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MBONED Working Group                                  Percy S. Tarapore
Internet Draft                                             Robert Sayko
Intended status: BCP                                               AT&T
Expires: August 3, 2014                                   Greg Shepherd
                                                        Toerless Eckert
                                                                  Cisco
                                                           Ram Krishnan
                                                                 Brocade
                                                           March 3, 2014


       Multicasting Applications Across Inter-Domain Peering Points
                draft-tarapore-mboned-multicast-cdni-05.txt


Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on August 3, 2014.

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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Abstract

   This document examines the process of transporting applications via
   multicast across inter-domain peering points. The objective is to
   describe the setup process for multicast-based delivery across
   administrative domains and document supporting functionality to
   enable this process.

Table of Contents


   1. Introduction...................................................3
   2. Overview of Inter-domain Multicast Application Transport.......3
   3. Inter-domain Peering Point Requirements for Multicast..........5
      3.1. Native Multicast..........................................5
      3.2. Peering Point Enabled with GRE Tunnel.....................6
      3.3. Peering Point Enabled with an AMT - Both Domains Multicast
      Enabled........................................................8
      3.4. Peering Point Enabled with an AMT - AD-2 Not Multicast
      Enabled........................................................9
      3.5. AD-2 Not Multicast Enabled - Multiple AMT Tunnels Through
      AD-2..........................................................11
   4. Supporting Functionality......................................13
      4.1. Network Interconnection Transport and Security Guidelines14
      4.2. Routing Aspects and Related Guidelines...................15
         4.2.1    Native Multicast Routing Aspects..................15
         4.2.2    GRE Tunnel over Interconnecting Peering Point.....16
         4.2.3 Routing Aspects with AMT Tunnels.....................16
      4.3. Back Office Functions - Billing and Logging Guidelines...19
      4.4. Operations - Service Performance and Monitoring Guidelines19
      4.5. Reliability Models/Service Assurance Guidelines..........19
      4.6. Provisioning Guidelines..................................19
      4.7. Client Models............................................19
      4.8. Addressing Guidelines....................................19
   5. Security Considerations.......................................19


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   6. IANA Considerations...........................................20
   7. Conclusions...................................................20
   8. References....................................................20
      8.1. Normative References.....................................20
      8.2. Informative References...................................20
   9. Acknowledgments...............................................20

   1. Introduction

   Several types of applications (e.g., live video streaming, software
   downloads) are well suited for delivery via multicast means. The use
   of multicast for delivering such applications offers significant
   savings for utilization of resources in any given administrative
   domain. End user demand for such applications is growing. Often,
   this requires transporting such applications across administrative
   domains via inter-domain peering points.

   The objective of this Best Current Practices document is twofold:
     o Describe the process and establish guidelines for setting up
        multicast-based delivery of applications across inter-domain
        peering points, and
     o Catalog  all  required  information  exchange  between  the
        administrative domains to support multicast-based delivery.

   While there are several multicast protocols available for use, this
   BCP will focus the discussion to those that are applicable and
   recommended for the peering requirements of today's service model,
   including:

     o Protocol  Independent  Multicast  -  Source  Specific  Multicast
        (PIM-SSM) [RFC4607]
     o Internet Group Management Protocol (IGMP) v3 [RFC4604]
     o Multicast Listener Discovery (MLD) [RFC4604]

   This document therefore serves the purpose of a "Gap Analysis"
   exercise for this process. The rectification of any gaps identified
   - whether they involve protocol extension development or otherwise -
   is beyond the scope of this document and is for further study.

   2. Overview of Inter-domain Multicast Application Transport

   A multicast-based application delivery scenario is as follows:




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     o Two independent administrative domains are interconnected via a
        peering point.
     o The peering point is either multicast enabled (end-to-end
        native multicast across the two domains) or it is connected by
        one of two possible tunnel types:
       o A Generic Routing Encapsulation (GRE) Tunnel [RFC2784]
          allowing multicast tunneling across the peering point, or
       o An Automatic Multicast Tunnel (AMT) [IETF-ID-AMT].
     o The application stream originates at a source in Domain 1.
     o An End User associated with Domain 2 requests the application.
        It is assumed that the application is suitable for delivery via
        multicast means (e.g., live steaming of major events, software
        downloads to large numbers of end user devices, etc.)
     o The request is communicated to the application source which
        provides the relevant multicast delivery information to the EU
        device via a "manifest file". At a minimum, this file contains
        the {Source, Group} or (S,G) information relevant to the
        multicast stream.
     o The application client in the EU device then joins the
        multicast stream distributed by the application source in
        domain 1 utilizing the (S,G) information provided in the
        manifest file. The manifest file may also contain additional
        information that the application client can use to locate the
        source and join the stream.

