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Versions: 00 01 02                                                      
CDNI WG                                                  S. Previdi, Ed.
Internet-Draft                                            F. Le Faucheur
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: April 26, 2012                                       A. Guillou
                                                                     SFR
                                                               J. Medved
                                                  Juniper Networks, Inc.
                                                        October 24, 2011


                      CDNI Footprint Advertisement
             draft-previdi-cdni-footprint-advertisement-00

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 April 26, 2012.

Copyright Notice

   Copyright (c) 2011 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



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   Provisions Relating to IETF Documents
   (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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  CDNI Mesh and MP-BGP . . . . . . . . . . . . . . . . . . . . .  3
   3.  CDNI Information . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Footprint Information  . . . . . . . . . . . . . . . . . .  5
     3.2.  Connectivity Information . . . . . . . . . . . . . . . . .  5
   4.  CDNI MP-BGP  . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  CDNI MP-BGP Footprint Information and Advertisements . . .  6
       4.1.1.  CDNI Footprint Attributes: Footprint Identifier  . . .  6
       4.1.2.  CDNI Footprint Attributes: Origin_AS_PATH  . . . . . .  7
       4.1.3.  Multihomed Prefixes  . . . . . . . . . . . . . . . . .  7
     4.2.  CDNI MP-BGP Connectivity Information and Advertisements  .  8
       4.2.1.  CDNI Connectivity Prefix . . . . . . . . . . . . . . .  8
       4.2.2.  CDNI Connectivity Attribute: Connected Footprints  . .  8
       4.2.3.  CDNI Connectivity Advertisement Attributes:
               Origin_AS_PATH . . . . . . . . . . . . . . . . . . . .  9
   5.  CDNI Topology Example  . . . . . . . . . . . . . . . . . . . .  9
   6.  CDNI MP-BGP Operations . . . . . . . . . . . . . . . . . . . . 10
     6.1.  Internal and External MP-BGP Sessions  . . . . . . . . . . 10
     6.2.  CDNI MP-BGP NLRI . . . . . . . . . . . . . . . . . . . . . 11
       6.2.1.  CDNI Footprint NLRI and Attributes . . . . . . . . . . 11
       6.2.2.  CDNI Connectivity NLRI and Attributes  . . . . . . . . 11
   7.  Example of CDNI Mesh . . . . . . . . . . . . . . . . . . . . . 12
     7.1.  CDNI Footprint Information and Advertisements  . . . . . . 13
     7.2.  Connectivity Information and Advertisements  . . . . . . . 15
   8.  Compliance with CDNI Requirements  . . . . . . . . . . . . . . 16
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 17
     12.2. Informative References . . . . . . . . . . . . . . . . . . 17
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17







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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.  CDNI Mesh and MP-BGP

   CDNI enables CDNs to communicate in order to deliver content in a
   collaborative mode.  In this document, we refer to a CDNI Mesh as 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.

   CDNI Mesh will make use of Multiprotocol-BGP (MP-BGP [RFC4760]) for



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   the exchange of footprint and connectivity information.

   We define a new Address Family (CDNI-AF, TBD) and a new NLRI that
   will carry either CDN Footprint or CDN Connectivity advertisements.
   The NLRI will have a NLRI type (i.e.: CDNI-footprint and CDNI-
   connectivity) so to distinguish footprint and connectivity
   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 footprint and connectivity
   information is that a CDN needs not originate (and update) footprint
   information each time there's a change in the way a CDN is connected
   to other CDNs.  E.g.: if all 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 CDNI Mesh.

   When an existing CDN 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 connectivity.

   While the footprint information is expected to be relatively stable,
   the CDN Mesh (i.e.: the connectivity between CDNs) and the
   connectivity between the CDN and the 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 Connectivity advertisements allow the CDNI Mesh to scale by
   adapting easily to topology changes.  In fact, just a few number of
   connectivity advertisements are used by each CDN which makes the CDNI
   MP-BGP scheme very scalable.


3.  CDNI Information

   The CDNI Information is of two types:

      Footprint Information, stored in the CDNI (MP-BGP) Footprint
      Database.

