=tcp>
         Content-Type: application/sdp

   13.  RTP is established between UAC and UAS.

5.1.3.1.1.  Administrative characteristics

   The Static Indirect Use Case is implemented in cases where no direct
   interconnection exists between originating and terminating domains
   due to either business or physical constraints.

   O-SSP <---> I-SSP = Relationship O-I

   In the O-I relationship, typical policies, features or functions that
   deem this relationship necessary are number portability, Ubiquity of
   termination options, security certificate management and masquerading
   of originating VoIP network gear.

   T-SSP <---> I-SSP = Relationship T-I

   In the T-I relationship, typical policies, features or functions
   observed consist of codec "scrubbing", anonymizing, and transcoding.
   I-SSP must record-route and stay in the signaling path.  T-SSP will
   not accept message directly sent from O-SSP.

5.1.3.1.2.  Options and Nuances

   Similar to the Static Direct Peering Use Case, O-SSP and T-SSP may
   deploy SBE and DBE for NAT traversal, security, transcoding, etc.
   I-SSP can also deploy SBE and DBE for similar reasons. (as depicted
   in Figure 4)






Uzelac & Lee            Expires October 12, 2008               [Page 18]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


5.1.4.  Static Indirect Peering Use Case - Assisted LUF and LRF

   This use case O-SSP uses A-SP for LUF and LRF and I-SSP to reach
   T-SSP.  A-SP and I-SSP can be the same provider or different
   providers.

                            +------------------+
                            | LUF/LRF Prvoider |
                            |       I-SSP      |
                            |      +-------+   |
                            |   ---+ A-LUF |   |
                            |  /   | A-LRF |   |
       +--------------------+ /    +-------+   +---------------------+
       |       O-SSP        |/     /           |         T-SSP       |
       |      +-------------/     /            |        +-----+      |
       |     /              |    /             |        |T-LUF|      |
       |    /               |  (6)             |   +----+T-LRF|      |
       | (2,3,4)          + +---               |  /     +-----+      |
       |  /              /  |                  | /(9,10)             |
       |+-------+     +-----+     +-----+      +-----+      +-------+|
       ||O-Proxy|-(5)-|O-SBE+-(7)-+I-SBE+-(8)--+T-SBE+-(11)-|T-Proxy||
       |+-------+     +-----+     +-----+      +-----+      +-------+|
       |    |               |                  |                |    |
       |   (1)              |                  |               (12)  |
       |    |               |                  |                |    |
       | +-----+      +-----+     +-----+      +-----+       +-----+ |
       | | UAC +=(13)=|0-DBE+=====+I-DBE+======+T-DBE+=======+ UAS | |
       | +-----+      +-----+     +-----+      +-----+       +-----+ |
       +-------------------------------------------------------------+
            example.com          example.org         example.net

            Indirect Peering via A-SP and I-SSP (SIP and media)

                                 Figure 5

5.1.4.1.  Administrative characteristics

   The major difference from Static Indirect Peering Use Case, Step
   2,3,4 and 6 happen in LUF/LRF provider domain.  O-SSP uses this use
   case when it uses different I-SSP to reach different T-SSP.
   Typically, LUF/LRF provider serves multiple O-SSP.  Two O-SSP may use
   different I-SSP to reach the same T-SSP.  For example, O-SSP1 may use
   I-SSP1 to reach T-SSP, but O-SSP2 may use I-SSP2 to reach T-SSP.  In
   other words, given the O-SSP and T-SSP pair as input, LUF/LRF
   provider will return the SED of I-SSP that is trusted by O-SSP to
   forward the request to T-SSP.

   There are two levels of trust relationship.  First trust relationship



Uzelac & Lee            Expires October 12, 2008               [Page 19]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


   between O-SSP and LUF/LRF provider.  LUF/LRF provider provides LUF
   and LRF for O-SSP.  Once O-SSP queries the SED, LUF/LRF provider is
   out of the picture.  Second trust relationship is between O-SSP and
   I-SSP.  I-SSP provides L5 connectivity to assist O-SSP to reach
   T-SSP.  O-SSP and I-SSP have a pre-association for policy before
   peering happened.  Although Figure 5 shows a single provider to
   provide both LUR/LRF and I-SSP, O-SSP can choose two different
   providers.