   It should be noted that the second administrative domain - domain 2
   - may be an independent network domain (e.g., Tier 1 network
   operator domain) or it could also be an Enterprise network operated
   by a single customer. The peering point architecture and
   requirements may have some unique aspects associated with the
   Enterprise case.

   The Use Cases describing various architectural configurations for
   the multicast distribution along with associated requirements is
   described in section 3. Unique aspects related to the Enterprise
   network possibility will be described in this section. A
   comprehensive list of pertinent information that needs to be
   exchanged between the two domains to support various functions
   enabling the application transport is provided in section 4.



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   3. Inter-domain Peering Point Requirements for Multicast

   The transport of applications using multicast requires that the
   inter-domain peering point is enabled to support such a process.
   There are three possible Use Cases for consideration.

   3.1. Native Multicast

   This Use Case involves end-to-end Native Multicast between the two
   administrative domains and the peering point is also native
   multicast enabled - Figure 1.



      -------------------               -------------------
     /       AD-1        \             /        AD-2       \
    / (Multicast Enabled) \           / (Multicast Enabled) \
   /                       \         /                       \
   | +----+                |         |                       |
   | |    |       +------+ |         |  +------+             |   +----+
   | | CS |------>|  BR  |-|---------|->|  BR  |-------------|-->| EU |
   | |    |       +------+ |   I1    |  +------+             |I2 +----+
   \ +----+                /         \                       /
    \                     /           \                     /
     \                   /             \                   /
      -------------------               -------------------


   AD = Administrative Domain (Independent Autonomous System)
   CS = Content Multicast Source
   BR = Border Router
   I1 = AD-1 and AD-2 Multicast Interconnection (MBGP or BGMP)
   I2 = AD-2 and EU Multicast Connection

      Figure 1 - Content Distribution via End to End Native Multicast


   Advantages of this configuration are:

     o Most efficient use of bandwidth in both domains

     o Fewer devices in the path traversed by the multicast stream
        when compared to unicast transmissions.

   From the perspective of AD-1, the one disadvantage associated with
   native multicast into AD-2 instead of individual unicast to every EU



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   in AD-2 is that it does not have the ability to count the number of
   End Users as well as the transmitted bytes delivered to them. This
   information is relevant from the perspective of customer billing and
   operational logs. It is assumed that such data will be collected by
   the application layer. The application layer mechanisms for
   generating this information need to be robust enough such that all
   pertinent requirements for the source provider and the AD operator
   are satisfactorily met. The specifics of these methods are beyond
   the scope of this document.

   Architectural guidelines for this configuration are as follows:

     a. Dual homing for peering points between domains is recommended
        as a way to ensure reliability with full BGP table visibility.

     b. If the peering point between AD-1 and AD-2 is a controlled
        network   environment,   then   bandwidth   can   be   allocated
        accordingly by the two domains to permit the transit of non-
        rate adaptive multicast traffic. If this is not the case, then
        it is recommended that the multicast traffic should support
        rate-adaption.

     c. The sending and receiving of multicast traffic between two
        domains is typically determined by local policies associated
        with each domain. For example, if AD-1 is a service provider
        and AD-2 is an enterprise, then AD-1 may support local policies
        for traffic delivery to, but not traffic reception from AD-2.

     d. Relevant information on multicast streams delivered to End
        Users  in  AD-2  is  assumed  to  be  collected  by  available
        capabilities in the application layer. The precise nature and
        formats of the collected information will be determined by
        directives from the source owner and the domain operators.



   3.2. Peering Point Enabled with GRE Tunnel

   The peering point is not native multicast enabled in this Use Case.
   There is a Generic Routing Encapsulation Tunnel provisioned over the
   peering point. In this case, the interconnection I1 between AD-1 and
   AD-2 in Figure 1 is multicast enabled via a Generic Routing
   Encapsulation Tunnel (GRE) [RFC2784] and encapsulating the multicast
   protocols across the interface. The routing configuration is
   basically unchanged: Instead of BGP (SAFI2) across the native IP


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   multicast link between AD-1 and AD-2, BGP (SAFI2) is now run across
   the GRE tunnel.

