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Versions: 00 01 02                                                      
CDNI WG                                                  S. Previdi, Ed.
Internet-Draft                                            F. Le Faucheur
Intended status: Standards Track                               J. Medved
Expires: March 23, 2013                              Cisco Systems, Inc.
                                                              A. Guillou
                                                                     SFR
                                                      September 19, 2012


                      CDNI Footprint Advertisement
             draft-previdi-cdni-footprint-advertisement-02

Abstract

   This document describes the use of BGP for Content Delivery Networks
   (CDNs) in order to advertise information about footprint and
   connectivity to footprint in the context of CDNI.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on March 23, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  CDNI Mesh and MP-BGP . . . . . . . . . . . . . . . . . . . . .  5
   4.  CDNI Information . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Footprint  . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.2.  Footprint Elements (FPE) . . . . . . . . . . . . . . . . .  6
     4.3.  Footprint Reachability (FPR) . . . . . . . . . . . . . . .  7
     4.4.  CDN Capability Information (CAP) . . . . . . . . . . . . .  7
   5.  CDNI Functional Components . . . . . . . . . . . . . . . . . .  8
     5.1.  CDNI Databases . . . . . . . . . . . . . . . . . . . . . .  8
       5.1.1.  CDNI Footprint Elements Database . . . . . . . . . . .  8
       5.1.2.  CDNI Footprint Reachability Database . . . . . . . . .  9
       5.1.3.  CDNI Capability Database . . . . . . . . . . . . . . .  9
     5.2.  CDNI MP-BGP Messages . . . . . . . . . . . . . . . . . . .  9
       5.2.1.  CDNI MP-BGP Footprint Element Advertisement  . . . . .  9
       5.2.2.  CDNI MP-BGP Footprint Reachability Advertisement . . . 10
       5.2.3.  CDNI Capability Advertisement  . . . . . . . . . . . . 10
     5.3.  CDNI Information Elements (Attributes) . . . . . . . . . . 10
       5.3.1.  CDN Identifier . . . . . . . . . . . . . . . . . . . . 10
       5.3.2.  Footprint Element Identifier . . . . . . . . . . . . . 10
       5.3.3.  Reachable Footprint Element  . . . . . . . . . . . . . 11
       5.3.4.  Origin_AS_PATH . . . . . . . . . . . . . . . . . . . . 11
       5.3.5.  CDN Capabilities . . . . . . . . . . . . . . . . . . . 11
     5.4.  CDNI MP-BGP NLRIs  . . . . . . . . . . . . . . . . . . . . 11
   6.  CDNI Example . . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.1.  Topology . . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.2.  CDN2 Footprint Element Advertisements  . . . . . . . . . . 12
     6.3.  Footprint Element Database in each CDN . . . . . . . . . . 13
     6.4.  Footprint Reachability Advertisements  . . . . . . . . . . 14
     6.5.  Capability Advertisements  . . . . . . . . . . . . . . . . 16
     6.6.  FPE, FPR and CAP Databases in uCDN . . . . . . . . . . . . 16
     6.7.  Request Routing for user 2.2.2.2 . . . . . . . . . . . . . 17
     6.8.  Request Routing for user 1.1.1.1 . . . . . . . . . . . . . 18
   7.  CDNI MP-BGP Encodings  . . . . . . . . . . . . . . . . . . . . 19
     7.1.  CDNI Attributes  . . . . . . . . . . . . . . . . . . . . . 19
       7.1.1.  CDNI Identifier  . . . . . . . . . . . . . . . . . . . 19
       7.1.2.  FPE Identifier . . . . . . . . . . . . . . . . . . . . 19



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       7.1.3.  Origin_AS_PATH . . . . . . . . . . . . . . . . . . . . 19
       7.1.4.  Capabilities . . . . . . . . . . . . . . . . . . . . . 20
     7.2.  CDNI Messages  . . . . . . . . . . . . . . . . . . . . . . 20
       7.2.1.  FPE Advertisement  . . . . . . . . . . . . . . . . . . 20
       7.2.2.  FPR Advertisement  . . . . . . . . . . . . . . . . . . 21
       7.2.3.  CAP Advertisement  . . . . . . . . . . . . . . . . . . 21
     7.3.  CDNI NLRI  . . . . . . . . . . . . . . . . . . . . . . . . 22
       7.3.1.  CDNI-NLRI Type 1: FPE Advertisement  . . . . . . . . . 22
       7.3.2.  CDNI-NLRI Type 2: FPR Advertisement  . . . . . . . . . 23
       7.3.3.  CDNI-NLRI Type 3: CAP Advertisement  . . . . . . . . . 23
       7.3.4.  NLRI Encoding  . . . . . . . . . . . . . . . . . . . . 24
   8.  Compliance with CDNI Requirements  . . . . . . . . . . . . . . 25
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 25
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 25
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 25
     12.2. Informative References . . . . . . . . . . . . . . . . . . 26
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26
































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1.  Introduction

   The IETF CDN Interconnection (CDNI) Working Group is chartered to
   develop specifications for interconnecting standalone CDNs so that
   their collective CDN footprint can be leveraged for the end-to-end
   delivery of content from Content Service Providers (CSPs) to End
   Users.

   [I-D.jenkins-cdni-problem-statement] outlines the problem area that
   the CDNI working group is chartered to address.
   [I-D.bertrand-cdni-use-cases] discusses the use cases for CDN
   Interconnection and [I-D.davie-cdni-framework] discusses the
   technology framework for the CDNI solution and interfaces.