5.1.4.2.  Options and Nuances

   In Figure 5, we show I-DBE.  This will be used when O-SSP and T-SSP
   do not have a common code.  To involve I-DBE, I-SSP should know the
   list of codec supported by O-SSP and T-SSP.  When I-SBE receives the
   INVITE, it will make a decision to invoke the I-DBE.  Another
   scenario an I-DBE will be used is if O-SSP uses SRTP [RFC3711] for
   media and T-SSP does not support SRTP, I-DBE can be used.

5.2.  On-demand Peering Use Cases

   On-demand Peering [I-D.ietf-speermint-terminology] describes two SSPs
   form the peering relationship without a pre-arranged agreement.

5.2.1.  On-demand Direct Peering Use Case

   The basis of this use case is built on the fact that there is NOT a
   pre-established relationship between the O-SSP and the T-SSP.  The
   O-SSP and T-SSP did not share any information prior to the dialog
   initiation request.  When the O-Proxy invokes the LUF and LRF on the
   R-URI, the terminating user information must be publicly available.
   Besides, when the O-Proxy routes the request to the T-Proxy, the
   T-Proxy must accept the request without any pre-association with
   O-SSP.

5.2.1.1.  Administrative characteristics

   The On-demand Direct Peering Use Case is typically implemented in a
   scenario where the T-SSP allows any O-SSP to reach its serving
   subscribers.  T-SSP administrative domain does not require any pre-
   arranged agreement to accept the call.  T-SSP makes its subscribers
   information available in public.  This model mimics the Internet
   email model.  Sender does not need an pre-arranged agreement to send
   email to the receiver.

5.2.1.2.  Options and Nuances

   Similar to Static Direct Peering Use Case, O-SSP and T-SSP can decide
   to deploy SBE.  T-SSP is open to the public, T-SSP should prepare to



Uzelac & Lee            Expires October 12, 2008               [Page 20]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


   suffer from the spam problem existing in email system.  VoIP spam is
   considered more annoying than email spam to the subscribers.  T-SSP
   should apply rules to filter spam calls.


6.  Federations

   This section discusses the federation concept, explains which
   technical parameters make up the foundation of a federation and
   provides examples.

   The concrete implementation details (e.g. "direct with one SBE"
   versus "direct with two SBEs") can involve all the use cases thus far
   described in the document.

6.1.  Federation Examples

   This section lists some examples of how federations can operate.

6.1.1.  Trivial Federations

   A private peering arrangement between two SSPs is a special case of a
   federation.  These two SSP have agreed to exchange calls amongst
   themselves and they have set up whatever LUF/LRF/SBE plus Layer 3
   infrastructure they need to route and complete the calls.  This can
   be in a direct or indirect manner, but usually follows the direct
   call model.

   It is thus not needed to treat bi-lateral peering as conceptually
   different to federation-based peering.

   On the other extreme, the set of all SSPs implementing an open SIP
   service according to [RFC3261], [RFC3263], [RFC3761] also fulfills
   the definition of a federation.  In that case, the technical rules
   are contained in these three RFCs, the LS is the public DNS.  Whether
   some of these SSPs use SBCs as border elements is not relevant.

   The administrative model of this federation is the "email model":
   There is no "member list", any SIP server operating on the Internet
   which implements call routing according to these RFCs is implicitly a
   member of that federation.  No business relationship is needed
   between "members", thus no money is likely to change hands for
   terminating calls.  There is no contractual protection against
   nuisance calls, SPIT or denial of service attacks.







Uzelac & Lee            Expires October 12, 2008               [Page 21]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


6.1.2.  Access List based Federations

   If running an open SIP proxy is not desired, then a group of SSPs
   which want to allow calls from each other can collect the list of IP
   addresses of all their border elements.

   This list is redistributed to all members which use it to configure
   firewalls in front of their ingress elements.  Thus calls from other
   members of this federation are accepted while calls from other hosts
   on the Internet are blocked.

   Whether SSPs deploy SBEs as border elements is not relevant.  Call
   routing can still be done via standard RFC rules.

   Whenever a new member joins this club every other SSP needs to adapt
   its filter rules.

6.1.3.  Central SIP Proxy Federations

   One way to simplify the management of these firewall rules is to
   route all SIP messages via a central proxy.

   In that case, all federation members just need to open up their
   ingress elements to requests from that central server.  A new SSP
   just triggers a change in the configuration of this box and not at
   all other SSPs.

   While centralized solutions may entail typical hub-and-spoke
   architecture considerations, the added overall federation scalability
   with respect to the number of interconnects required, their
   associated policies and management make this approach quite popular
   today.

   This is an example of Indirect Peering.