   Advantages of this configuration:

     o Highly efficient use of bandwidth in both domains although not
        as efficient as the fully native multicast Use Case.

     o Fewer devices in the path traversed by the multicast stream
        when compared to unicast transmissions.

     o Ability to support only partial IP multicast deployments in AD-
        1 and/or AD-2.

     o GRE is an existing technology and is relatively simple to
        implement.

   Disadvantages of this configuration:

     o Per Use Case 3.1, current router technology cannot count the
        number of end users or the number bytes transmitted.

     o GRE tunnel requires manual configuration.

     o GRE must be in place prior to stream starting.

     o GRE is often left pinned up

   Architectural guidelines for this configuration include the
   following:

   Guidelines (a) through (d) are the same as those described in Use
   Case 3.1.

     e. GRE tunnels are typically configured manually between peering
        points to support multicast delivery between domains.
     f. It  is  recommended  that  the  GRE  tunnel  (tunnel  server)
        configuration in the source network is such that it only
        advertises the routes to the content sources and not to the
        entire  network.  This  practice  will  prevent  unauthorized
        delivery of content through the tunnel (e.g., if content is not
        part of an agreed CDN partnership).





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   3.3. Peering Point Enabled with an AMT - Both Domains Multicast
      Enabled

   Both administrative domains in this Use Case are assumed to be
   native multicast enabled here; however the peering point is not. The
   peering point is enabled with an Automatic Multicast Tunnel. The
   basic configuration is depicted in Figure 2.



      -------------------               -------------------
     /       AD-1        \             /       AD-2        \
    / (Multicast Enabled) \           / (Multicast Enabled) \
   /                       \         /                       \
   | +----+                |         |                       |
   | |    |       +------+ |         |  +------+             |   +----+
   | | CS |------>|  AR  |-|---------|->|  AG  |-------------|-->| EU |
   | |    |       +------+ |   I1    |  +------+             |I2 +----+
   \ +----+                /         \                       /
    \                     /           \                     /
     \                   /             \                   /
      -------------------               -------------------


   AR = AMT Relay
   AG = AMT Gateway
   I1 = AMT Interconnection between P-CDN and S-CDN
   I2 = S-CDN and EU Multicast Connection

           Figure 2 - AMT Interconnection between AD-1 and AD-2

   Advantages of this configuration:

     o Highly efficient use of bandwidth in AD-1.

     o AMT is an existing technology and is relatively simple to
        implement. Attractive properties of AMT include the following:

          o Dynamic interconnection between Gateway-Relay pair across
             the peering point.

          o Ability  to  serve  clients  and  servers  with  differing
             policies.

   Disadvantages of this configuration:



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     o Per Use Case 3.1 (AD-2 is native multicast), current router
        technology cannot count the number of end users or the number
        bytes transmitted.

     o Additional  devices  (AMT  Gateway  and  Relay  pairs)  may  be
        introduced into the path if these services are not incorporated
        in the existing routing nodes.

     o Currently undefined mechanisms to select the AR from the AG
        automatically.

   Architectural guidelines for this configuration are as follows:

   Guidelines (a) through (d) are the same as those described in Use
   Case 3.1.

     e. It is recommended that AMT Relay and Gateway pairs be
     configured at the peering points to support multicast delivery
     between domains. AMT tunnels will then configure dynamically
     across the peering points once the Gateway in AD-2 receives the
     (S, G) information from the EU.



   3.4. Peering Point Enabled with an AMT - AD-2 Not Multicast Enabled

   In this AMT Use Case, the second administrative domain AD-2 is not
   multicast enabled. This implies that the interconnection between AD-
   2 and the End User is also not multicast enabled as depicted in
   Figure 3.


