   When an upstream CDN (uCDN) receives a request from a user, it has to
   determine what is the downstream CDN (dCDN) to which the request is
   to be redirected.  This CDN selection decision can take into account
   various criteria such as administrative preferences (for example
   based on the commercial arrangements between the uCDN and candidate
   dCDNs including associated request handling costs) and/or such as
   whether candidate CDNs are have caches that are topologically close
   to the user and capable of handling that request.  Therefore, as
   discussed in section "Dynamic Footprint Discovery" of
   [I-D.davie-cdni-framework], there are situations where being able to
   dynamically discover the set of requests that a given dCDN is willing
   and able to serve is beneficial.  As also discussed in
   [I-D.davie-cdni-framework], this information could be potentially
   provided by the dCDN in response to a query by the uCDN, or the
   information (or its changes) could be spontaneously advertised by the
   dCDN.

   The proposal outlined in this document makes use of Multiprotocol-BGP
   (MP-BGP [RFC4760]) in order for CDNs and/or ISPs to advertise their
   footprint information as well as for CDNs to advertise their
   connectivity to these footprints.  In addition CDNs use MP-BGP
   advertisements to represent their interconnectivity.


2.  Terminology

   The following terminology is used in this document:

      CDNI Mesh: the set of CDNs participating into CDNI and using MP-
      BGP sessions between them in accordance with the approach defined
      in this document.  A CDNI Mesh has no requirements in terms of
      topology, i.e.: the mesh can be partial, full or hierarchical.





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      Footprint (FP): The exhaustive set of Prefixes a CDN is willing to
      serve.

      Footprint Element (FPE): Arbitrary set of prefixes with
      attributes.  They can be implicit (inferred from BGP) or explicit
      (advertised).

      Implicit Footprint Element Advertisement (FPE Implicit
      Advertisement): Footprint Element information derived from the BGP
      database.

      Footprint Element Advertisement (FPE-Adv): MP-BGP Message used by
      a CDN in order to advertise or withdrawn Footprint Elements and
      their attributes.

      Footprint Reachability Advertisement (FPR-Adv): MP-BGP Message
      used by a CDN in order to advertise or withdrawn Footprint
      reachability information.

      Capability Advertisement (CAP-Adv): MP-BGP Message used by a CDN
      in order to advertise or withdrawn capability information.


3.  CDNI Mesh and MP-BGP

   CDNI enables CDNs to communicate in order to deliver content in a
   collaborative mode.

   CDNI Mesh will make use of Multiprotocol-BGP (MP-BGP [RFC4760]) for
   the exchange of footprint, reachability and capability information.

   We define a new Sub Address Family (CDNI-SAFI, TBD) for Address
   Families (AF) 1 (IPv4) and 2 (IPv6) and a set of new Network Layer
   Reachability Information (NLRI) that will carry either FPE, FPR or
   CAP advertisements.  The NLRI will have a NLRI type determining the
   content (i.e.: FPE, FPR or CAP) so to distinguish advertisements.

   The advantage of using a separate address family is to isolate CDNI
   information from regular BGP-4 Internet information so to not
   compromise in any way the security and reliability of the current BGP
   information exchange used for IP network layer routing.

   The advantage of having separate FPE, FPR and CAP information is that
   a CDN needs not originate (and update) FPE information each time
   there's a change in the way a CDN is connected to other CDNs.  E.g.:
   if the complete Footprint information was to be exchanged between
   CDNs, it would consist of a very large amount of prefixes advertised
   (and re-advertised) each time a CDNI interconnection changes in the



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   CDNI Mesh.

   When an existing CDNI connection is removed or when a new connection
   between two CDNs is established, the only advertisements that need to
   be updated are the ones concerning the FPR.

   While footprint information is expected to be relatively stable, the
   CDNI Mesh (i.e.: the connectivity between CDNs) and the reachability
   from CDN to footprints may be impacted by network events.  Also, the
   connectivity between CDNs may be affected by the CDN selection policy
   which may be modified relatively frequently.

   CDNI FPR advertisements allow the CDNI Mesh to scale by adapting
   easily to topology changes.  In fact, just a few number of FPR
   advertisements are used by each CDN which makes the CDNI MP-BGP
   scheme very scalable.


4.  CDNI Information

   CDNI Information includes:

      Footprint (FP).

      Footprint Element (FPE).

      Footprint Reachability (FPR).

      CDN Capabilities (CAP).

4.1.  Footprint

   Footprint represents the exhaustive set of prefixes a CDN is willing
   to serve.  The set of prefixes may belong to one or more Autonomous
   Systems or may include subset of prefixes of one or more Autonomous
   Systems.  In other words, there is no strict relationship between an
   Autonomous System and the CDN Footprint.

   Example: if CDN-A delivers content to ISP-A users, then CDN-A
   footprint consists of all prefixes owned and connected to ISP-A.

4.2.  Footprint Elements (FPE)

   Footprint Elements refers to an arbitrary set of prefixes part of a
   CDN Footprint.

   FPEs can be inferred from the BGP-4 Internet database.  It is assumed
   that the CDN will have a BGP-4 feed with Internet prefixes that are



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   necessary in order for the CDNI Mesh to operate and from which it
   will be able to derive FPEs.