6.1.4.  Architecture, scalability and business scalability

   The network architecture which in the case centralized model would
   reflect a hub and spoke model - should be weighed against a
   distributed model.  While such a centralized model presents well-
   known network and server scalability challenges, a distributed model
   requires higher interconnection complexity, reflected in provisioning
   and the need for the maintenance of such relationships.


7.  Acknowledgments

   This draft is a consolidation of many early individual drafts.



Uzelac & Lee            Expires October 12, 2008               [Page 22]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


   Michael Haberler, Mike Mammer, Otmar Lendl, Rohan Mahy, David
   Schwartz, Eli Katz and Jeremy Barkan are the authors of the early
   individal drafts.  Besides, Jason Livingood, Daryl Malas, David
   Meyer, John Elwell, Reinaldo Penno, Sohel Khan, James, McEachern, Jon
   Peterson, Alexander Mayrhofer, and Jean-Francois Mule made many
   valuable comments to this draft.


8.  Security and Privacy Considerations

   This document introduces no new security considerations.  However, it
   is important to note that session interconnect, as described in this
   document, has a wide variety of security issues that should be
   considered in documents addressing both protocol and use case
   analyzes.


9.  IANA Considerations

   This document creates no new requirements on IANA namespaces RFC 2434
   [RFC2434].


10.  References

10.1.  Normative References

   [I-D.lee-speermint-use-case-cable]
              Lee, Y., "Session Peering Use Case for Cable",
              draft-lee-speermint-use-case-cable-01 (work in progress),
              September 2006.

   [I-D.lendl-speermint-federations]
              Lendl, O., "A Federation based VoIP Peering Architecture",
              draft-lendl-speermint-federations-03 (work in progress),
              September 2006.

   [I-D.mahy-speermint-direct-peering]
              Mahy, R., "A Minimalist Approach to Direct Peering",
              draft-mahy-speermint-direct-peering-02 (work in progress),
              July 2007.

   [I-D.schwartz-speermint-use-cases-federations]
              Schwartz, D., "Session Peering Use Cases for Federations",
              draft-schwartz-speermint-use-cases-federations-00 (work in
              progress), November 2006.

   [I-D.uzelac-speermint-use-cases]



Uzelac & Lee            Expires October 12, 2008               [Page 23]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


              Uzelac, A., "SIP Peering Use Case for VSPs",
              draft-uzelac-speermint-use-cases-00 (work in progress),
              October 2006.

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

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [RFC3261]  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.

   [RFC3263]  Rosenberg, J. and H. Schulzrinne, "Session Initiation
              Protocol (SIP): Locating SIP Servers", RFC 3263,
              June 2002.

   [RFC3761]  Faltstrom, P. and M. Mealling, "The E.164 to Uniform
              Resource Identifiers (URI) Dynamic Delegation Discovery
              System (DDDS) Application (ENUM)", RFC 3761, April 2004.

10.2.  Informative References

   [I-D.lewis-peppermint-enum-reg-if]
              Lewis, E., "ENUM Registry Interface Requirements",
              draft-lewis-peppermint-enum-reg-if-01 (work in progress),
              November 2007.

   [I-D.newton-peppermint-problem-statement]
              Newton, A., "Provisioning Extensions in Peering Registries
              for Multimedia Interconnection  (PEPPERMINT) Problem
              Statement", draft-newton-peppermint-problem-statement-00
              (work in progress), January 2007.

   [RFC3546]  Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
              and T. Wright, "Transport Layer Security (TLS)



Uzelac & Lee            Expires October 12, 2008               [Page 24]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


              Extensions", RFC 3546, June 2003.

   [RFC3711]  Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
              Norrman, "The Secure Real-time Transport Protocol (SRTP)",
              RFC 3711, March 2004.


Authors' Addresses

   Adam Uzelac (editor)
   Global Crossing
   U.S.A.

   Phone:
   Email: adam.uzelac@globalcrossing.com
   URI:   http://www.globalcrossing.com


   Yiu L.Lee (editor)
   Comcast Cable
   U.S.A.

   Phone:
   Email: yiu_lee@cable.comcast.com
   URI:   http://www.comcast.com


























Uzelac & Lee            Expires October 12, 2008               [Page 25]

Internet-Draft         VoIP SIP Peering Use Cases             April 2008


Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.











Uzelac & Lee            Expires October 12, 2008               [Page 26]


Html markup produced by rfcmarkup 1.109, available from https://tools.ietf.org/tools/rfcmarkup/