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      -------------------               -------------------
     /        AD-1       \             /        AD-2       \
    / (Multicast Enabled) \           /   (Non-Multicast    \
   /                       \         /       Enabled)        \
   | +----+                |         |                       |
   | |    |       +------+ |         |                       |   +----+
   | | CS |------>|  AR  |-|---------|-----------------------|-->|EU/G|
   | |    |       +------+ |         |                       |I2 +----+
   \ +----+                /         \                       /
    \                     /           \                     /
     \                   /             \                   /
      -------------------               -------------------


   CS = Content Source
   AR = AMT Relay
   EU/G = Gateway client embedded in EU device
   I2 = AMT Tunnel Connecting EU/G to AR in AD-1 through Non-Multicast
      Enabled AD-2.

      Figure 3 - AMT Tunnel Connecting AD-1 AMT Relay and EU Gateway


   This Use Case is equivalent to having unicast distribution of the
   application through AD-2. The total number of AMT tunnels would be
   equal to the total number of End Users requesting the application.
   The peering point thus needs to accommodate the total number of AMT
   tunnels between the two domains. Each AMT tunnel can provide the
   data usage associated with each End User.

   Advantages of this configuration:

     o Highly efficient use of bandwidth in AD-1.

     o AMT is an existing technology and is relatively simple to
        implement. Attractive properties of AMT include the following:

          o Dynamic interconnection between Gateway-Relay pair across
             the peering point.

          o Ability  to  serve  clients  and  servers  with  differing
             policies.

     o Each AMT tunnel serves as a count for each End User and is also
        able to track data usage (bytes) delivered to the EU.


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   Disadvantages of this configuration:

     o Additional devices (AMT Gateway and Relay pairs) are introduced
        into the transport path.

     o Assuming multiple peering points between the domains, the EU
        Gateway needs to be able to find the "correct" AMT Relay in AD-
        1.

   Architectural guidelines for this configuration are as follows:

   Guidelines (a) through (c) are the same as those described in Use
   Case 3.1.

     d. It is recommended that proper procedures are implemented such
     that the AMT Gateway at the End User device is able to find the
     correct AMT Relay in AD-1 across the peering points. The
     application client in the EU device is expected to supply the (S,
     G) information to the Gateway for this purpose.

     e. The AMT tunnel capabilities are expected to be sufficient for
     the purpose of collecting relevant information on the multicast
     streams delivered to End Users in AD-2.



3.5. AD-2 Not Multicast Enabled - Multiple AMT Tunnels Through AD-2

   This is a variation of Use Case 3.4 as follows:



















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      -------------------               -------------------
     /        AD-1       \             /        AD-2       \
    / (Multicast Enabled) \           /   (Non-Multicast    \
   /                       \         /       Enabled)        \
   | +----+                |         |+--+              +--+ |
   | |    |       +------+ |         ||AG|              |AG| |   +----+
   | | CS |------>|  AR  |-|-------->||AR|------------->|AR|-|-->|EU/G|
   | |    |       +------+ |   I1    ||1 |      I2      |2 | |I3 +----+
   \ +----+                /         \+--+              +--+ /
    \                     /           \                     /
     \                   /             \                   /
      -------------------               -------------------

   (Note: Diff-marks for the figure have been removed to improve
      viewing)

   CS = Content Source
   AR = AMT Relay in AD-1
   AGAR1 = AMT Gateway/Relay node in AD-2 across Peering Point
   I1 = AMT Tunnel Connecting AR in AD-1 to GW in AGAR1 in AD-2
   AGAR2 = AMT Gateway/Relay node at AD-2 Network Edge
   I2 = AMT Tunnel Connecting Relay in AGAR1 to GW in AGAR2
   EU/G = Gateway client embedded in EU device
   I3 = AMT Tunnel Connecting EU/G to AR in AGAR2

      Figure 4 - AMT Tunnel Connecting AD-1 AMT Relay and EU Gateway


   Use Case 3.4 results in several long AMT tunnels crossing the entire
   network of AD-2 linking the EU device and the AMT Relay in AD-1
   through the peering point. Depending on the number of End Users,
   there is a likelihood of an unacceptably large number of AMT tunnels
   - and unicast streams - through the peering point. This situation
   can be alleviated as follows:

     o Provisioning of strategically located AMT nodes at the edges of
        AD-2. An AMT node comprises co-location of an AMT Gateway and
        an AMT Relay. One such node is at the AD-2 side of the peering
        point (node AGAR1 in Figure 4).

     o Single AMT tunnel established across peering point linking AMT
        Relay in AD-1 to the AMT Gateway in the AMT node AGAR1 in AD-2.

     o AMT tunnels linking AMT node AGAR1 at peering point in AD-2 to
        other AMT nodes located at the edges of AD-2: e.g., AMT tunnel


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        I2 linking AMT Relay in AGAR1 to AMT Gateway in AMT node AGAR2
        in Figure 4.

     o AMT tunnels linking EU device (via Gateway client embedded in
        device) and AMT Relay in appropriate AMT node at edge of AD-2:
        e.g., I3 linking EU Gateway in device to AMT Relay in AMT node
        AGAR2.