   The CDN will maintain a FPE Database that is isolated from the
   regular BGP Internet database.  The CDNI FPE database uses the CDNI-
   SAFI (TBD) MP-BGP address family.

   FPEs can be implicit (inferred from BGP) or explicit (advertised).

   Example 1: if CDN-A is willing to serve Autonomous System A and
   Autonomous System B users, then two footprints elements will be
   inferred from the BGP database in all CDNs: FPE-ASA and FPE-ASB.
   Then, CDN-A will advertise its reachability to FPEs FPE-ASA and FPE-
   ASB.  In this example FPEs are inferred by all CDNs by just looking
   at the BGP-4 Internet Database.

   Example 2: if CDN-B is willing to serve Autonomous System A users and
   a subset of Autonomous System B users, then CDN-B Footprint consist
   of two FPEs: Autonomous System A and the set of prefixes representing
   the subset of Autonomous System B users.  Autonomous System 'A' FPE
   is inferred from BGP-4 Database while the subset of Autonomous System
   B users is an FPE that will be explicitly advertised by CDN-B to the
   CDNI Mesh.

   The CDNI FPE Database includes FPEs inferred from the BGP-4
   (Internet) database as well as FPE Advertisements originated by the
   CDN and/or received from other CDNI Mesh members.

4.3.  Footprint Reachability (FPR)

   Footprint Reachability refers to the way a CDN can reach to one or
   more FPEs.  FPR consists of advertisements originated by each CDN for
   each of its FPE and advertised to the CDNI Mesh (through MP-BGP
   Messages).

   FPR Information is stored in the CDNI FPR Database which contains the
   information originated by the CDN and the information received from
   the other CDNs in the CDNI Mesh.

4.4.  CDN Capability Information (CAP)

   Each CDN advertises to the CDNI Mesh the set of its capabilities.
   The CDN originates a CDN Capabilities message (CAP) message
   containing the attributes describing such capabilities.

   Each CDN MUST originate a Capabilities message and each CDN will
   store in the CDNI Capabilities Database the set of Capabilities
   messages received from other members of the CDNI Mesh.



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5.  CDNI Functional Components

   This section describes the CDNI functional components (databases,
   messages, information sets) stored and exchanged between CDNs and
   related to CDN Footprints and Capabilities.  This document proposes
   the use of Multiprotocol-BGP for exchanging the CDNI information.
   The details of MP-BGP encodings are described in Section 7.

5.1.  CDNI Databases

   This section describes the set of databases defined for the
   propagation of Fooptrint and Capability information across the CDNI
   Mesh.  The goal of this section is to explain the different
   information elements that are required in order to properly determine
   FPE, FPR and CAP information.  This section is not to be intended as
   an implenentation description.  An implementation may combine or
   merge all data into single or multiple databases.

      CDNI Footprint Elements Database contains FPEs that are either
      derived from BGP-4 Internet table or received from other CDN
      through CDNI Footprint Elements Advertisements.

      CDNI Footprint Reachability Database contains the advertisements
      originated by the CDN and received from other CDNs and that
      describe how each CDN can reach its Footprint Elements.

      CDNI Capability Database contains the set of CDN capabilities
      advertised by each CDN.

5.1.1.  CDNI Footprint Elements Database

   FPE Database contains the FPEs that a CDN has inferred from the BGP-4
   Internet database as well as FPEs that have been explicitly
   advertised by other CDNs.

   FPE Database includes prefixes and their attributes as known in the
   BGP-4 Internet Database (e.g.: prefix, AS_PATH, MED, Communities,
   etc) in addition to CDNI specific attributes that are defined in
   following sections.

   FPE Database also contains the FPEs that have been explicitly
   advertised by remote CDNs.

   It is expected that for most of CDNs, the majority of the FPE
   information is inferred from BGP-4 Internet Database so to reduce
   significantly the advertisement of FPEs.





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5.1.2.  CDNI Footprint Reachability Database

   FPR Database contains the set of FPEs each CDN claimed reachability
   to.  This includes:

      The set of FPEs this CDN can reach.

      The set of FPEs other CDNs have advertised their reachability to.

   The FPR Database is populated by the FPR Advertisement messages
   originated and sent by each CDN participating into the CDNI Mesh.

5.1.3.  CDNI Capability Database

   Capability (CAP) Database contains the set of capabilities advertised
   by each CDN.

   The CAP Database is populated by the CAP Advertisement messages
   originated and sent by each CDN participating into the CDNI Mesh.

5.2.  CDNI MP-BGP Messages

   We define three new MP-BGP messages for the advertisement of CDNI
   Address Familiy NLRIs:

      Footprint Element Advertisement (FPE Advertisement) describing an
      FPEs and its attributes.

      Footprint Reachability Advertisement (FPR Advertisement)
      describing how a CDN can reach one or more FPEs.

      Capability Advertisement (CAP Advertisement) describing CDN
      capabilities.

   The propagation of CDNI Messages throughout the CDNI Mesh is done
   according to standard BGP rules and the inter-CDN connectivity will
   be reflected in the BGP attributes, e.g.: AS_PATH will describe the
   different CDNs the advertisement traversed during its propagation in
   the CDNI Mesh thus describing the inter-CDN connectivity.

5.2.1.  CDNI MP-BGP Footprint Element Advertisement

   FPE Advertisement is originated by a CDN willing to group prefixes it
   can reach under a unique identifier (identifying the FPE).  The
   message is originated and sent out by the CDN and propagated
   throughout the CDNI Mesh according to MP-BGP propagation rules.