      Connectivity Information, stored in the CDNI (MP-BGP) Connectivity
      Information Database.




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3.1.  Footprint Information

   Footprint Information (FI).  The CDN Footprint Information refers to
   the set of prefixes (with all their BGP attributes) that the CDN is
   capable of, and willing to deliver content to in a given region and
   or in a given Autonomous System.  Note that a CDN may be capable and
   willing to serve content to more than one 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.

   Footprint Information is therefore inferred from the BGP-4 Internet
   database.  It is assumed that the CDN will have a BGP-4 feed with
   Internet prefixes that are necessary in order for the CDNI Mesh to
   operate and from which it will be able to derive the different
   footprints.

   The CDN will maintain a database with footprint information that is
   separate from the regular IP BGP database.  The CDNI footprint
   information database uses the CDNI-AF MP-BGP address family.

   In addition, a CDN may want to advertise to other CDNs part or all of
   its footprint information.  For example, a CDN may want to give a
   better granularity of the prefixes of its footprint (e.g.: longer
   masks) or may want to add more attributes (e.g.: communities and
   extended communities) to its footprint information.  Therefore the
   CDN is capable of originating Footprint Advertisements (from its CDNI
   Footprint Database) and send them to its neighbors of the CDNI-Mesh.

   The CDNI Footprint Information Database includes footprint
   information inferred by the BGP-4 (Internet) database as well as
   footprint information explicitely advertised by neighboring CDNs.

3.2.  Connectivity Information

   Connectivity Information refers to how the CDN is connected to a
   footprint (and to which footprints).  This information needs to be
   advertised by the CDN to the rest of the CDNI Mesh so that every CDN
   knows which CDN is connected to which footprints.

   It has to be noted that by "connectivity" we do not intend physical
   direct connectivity between the CDN and the footprint but rather the
   ability to deliver content to the footprint.  Connectivity
   Advertisements are sent through MP-BGP and using CDNI-AF
   advertisements.

   Connectivity Information is stored in the CDNI Connectivity Database
   which contains the information originated by the CDN and the



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   information received from the other CDNs in the CDNI Mesh.


4.  CDNI MP-BGP

   This section describes the CDNI Footprint and Connectivity
   Information in the CDNI MP-BGP databases.  Two databases are used:

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

      CDNI Connectivity Database that contains the advertisements made
      by each CDN describing how they are connected to footprints.

4.1.  CDNI MP-BGP Footprint Information and Advertisements

   Footprint information first comprises IP prefixes as known in the
   BGP-4 database and that need to be translated into the CDNI-AF format
   and stored in the CDNI Footprint database.  BGP-4 information is
   inserted in the CDNI Footprint database and all BGP attributes of
   each original route are preserved (e.g.: AS_PATH, MED, Communities,
   Extended Communities).  In addition, a CDN may add more attributes to
   the CDNI Footprint database routes.

   As discussed earlier, a CDN may want to explicitly advertise
   footprint information to the CDNI-Mesh (as explained in Section 3.1).
   When it does so, this information is also incorporated by the in its
   CDNI Footprint database by a CDN receiving these advertisments.
   However, it is expected that a CDN acquires most of the footprint
   information from the BGP-4 Internet table.  So we expect limited
   usage of footprint advertisements between CDNs.

   For example, a CDN (or ISP) may originate MP-BGP footprint
   advertisement including a Community attribute representing the
   location of the prefixes or the type of user connectivity (e.g.:
   fiber vs. cable vs. dsl vs Mobile3G vs Mobile 4G).  Alternatively,
   such information could be delivered initially by the ISP in the BGP-4
   database.

4.1.1.  CDNI Footprint Attributes: Footprint Identifier

   Footprints are associated to Autonomous Systems.  Therefore, the
   identifier of a footprint is its Autonomous System Number (ASN).
   When the CDN creates the CDNI Footprint database, it will assign to
   each prefix, a new (TBD) Extended Community carrying the Footprint
   Identifier.