   The advantage for such a chained set of AMT tunnels is that the
   total number of unicast streams across AD-2 is significantly reduced
   thus freeing up bandwidth. Additionally, there will be a single
   unicast stream across the peering point instead of possibly, an
   unacceptably large number of such streams per Use Case 3.4. However,
   this implies that several AMT tunnels will need to be dynamically
   configured by the various AMT Gateways based solely on the (S,G)
   information received from the application client at the EU device. A
   suitable mechanism for such dynamic configurations is therefore
   critical.

   Architectural guidelines for this configuration are as follows:

   Guidelines (a) through (c) are the same as those described in Use
   Case 3.1.

     d. It is recommended that proper procedures are implemented such
     that the various AMT Gateways (at the End User devices and the AMT
     nodes in AD-2) are able to find the correct AMT Relay in other AMT
     nodes as appropriate. The application client in the EU device is
     expected to supply the (S, G) information to the Gateway for this
     purpose.

     e. The AMT tunnel capabilities are expected to be sufficient for
     the purpose of collecting relevant information on the multicast
     streams delivered to End Users in AD-2.



   4. Supporting Functionality

   Supporting functions and related interfaces over the peering point
   that enable the multicast transport of the application are listed in
   this section. Critical information parameters that need to be
   exchanged in support of these functions are enumerated along with
   guidelines as appropriate. Specific interface functions for
   consideration are as follows.



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   4.1. Network Interconnection Transport and Security Guidelines

   The term "Network Interconnection Transport" refers to the
   interconnection points between the two Administrative Domains. The
   following is a representative set of attributes that will need to be
   agreed to between the two administrative domains to support
   multicast delivery.

     o Number of Peering Points

     o Peering Point Addresses and Locations

     o Connection Type - Dedicated for Multicast delivery or shared
        with other services

     o Connection Mode - Direct connectivity between the two AD's or
        via another ISP

     o Peering Point Protocol Support - Multicast protocols that will
        be used for multicast delivery will need to be supported at
        these points. Examples of protocols include eBGP, BGMP, and
        MBGP.

     o Bandwidth Allocation - If shared with other services, then
        there needs to be a determination of the share of bandwidth
        reserved for multicast delivery.

     o QoS Requirements - Delay/latency specifications that need to be
        specified in an SLA.

     o AD Roles and Responsibilities - the role played by each AD for
        provisioning and maintaining the set of peering points to
        support multicast delivery.

   From a security perspective, it is expected that normal/typical
   security procedures will be followed by each AD to facilitate
   multicast delivery to registered and authenticated end users. Some
   security aspects for consideration are:

     o Encryption - Peering point links may be encrypted per agreement
        if dedicated for multicast delivery.

     o Security Breach Mitigation Plan - In the event of a security
        breach, the two AD's are expected to have a mitigation plan for
        shutting down the peering point and directing multicast traffic


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        over  alternated  peering  points.  It  is  also  expected  that
        appropriate information will be shared for the purpose of
        securing the identified breach.



   4.2. Routing Aspects and Related Guidelines

   The main objective for multicast delivery routing is to ensure that
   the End User receives the multicast stream from the "most optimal"
   source [INF_ATIS_10] which typically:

     o Maximizes the multicast portion of the transport and minimizes
        any unicast portion of the delivery, and

     o Minimizes the overall combined network(s) route distance.

   This routing objective applies to both Native and AMT; the actual
   methodology of the solution will be different for each. Regardless,
   the routing solution is expected to be:

      o Scalable

      o Avoid/minimize new protocol development or modifications, and

      o Be robust enough to achieve high reliability and automatically
         adjust to changes/problems in the multicast infrastructure.

   For both Native and AMT environments, having a source as close as
   possible to the EU network is most desirable; therefore, in some
   cases, an AD may prefer to have multiple sources near different
   peering points, but that is entirely an implementation issue.