   The FPE Advertisement includes CDNI NLRI, representing the FPE



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   address space, and attributes among which the identifier of the FPE.

5.2.2.  CDNI MP-BGP Footprint Reachability Advertisement

   In the CDNI Mesh, each CDN MUST advertise the different Footprint
   Elements it reaches.  The CDN maintains a FPE Reachability Database
   with entries describing its connectivity to Footprints Elements.

   The propagation of CDN Connectivity advertisements throughout the
   CDNI Mesh is done according to standard BGP rules and the inter-CDN
   connectivity will be reflected in the BGP attributes (e.g.: AS_PATH
   will describe the different CDNs the advertisement traversed during
   its propagation in the CDNI Mesh thus describing the inter-CDN
   connectivity).

5.2.3.  CDNI Capability Advertisement

   Each CDN MUST advertise information describing its capabilities.
   This is done in the CAP dvertisement message.

5.3.  CDNI Information Elements (Attributes)

   This section describes the different information elements contained
   in the CDNI Databases.

5.3.1.  CDN Identifier

   CDN_Identifier uniquely identifies the CDN within the CDNI Mesh.  CDN
   Identifier is exchanged inside the CDNI (MP-BGP) messages between
   CDNs.

5.3.2.  Footprint Element Identifier

   The role of the Footprint Element Identifier is to group all prefixes
   part of the same FPE under a unique identifier.  This allows a CDN to
   claim reachability to the FPE by just specifying the FPE Identifier
   rather than each individual prefix of the footprint.

   When inferring the CDNI footprint information from the regular BGP-4
   Internet database, the FPE Identifier is derived from the first ASN
   in the AS_PATH of the prefix, i.e.: the AS of origin of the prefix.

   FPE Identifiers are present in both FPE Advertisement and FPR
   Advertisement.  In the FPE Advertisement it is used to arbitrarily
   group prefixes under the same Identifier while in the FPR
   Advertisement, the FPE Identifier is used in order to describe which
   FPEs a CDN can reach.




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5.3.3.  Reachable Footprint Element

   Reachable FPE contains the FPE Identifier of each FPE the CDN claim
   reachability to.  Multiple instances of Reachable FPE are allowed in
   the same FPR Advertisement message.  FPE Identifier is assigned to
   the FPE by the CDN advertising the FPE (in the FPE Advertisement
   Message).  FPE Identifier contains an AS number when the FPE has been
   inferred from the BGP database.

5.3.4.  Origin_AS_PATH

   This attribute contains the prefix AS_PATH value that is present in
   the BGP-4 Internet Database of the CDN originating the FPR
   advertisement.

   Origin_AS_PATH aims to describe how the CDN can reach a given FPE and
   is present only in FPR advertisements.

5.3.5.  CDN Capabilities

   Capabilities are expressed in a set of attributes the CDN inserts in
   the Capability Advertisement message.

5.4.  CDNI MP-BGP NLRIs

   We define three types of CDNI NLRI: FPE-NLRI, FPR-NLRI and CAP-NLRI

   When referred to FPE, the NLRI contains either an IPv4 or IPv6
   prefix.

   In some cases, a given FPE prefix is reachable by multiple CDNs.  MP-
   BGP, according to BGP selection rule, will allow to select only one
   FPE and therefore information about FPE being multi-reachability
   through different CDNs may be lost.  In order to prevent this, the
   CDNI NLRI contains a CDNI FPE Distinguisher so to make two identical
   prefixes different from a BGP selection perspective.  The behavior is
   similar to what defined in [RFC4364].

   FPR NLRI consists of one or more FPE-Identifiers representing the
   FPEs the CDN can reach.

   CAP-NLRI contains a IPv4 or IPv6 prefix (called the CAP-Prefix)
   beloning to the CDN address space originating the CAP Advertisement
   Message.  Capabilities will be avertised using attributes to the CAP-
   prefix.






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6.  CDNI Example

   This section illustrates an example of CDNI Mesh with the set of
   databases and messages that are exchanged between CDNs.

6.1.  Topology

   The following topology is used:
                              CDN2    CDN3                       uCDN
       1.1.1.0/24 |--AS100---AS200---AS300---AS400---Internet---AS500
       2.2.2.0/24 |    |-----------------|      |
       3.3.3.0/24      |                        |
                       |------------------------|

      CDN2, CDN3 and uCDN participate into the CDNI Mesh.

      CDNI Mesh includes following MP-BGP Sessions: CDN2-CDN3 and CDN3-
      uCDN.  Note that there's no MP-BGP session between CDN2 and uCDN.

      AS100 and AS400 have no CDN.

      AS100 advertises all prefixes to AS300 and AS400.

      AS100 advertises only prefix 1.1.1.0/24 and 3.3.3.0/24 to AS200.

6.2.  CDN2 Footprint Element Advertisements

   CDN2 originates following Footprint Elements Advertisements:























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         Prefix CDN2:1.1.1.0/24
            AS_PATH: {CDN2}
            Footprint-Element Identifier: FP-CDN2

         Prefix CDN2:3.3.3.0/24
            AS_PATH: {CDN2}
            Footprint-Element Identifier: FP-CDN2

     where:

         Prefix CDN2:1.1.1.0/24 and Prefix CDN2:3.3.3.0/24 are the
            two prefixes advertised with the CDNI FPE Distinguisher
            corresponding to CDN2. The CDNI FPE Distinguisher is
            required so to distinguish between possible identical
            prefixes advertised by other CDNs.