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   Footprint Identifier is derived from the Autonomous System Number
   (ASN) of the original route.  When inferring the CDNI footprint
   information from the regular BGP-4 Internet database, the footprint
   identifier is derived from the first ASN in the AS_PATH of the
   prefix.

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

   Footprint Identifier may also be used in order to describe a finer
   granularity than the ASN.  Example: a CDN or an ISP participating
   into the CDNI Mesh, may want to originate footprint advertisement
   with a Footprint Identifier describing a region of its footprint
   (e.g.: an ISP may have multiple peering points in different locations
   and may want to partition its footprint so to represent geographical
   groups.)

   For that purpose multiple Footprint Identifiers are used (e.g.: a
   footprint representing Los Angeles area and another footprint
   representing New York City area).  These two footprints MUST be
   understood as part of the same ISP but representing different groups
   of prefixes.

   Using separate Footprint Identifiers (one for LA prefixes and one for
   NYC prefixes) allows the CDNI Mesh to handle the footprints
   separately even if they belong to the same ISP.  Footprint Identifier
   MUST be unique across the CDNI Mesh and therefore are numbered using
   the ISP AS numbers followed by additional bit space allowing more
   footprint identifiers per ISP.

4.1.2.  CDNI Footprint Attributes: Origin_AS_PATH

   A new MP-BGP attribute (TBD) is defined and called Origin_AS_PATH.
   This attribute contains the prefix AS_PATH value that is present on
   the CDNI footprint database.

   The Origin_AS_PATH is used when a CDN originates a CDNI Footprint
   Advertisement.  The AS_PATH of the new advertisement follows the BGP
   rules (i.e.: it is created with the CDN ASN and further updated at
   each AS hop) while the Origin_AS_PATH contains the AS_PATH of the
   original prefix.

4.1.3.  Multihomed Prefixes

   In some cases, a given prefix may be part of different footprint if
   it represents a customer connected to two separate ISPs.  In some



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   cases it is useful to preserve this information and allow both
   prefixes advertisements in the BGP database.  However, due to BGP
   Path Selection rules, when a BGP speaker receives two or more
   advertisements for the same prefix, it selects one and ignore the
   others.

   In order to prevent this to happen a Route Distinguisher may be used
   in the advertisement so that, from a BGP selection perspective, the
   prefix advertisements are not considered being equal.

4.2.  CDNI MP-BGP Connectivity Information and Advertisements

   Once footprint information is known in the CDNI Mesh, each CDN should
   advertise its connectivity to the footprints it has access to.  The
   CDN maintains a MP-BGP CDNI Connectivity Database with entries
   describing its connectivity to footprints.

4.2.1.  CDNI Connectivity Prefix

   When a CDN wants to advertise its footprint connectivity it
   originates a MP-BGP advertisement containing a prefix and a set of
   attributes.  The prefix it uses MUST be a prefix in the address space
   owned by the CDN.  A CDN willing to advertise different set of
   footprints connectivity may use different prefix advertisements each
   with its set of attributes.

   The Connectivity prefix(es) the CDN originates may contain any
   standard MP-BGP attribute and it MUST contain a newly defined
   attribute: Connected Footprints.

4.2.2.  CDNI Connectivity Attribute: Connected Footprints

   Connected Footprints attribute describes the set of Footprint
   Identifiers (FIs) the CDN claims connectivity to.

   The Connected Footprint attribute (CF) is a set of Footprint
   Identifiers which means a set of Extended Communities as defined in
   Section 4.1.1.

   The propagation of CDN Connectivity advertisements throughout the
   CDNI Mesh is done according to standard MP-BGP rules and the inter-
   CDN connectivity will be reflected in the MP-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).






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4.2.3.  CDNI Connectivity Advertisement Attributes: Origin_AS_PATH

   The CDNI Connectivity Advertisement contains a new (TBD) attribute
   called Origin_AS_PATH that contains the AS_PATH value describing the
   distance (expressed in AS Hop Count) between the CDN and the
   advertised connected footprint.

   This attribute will allow remote CDNs to understand how this CDN is
   distant (or close, in terms of AS hop count) to the footprint.