   4.2.1 Native Multicast Routing Aspects

   Native multicast simply requires that the Administrative Domains
   coordinate and advertise the correct source address(es) at their
   network interconnection peering points(i.e., border routers). An
   example of multicast delivery via a Native Multicast process across
   two administrative Domains is as follows assuming that the
   interconnecting peering points are also multicast enabled:

     o Appropriate information is obtained by the EU client who is a
       subscriber to AD-2 (see Use Case 3.1). This is usually done via
       an appropriate file transfer - this file is typically known as
       the manifest file. It contains instructions directing the EU


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       client to launch an appropriate application if necessary, and
       also additional information for the application about the source
       location and the group (or stream) id in the form of the "S,G"
       data. The "S" portion provides the name or IP address of the
       source of the multicast stream. The file may also contain
       alternate delivery information such as specifying the unicast
       address of the stream.

     o The client uses the join message with S,G to join the multicast
       stream [RFC2236].

   To facilitate this process, the two AD's need to do the following:

     o Advertise the source id(s) over the Peering Points

     o Exchange relevant Peering Point information such as Capacity
        and Utilization (Other??)

   4.2.2 GRE Tunnel over Interconnecting Peering Point

   If the interconnecting peering point is not multicast enabled and
   both ADs are multicast enabled, then a simple solution is to
   provision a GRE tunnel between the two ADs - see Use Case 3.2.2.
   The termination points of the tunnel will usually be a network
   engineering decision, but generally will be between the border
   routers or even between the AD 2 border router and the AD 1 source
   (or source access router). The GRE tunnel would allow end-to-end
   native multicast or AMT multicast to traverse the interface.
   Coordination and advertisement of the source IP is still required.

   The two AD's need to follow the same process as described in 4.2.1
   to facilitate multicast delivery across the Peering Points.

   4.2.3 Routing Aspects with AMT Tunnels

   Unlike Native (with or without GRE), an AMT Multicast environment is
   more complex. It presents a dual layered problem because there are
   two criteria that should be simultaneously meet:

     o Find the closest AMT relay to the end-user that also has
        multicast connectivity to the content source and

     o Minimize the AMT unicast tunnel distance.

   There are essentially two components to the AMT specification:



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     o AMT Relays: These serve the purpose of tunneling UDP multicast
       traffic to the receivers (i.e., End Points). The AMT Relay will
       receive the traffic natively from the multicast media source and
       will replicate the stream on behalf of the downstream AMT
       Gateways, encapsulating the multicast packets into unicast
       packets and sending them over the tunnel toward the AMT Gateway.
       In addition, the AMT Relay may perform various usage and
       activity statistics collection. This results in moving the
       replication point closer to the end user, and cuts down on
       traffic across the network. Thus, the linear costs of adding
       unicast subscribers can be avoided. However, unicast replication
       is still required for each requesting endpoint within the
       unicast-only network.

     o AMT Gateway (GW): The Gateway will reside on an on End-Point -
       this may be a Personal Computer (PC) or a Set Top Box (STB). The
       AMT Gateway receives join and leave requests from the
       Application via an Application Programming Interface (API). In
       this manner, the Gateway allows the endpoint to conduct itself
       as a true Multicast End-Point. The AMT Gateway will encapsulate
       AMT messages into UDP packets and send them through a tunnel
       (across the unicast-only infrastructure) to the AMT Relay.

   The simplest AMT Use Case (section 3.3) involves peering points that
   are not multicast enabled between two multicast enabled ADs. An AMT
   tunnel is deployed between an AMT Relay on the AD 1 side of the
   peering point and an AMT Gateway on the AD 2 side of the peering
   point. One advantage to this arrangement is that the tunnel is
   established on an as needed basis and need not be a provisioned
   element. The two ADs can coordinate and advertise special AMT Relay
   Anycast addresses with each other - though they may alternately
   decide to simply provision Relay addresses, though this would not be
   a optimal solution in terms of scalability.