         AS_PATH contains the set of CDNs the update has traversed.
            It is mainly used for loop prevention in BGP in the CDNI
            Mesh.

            Note: the AS numbers in the AS_PATH represent the CDNs,
                  not the BGP autonomous systems.

         Footprint-Element Identifier contains the identifier of
            the Footprint-Element and it is used by CDN2 when
            originating the Footprint Reachability Advertisement.

   Note that uCDN and CDN3 do NOT originate any Footprint Element
   Message.

6.3.  Footprint Element Database in each CDN

   Footprint Elements Database in constructed by inferring all info from
   BGP database plus the Footprint Elements Advertisements received from
   within the CDNI Mesh.

   In CDN2 the Footprint Elements Database is as follows:
          1.1.1.0/24; AS_PATH: {100}         ===\
          2.2.2.0/24; AS_PATH: {300, 100}    ====> inferred from
          3.3.3.0/24; AS_PATH: {100}         ===/   BGP table

          CDN2:1.1.1.0/24
            AS_PATH: {}
            Footprint-Element Identifier: FP-CDN2

          CDN2:3.3.3.0/24
            AS_PATH: {}
            Footprint-Element Identifier: FP-CDN2



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   In CDN3 the Footprint Elements Database is as follows:
          1.1.1.0/24; AS_PATH: {100}         ===\
          2.2.2.0/24; AS_PATH: {100}         ====> inferred from
          3.3.3.0/24; AS_PATH: {100}         ===/    BGP table

          CDN2:1.1.1.0/24
            AS_PATH: {CDN2}
            Footprint-Elements Identifier: FP-CDN2

          CDN2:3.3.3.0/24
            AS_PATH: {CDN2}
            Footprint-Element Identifier: FP-CDN2

   In uCDN the Footprint Elements Database is as follows:
          1.1.1.0/24; AS_PATH: {<internet>, 400, 100} ===\  inferred
          2.2.2.0/24; AS_PATH: {<internet>, 400, 100} ====>   from
          3.3.3.0/24; AS_PATH: {<internet>, 400, 100} ===/  BGP table

         CDN2:1.1.1.0/24
           AS_PATH: {CDN3, CDN2}
           Footprint-Element Identifier: FP-CDN2

         CDN2:3.3.3.0/24
           AS_PATH: {CDN3, CDN2}
           Footprint-Element Identifier: FP-CDN2

   The Footprint-Elements Database contains prefixes inferred from the
   BGP database and the prefixes received through Footprint-Element
   Advertisements.

   Footprint-Element prefixes derived from BGP database do not require a
   CDNI FPE Distinguisher.The way an implementation stores inferred FPE
   information (with or without CDNI FPE Distinguisher is out of the
   scope of this document.

   The prefixes received by FPE Advertisements need a CDNI FPE
   Distinguisher because multiple CDNs may advertise the same set of
   prefixes and we need to preserve all from selection rules.

6.4.  Footprint Reachability Advertisements

   Each CDN will advertise its reachability to Footprint Elements:

   CDN2 Footprint Reachability Advertisement:







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          CDN-Identifier: CDN2
          AS_PATH: <will contain the AS_PATH representing the path
                    taken by Footprint-Reachability advertisement in
                    the CDNI Mesh>

          Reachable Footprint-Element: AS200
          Origin_AS_PATH: {}

          Reachable Footprint-Element: FP-CDN2
          Origin_AS_PATH: {100}

          Where:

          Origin_AS_PATH describes the BGP AS_PATHs as known in CDN2.

   CDN2 advertises reachability to two sets of prefixes: one consists of
   all prefixes in AS200 and another set consists of prefixes he
   received from AS100 (and that he previously sent with Footprint-
   Element Advertisements).

   CDN3 Footprint Reachability Advertisement:
          CDN-Identifier: CDN3
          AS_PATH: <will contain the AS_PATH representing the path
                    taken by Footprint-Reachability advertisement in
                    the CDNI Mesh>

          Reachable Footprint-Element: AS300
          Origin_AS_PATH: {}

          Reachable Footprint-Element: AS100
          Origin_AS_PATH: {200, 100}

          Where:

          Origin_AS_PATH describes the BGP AS_PATHs as known in CDN3.

   CDN3 advertises reachability to two sets of prefixes: AS100 and
   AS300.

   Each CDN advertises:

      CDNI Identifier.

      Set of reachable Footprint-Elements (i.e.: a set of FPE
      Identifiers) with their corresponding Origin_AS_PATH.

      The AS_PATH representing the BGP connectivity within the CDNI
      Mesh.



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6.5.  Capability Advertisements

   Each CDN originates a CAP Advertisement messages carrying information
   about its capabilities.  Each CDN will advertise:

      A prefix owned by the CDN (i.e.: part of the CDN address space).

      Its CDN Identifier.

      A set of attributes describing the CDN capabilities (encoded as
      BGP Extended Community Attributes).

   CDN2 Capability Advertisement:
          CDN-Identifier: CDN2
          Communities (std/ext): representing CDN2 capabilities
          AS_PATH: <will contain the AS_PATH representing the path
                    taken by Footprint-Reachability advertisement in
                    the CDNI Mesh>
          NLRI: CDN2-Prefix

   CDN3 Capability Advertisement:
          CDN-Identifier: CDN3
          Communities (std/ext): representing CDN capabilities
          AS_PATH: <will contain the AS_PATH representing the path
                    taken by Footprint-Reachability advertisement in
                    the CDNI Mesh>
          NLRI: CDN3-Prefix

6.6.  FPE, FPR and CAP Databases in uCDN

   uCDN has the two following databases:

      Footprint-Elements Database:
          1.1.1.0/24
              AS_PATH: {<internet>, 400, 100} ==\
          2.2.2.0/24                          ===\
              AS_PATH: {<internet>, 400, 100} ====> inferred from
          3.3.3.0/24                          ===/    BGP table
              AS_PATH: {<internet>, 400, 100} ==/

          CDN2:1.1.1.0/24
              AS_PATH: {CDN3, CDN2}
              Footprint-Element Identifier: FP-CDN2
          CDN2:3.3.3.0/24
              AS_PATH: {CDN3, CDN2}
              Footprint-Element Identifier: FP-CDN2





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      Footprint-Reachability Database:
          CDN-Identifier: CDN2
              AS-PATH: {300, 200}

              Reachable Footprint-Element: AS200
              Origin_AS_PATH: {}

              Reachable Footprint-Element: FP-CDN2
              Origin_AS_PATH: {100}

          CDN-Identifier: CDN3
              AS-PATH: {300}

              Reachable Footprint-Element: AS300
              Origin_AS_PATH: {}

              Reachable Footprint-Element: AS100
              Origin_AS_PATH: {200, 100}

      Capability Database:
   CDN-Identifier: CDN2
          Communities (std/ext): representing CDN2 capabilities
          AS_PATH: <will contain the AS_PATH representing the path
                    taken by Footprint-Reachability advertisement in
                    the CDNI Mesh>
          NLRI: CDN2-Prefix

   CDN-Identifier: CDN3
          Communities (std/ext): representing CDN capabilities
          AS_PATH: <will contain the AS_PATH representing the path
                    taken by Footprint-Reachability advertisement in
                    the CDNI Mesh>
          NLRI: CDN3-Prefix

   The Footprint-Reachability and Capabilities databases also contains
   the AS_PATH representing the MP-BGP connectivity in the CDNI Mesh and
   the path taken by Footprint-Reachability Advertisements.  It is
   anyway mandatory in BGP for message loop prevention.

6.7.  Request Routing for user 2.2.2.2

   The following workflow is used for a request coming from user
   2.2.2.2:

      User with address 2.2.2.2 sends a content request to uCDN.

      uCDN does a lookup in Footprint-Elements Database for address
      2.2.2.2 and finds following entry:



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         2.2.2.0/24
              AS_PATH: {<internet>, 400, 100}

      uCDN does a lookup in Footprint-Reachability Database and look for
      a CDN claiming connectivity to AS100.  It finds following entry:
          CDN-Identifier: CDN3
              AS-PATH: {300}

              Reachable Footprint-Element: AS300
              Origin_AS_PATH: {}

              Reachable Footprint-Element: AS100
              Origin_AS_PATH: {200, 100}

      uCDN can select CDN3 as downstream CDN.

6.8.  Request Routing for user 1.1.1.1

   The following workflow is used for a request coming from user
   1.1.1.1:

      User with address 1.1.1.1 sends a content request to uCDN.

      uCDN does a lookup in Footprint-Elements Database for address
      1.1.1.1 and finds following entries:
          1.1.1.0/24
              AS_PATH: {<internet>, 400, 100}

       and

          CDN2:1.1.1.0/24
              AS_PATH: {CDN3, CDN2}
              Footprint-Element Identifier: FP-CDN2

      uCDN prefers the entry originated by a Footprint-Element
      Advertisement and looks into the Footprint-Reachability Database
      for a CDN claiming connectivity to Footprint-Element Identifier:
      FP-CDN2.  It finds following entries:
          CDN-Identifier: CDN2
              AS-PATH: {300, 200}

              Reachable Footprint-Element: AS200
              Origin_AS_PATH: {}

              Reachable Footprint-Element: FP-CDN2
              Origin_AS_PATH: {100}





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      uCDN can select CDN2 as downstream CDN


7.  CDNI MP-BGP Encodings

   This section describes the CDNI MP-BGP messages with their attributes
   and NLRI encodings details.

7.1.  CDNI Attributes

   CDNI uses standard BGP attributes in both FPE and FPR advertisements
   in addition to the following newly defined attributes:

      FPE_Identifier is present in FPE advertisements (when identifying
      an FPE as a set of prefixes) and FPR advertisements (when
      identifying a reachable FPE).

      CDN_Identifier is present in both FPE and FPR advertisements).

      Origin_AS_PATH is present in FPR advertisements.

      CDN Capabilities is present in CAP advertisements.

7.1.1.  CDNI Identifier

   CDN_Identifier is a mandatory transitive attribute consisting of an
   extended community (type TBD) uniquely identifying the CDN within the
   CDNI Mesh.  CDNI_Identifier must be unique within the CDNI Mesh.  The
   recommended method is to use (as for the FPE_Identifier) the AS or IP
   Address format as described in[RFC4360].