   Use Cases 3.4 and 3.5 describe more complicated AMT situations as
   AD-2 is not multicast enabled. For these cases, the End User device
   needs to be able to setup an AMT tunnel in the most optimal manner.
   Using an Anycast IP address for AMT Relays allows for all AMT
   Gateways to find the "closest" AMT Relay - the nearest edge of the
   multicast topology of the source.  An example of a basic delivery
   via an AMT Multicast process for these two Use Cases is as follows:

  o The manifest file is obtained by the EU client application. This
     file contains instructions directing the EU client to an ordered
     list of particular destinations to seek the requested stream and,
     for multicast, specifies the source location and the group (or
     stream) ID in the form of the "S,G" data. The "S" portion provides


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     the URI (name or IP address) of the source of the multicast stream
     and the "G" identifies the particular stream originated by that
     source. The manifest file may also contain alternate delivery
     information such as the address of the unicast form of the content
     to be used, for example, if the multicast stream becomes
     unavailable.

  o Using the information in the manifest file, and possibly
     information provisioned directly in the EU client, a DNS query is
     initiated in order to connect the EU client/AMT Gateway to an AMT
     Relay.

  o Query results are obtained, and may return an Anycast address or a
     specific unicast address of a relay. Multiple relays will
     typically exist. The Anycast address is a routable "pseudo-
     address" shared among the relays that can gain multicast access to
     the source.

  o If a specific IP address unique to a relay was not obtained, the
     AMT Gateway then sends a message (e.g., the discovery message) to
     the Anycast address such that the network is making the routing
     choice of particular relay - e.g., closest relay to the EU. (Note
     that in IPv6 there is a specific Anycast format and Anycast is
     inherent in IPv6 routing, whereas in IPv4 Anycast is handled via
     provisioning in the network. Details are out of scope for this
     document.)

  o The contacted AMT Relay then returns its specific unicast IP
     address (after which the Anycast address is no longer required).
     Variations may exist as well.

  o The AMT Gateway uses that unicast IP address to initiate a three-
     way handshake with the AMT Relay.

  o AMT Gateway provides "S,G" to the AMT Relay (embedded in AMT
     protocol messages).

  o AMT Relay receives the "S,G" information and uses the S,G to join
     the appropriate multicast stream, if it has not already subscribed
     to that stream.

  o AMT Relay encapsulates the multicast stream into the tunnel
     between the Relay and the Gateway, providing the requested content
     to the EU.





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   Note: Further routing discussion on optimal method to find "best AMT
   Relay/GW combination" and information exchange between AD's to be
   provided.

   4.3. Back Office Functions - Billing and Logging Guidelines





   4.4. Operations - Service Performance and Monitoring Guidelines





   4.5. Reliability Models/Service Assurance Guidelines





   4.6. Provisioning Guidelines

   In order to find right relay there is a need for a small/light
   implementation of an AMT DNS in source network.



   4.7. Client Models





   4.8. Addressing Guidelines







   5. Security Considerations

   (Include discussion on DRM, AAA, Network Security)



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   6. IANA Considerations



   7. Conclusions



   8. References

   8.1. Normative References

   [RFC2784]   D. Farinacci, T. Li, S. Hanks, D. Meyer, P. Traina,
   "Generic Routing Encapsulation (GRE)", RFC 2784, March 2000

   [IETF-ID-AMT] G. Bumgardner, "Automatic Multicast Tunneling", draft-
   ietf-mboned-auto-multicast-13, April 2012, Work in progress

   [RFC4604] H. Holbrook, et al, "Using Internet Group Management
   Protocol Version 3 (IGMPv3) and Multicast Listener Discovery
   Protocol Version 2 (MLDv2) for Source Specific Multicast", RFC 4604,
   August 2006

   [RFC4607] H. Holbrook, et al, "Source Specific Multicast", RFC 4607,
   August 2006

   8.2. Informative References

   [INF_ATIS_10] "CDN Interconnection Use Cases and Requirements in a
   Multi-Party Federation Environment", ATIS Standard A-0200010,
   December 2012

   9. Acknowledgments










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   Authors' Addresses

   Percy S. Tarapore
   AT&T
   Phone: 1-732-420-4172
   Email: tarapore@att.com

   Robert Sayko
   AT&T
   Phone: 1-732-420-3292
   Email: rs1983@att.com

   Greg Shepherd
   Cisco
   Phone:
   Email: shep@cisco.com

   Toerless Eckert
   Cisco
   Phone:
   Email: eckert@cisco.com

   Ram Krishnan
   Brocade
   Phone:
   Email: ramk@brocade.com























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