7.1.2.  FPE Identifier

   FPE Identifier is a mandatory and transitive attribute consisting of
   an extended community (type TBD) containing a Footprint Element
   identifier.  The FPE_Identifier uniquely identifies the FPE within
   the CDNI Mesh.  The format of the FPE_Identifier encodings should
   ensure uniqueness of values.  The recommended method for encoding
   FPE_Identifier is to use the format as defined in RFC4360 and use
   either the AS or an IP address owned by the CDN.  This method, and
   the extended community format, allows a CDN to create multiple unique
   FPE_Identifiers.

7.1.3.  Origin_AS_PATH

   Origin_AS_PATH is an optional transitive attribute having the same
   format as AS_PATH attribute and containing the AS_PATH value of the
   Footprint Element known in the CDN originating the FPR advertisement.



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   Origin_AS_PATH must be left unchanged and has the same format as
   AS_PATH BGP attribute as defined in [RFC4271].

7.1.4.  Capabilities

   Capabilities is a mandatory and transitive attribute consisting of an
   extended community (type TBD) containing a value representing a given
   capability (TBD).  More than one Capability attribute is allowed so
   to allow a CDN to advertise multiple capabilities in the same
   message.  The encodings of Extended Communities is defined in:
   [RFC4360].

7.2.  CDNI Messages

   Three messages are used: FPE Advertisement, FPR Advertisement and CAP
   Advertisement.

7.2.1.  FPE Advertisement

   Footprint Element Advertisement message is used by a CDN in order to
   advertise a Footprint Element that can't be inferred from the BGP-4
   Internet Database and that needs explicit advertisement.

   The FPE Advertisement consists of one or more prefixes that a CDN
   reaches.  The FPE Advertisement scope is not to describe how the CDN
   can reach the FPE but rather what are the prefixes forming the FPE.
   The FPE Advertisement message should contain following information:

      CDN_Identifier: uniquely identifies the CDN originating the
      message.  It is mandatory and transitive attribute.
      CDN_Identifier format is described in Section 7.1.

      Footprint-Element Identifier: a number uniquely identifying the
      FPE as defined in Section 7.1.  FPE-Identifier is encoded as an
      extended community.  It is mandatory and transitive.

      Standard BGP attributes such as AS_PATH, Communities,
      Local_Preference, MED, etc. are also used in the FPE Advertisement
      Messages.

      NLRI: the set of prefixes (address and mask) of the FPE.

      A CDNI Distinguisher is prependd to each prefix of the FPE.  The
      CDNI Distingsuiher allows multiple CDNs to advertise the same
      prefix in their FPE Advertisement.  Each CDN must use a unique
      number.  The recommended method for assigning RDs is to use the
      CDN AS number or an IP address owned by the CDN.




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7.2.2.  FPR Advertisement

   Footprint Reachability Advertisement message is used by a CDN willing
   to advertise the FPEs it can reach.  The FPR Advertisement consists
   of a set of FPE-Identifiers and their attributes.  Following
   information should be present in the FPR Advertisement message:

      CDN_Identifier: uniquely identifies the CDN originating the
      message.  It is mandatory and transitive attribute.
      CDN_Identifier format is described in Section 7.1.

      Reachable Footprint-Element: one or more AS numbers and/or
      FPE_Identifier representing the reachable FPEs.  Reachable_FPE is
      encoded as a set of extended communities.  At least one must be
      present in the message and the attribute is transitive.  FPEs that
      have been inferred from the BGP4 Internet database are identified
      through their AS number and FPEs that have been explicitly
      advertised are identified by their FPE_Identifier.

      Standard BGP attributes such as AS_PATH, Communities,
      Local_Preference, MED, etc. are also used in the FPR Advertisement
      Messages.

      Origin_AS_PATH.  This attribute is related to an FPE and contains
      the value of the BGP AS_PATH of the FPE in the CDN originating the
      FPR message.  When used, it implies all prefixes of the same FPE
      share the same BGP AS_PATH in the CDN originating the FPR message.

      NLRI: Reachable Footprint-Element: one or more FPE Identifiers
      representing the reachable FPEs.  Reachable FPE is encoded in the
      CDNI NLRI.  At least one must be present in the message.  FPEs
      that have been inferred from the BGP4 Internet database are
      identified through their AS number and FPEs that have been
      explicitly advertised are identified by their FPE Identifier.

7.2.3.  CAP Advertisement

   Capability Advertisement message is used by a CDN in order to
   advertise its capabilities.  Capabilities are encoded as a set of BGP
   Extended Communities.  The CAP Advertisement Message contains:

      A CDN_Identifier: uniquely identifies the CDN originating the
      message.  It is mandatory and transitive attribute.
      CDN_Identifier format is described in Section 7.1.

      One or more Extended Communities attributes describing
      capabilities.




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      Standard BGP attributes such as AS_PATH, Communities,
      Local_Preference, MED, etc. are also used in the CAP Advertisement
      Messages for policy reasons.

      A CDN Prefix: a NLRI encoded prefix (IPv4 or IPv6) owned by the
      CDN (i.e.: a prefix that is part of the address space of the CDN).

7.3.  CDNI NLRI

   Multiprotocol-BGP defines two attributes, MP_REACH and MP_UNREACH,
   that are BGP's containers for carrying opaque information.  Each CDNI
   NLRI describes either a FPE or a FPR.

   All FPE and FPR information SHALL be encoded using AFI 1 or 2 (ipv4
   or ipv6) with a TBD (CDNI) SAFI.

   In order for two BGP speakers to exchange CDNI NLRI, they MUST use
   BGP Capabilities Advertisement to ensure that they both are capable
   of properly processing CDNI NLRI.  This is done as specified in
   [RFC4760], by using capability code 1 (multi-protocol BGP), with the
   AFI: 1 or 2, SAFI: TBD.

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            NLRI Type          |     Total NLRI Length         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                       CDNI NLRI (variable)                    |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       where:
       NLRI Type: 1 (FPE)
                  2 (FPR)
                  3 (CAP)

7.3.1.  CDNI-NLRI Type 1: FPE Advertisement













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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        NLRI Type: 1           |     Total NLRI Length         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       +                   CDNI FPE Distinguisher                      +
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                   IPv4/IPv6 NLRI (variable)                   |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       where:
       NLRI Type: 1 specifies the FPE Advertisement
       CDNI FPE Distinguisher: 8 octets
       NLRI: IPv4 or IPv6 prefix

7.3.2.  CDNI-NLRI Type 2: FPR Advertisement


        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        NLRI Type: 2           |     Total NLRI Length         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       +                       Connected FPEs (variable)               +
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       where:
       NLRI Type 2 specifies the FPR Advertisement
       Connected FPEs: set of FPE Identifiers representing the FPEs the
                       CDN can reach.

7.3.3.  CDNI-NLRI Type 3: CAP Advertisement













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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        NLRI Type: 3           |     Total NLRI Length         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       +                       IPv4/IPv6 NLRI                          +
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       where:
       NLRI Type 3 specifies the CAP Advertisement
       NLRI: IPv4 or IPv6 prefix

7.3.4.  NLRI Encoding

   The Network Layer Reachability Information contains one or more IPv4
   or IPv6 prefixes, according to AFI value, and is encoded as one or
   more 2-tuples of the form <length, prefix>, whose fields are
   described below:
                   +---------------------------+
                   |   Length (1 octet)        |
                   +---------------------------+
                   |   Prefix (variable)       |
                   +---------------------------+

       where:
       Length: the Length field indicates the length in bits of the IP
       address prefix.  A length of zero indicates a prefix that matches
       all IP addresses (with prefix, itself, of zero octets).

       Prefix: the Prefix field contains an IP address prefix, followed
       by enough trailing bits to make the end of the field fall on an
       octet boundary.  Note that the value of the trailing bits is
       irrelevant.

   In the FPE Advertisement message, the NLRI contains the set of
   prefixes part of the FPE to be advertised.

   In the CAP Advertisement message, the NLRI contains a prefix ownded
   by the CDN.

   It has to be noted that a CDN may use multiple FPR messages for
   advertising reachability to multiple FPEs.  In such cases multiple
   NLRI prefixes would be needed in order not to create collisions in
   the BGP selection process (that would select only one NLRI message
   among the ones having identical NLRI prefixes).




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8.  Compliance with CDNI Requirements

   [I-D.ietf-cdni-requirements] outlines the requirements for the
   solution and interfaces to be specified by the CDNI working group.
   This section identifies the relevant requirements from that document
   and discusses compliance by the solution proposed in this document.

   [Editor's Note: Text is to be added when requirements-03 is
   available.  This needs to discuss the requirements labeled R27, R28,
   R29 and R30 as of requirements-02].


9.  IANA Considerations

   none.


10.  Security Considerations

   This draft does not affect the BGP security model.


11.  Acknowledgements

   The authors would like to thank Steven Luong, Manish Bhardwaj and
   Bruce Davie for their contributions.


12.  References

12.1.  Normative References

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

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, February 2006.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, February 2006.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              January 2007.




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12.2.  Informative References

   [I-D.bertrand-cdni-use-cases]
              Bertrand, G., Stephan, E., Watson, G., Burbridge, T.,
              Eardley, P., and K. Ma, "Use Cases for Content Delivery
              Network Interconnection", draft-bertrand-cdni-use-cases-02
              (work in progress), July 2011.

   [I-D.davie-cdni-framework]
              Davie, B. and L. Peterson, "Framework for CDN
              Interconnection", draft-davie-cdni-framework-01 (work in
              progress), October 2011.

   [I-D.ietf-cdni-requirements]
              Leung, K. and Y. Lee, "Content Distribution Network
              Interconnection (CDNI) Requirements",
              draft-ietf-cdni-requirements-03 (work in progress),
              June 2012.

   [I-D.jenkins-cdni-problem-statement]
              Niven-Jenkins, B., Faucheur, F., and N. Bitar, "Content
              Distribution Network Interconnection (CDNI) Problem
              Statement", draft-jenkins-cdni-problem-statement-02 (work
              in progress), March 2011.


Authors' Addresses

   Stefano Previdi (editor)
   Cisco Systems, Inc.
   Via Del Serafico 200
   Rome  00191
   IT

   Email: sprevidi@cisco.com


   Francois Le Faucheur
   Cisco Systems, Inc.
   Greenside, 400 Avenue de Roumanille
   Sophia Antipolis  06410
   FR

   Email: flefauch@cisco.com







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   Jan Medved
   Cisco Systems, Inc.
   3700 Cisco Way
   SAN JOSE, CA  95134
   US

   Email: jmedved@cisco.com


   Allan Guillou
   SFR
   40-42 Quai du Point du Jour
   Boulogne-Billancourt  92659
   FR

   Email: allan.guillou@sfr.com



































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