   The regular AS_PATH attribute of the Connectivity Advertisement is
   updated during its propagation in the CDNI Mesh so to prevent BGP
   message loops (according to BGP rules).


5.  CDNI Topology Example

   The figure below gives an example how CDNs collaborate and how they
   create their CDNI Footprint and Connectivity databases.

                    +-------------------------------------------+
                    |           CDNI (partial or full) Mesh     |
       /\           +-------------------------------------------+
       ||               |           |           |           |
       ||           +-------+   +-------+   +-------+   +-------+
   connectivity     | CDN 1 |   | CDN 2 |   | CDN 3 |   | CDN 4 |
   advertisements   +-------+   +-------+   +-------+   +-------+
                        |           |     ___/   \       /  |
   _____________________|___________|____/_______|_____/____|_____
                        |           |  /         |   /      |
       /\          +-------+   +-------+   +-------+   +-------+
       ||          | ASN 1 |   | ASN 2 |   | ASN 3 |   | ASN 4 |
       ||          +-------+   +-------+   +-------+   +-------+
   footprint           |           |           |           |
   advertisements  +-------------------------------------------+
                   |                Internet                   |
                   +-------------------------------------------+

            Figure 1: Footprint and Connectivity Advertisements

   In the figure above 4 CDNs are connected to a set of 4 different
   footprints.  Each CDN is capable of inferring the footprint
   information from the BGP-4 Internet table and will create a CDNI
   Footprint Database where a Footprint Identifier will be assigned to
   each prefix of the footprints.  The Footprint Identifier to each
   prefix will be assigned based on the ASN of the prefix.

   In addition, each CDN advertises its connectivity to the footprint.



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   All CDNI information (footprint and connectivity) is then known in
   the entire CDNI Mesh.


6.  CDNI MP-BGP Operations

   Connectivity advertisements and, when necessary, Footprint
   Advertisements consist of MP-BGP update messages CDNs advertise to
   the CDNI Mesh (following standard MP-BGP propagation rules).

   Footprint consists of prefixes known in the CDNI Footprint Database
   (MP-BGP).  CDNs advertises these prefixes and can use standard BGP
   attribute to attach more information to these prefixes.  In addition
   a new Extended Community Type is defined so to convey the Footprint
   Identifier that associate each prefix to a given footprint.

   Connectivity advertisements are originated using one or more prefixes
   the CDN will use in order to convey the description of its
   connectivity to a footprint.  The prefix has the solely purpose to
   convey the connectivity information of the CDN (i.e.: the prefix
   itself is not to be used for routing or selection purposes).  The
   footprint connectivity of a CDN is expressed in the Extended
   Community Attribute type "Connected Footprint" which consists of the
   set of Footprint Identifiers the CDN is connected/have access to.
   The Extended Community being additive, more than one Footprint
   Identifier is allowed in the CDN Connectivity advertisement.

   Also, the Origin_AS_PATH attribute reflects how the CDN is
   effectively distance/close to the footprint from a network layer
   perspective.

   MP-BGP sessions are established between CDNs.  MP-BGP requires an
   Autonomous System (AS) number that is unique across all CDNs.
   Therefore each CDN participating into the CDNI Mesh MUST have a
   unique AS number.

6.1.  Internal and External MP-BGP Sessions

   CDNs establish external MP-BGP sessions with each others.  The MP-BGP
   session has to be established using the BGP Capabilities specifying
   the speaker is capable of MP-BGP and for the CDNI Address Family.  In
   each of the CDNs at least one MP-BGP speaker will be available
   ensuring connectivity to the CDNI Mesh.

   Internal MP-BGP sessions can be used inside a CDN for propagating
   footprint and connectivity advertisements.  Same mechanisms such as
   route reflectors and/or confederations can be used internally to a
   CDN.



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   A CDN that is operated by an ISP may use the same ASN than the one
   currently used by the ISP.

6.2.  CDNI MP-BGP NLRI

   Two types of CDNI NLRIs are defined: footprint and connectivity.

6.2.1.  CDNI Footprint NLRI and Attributes

   This CDNI NLRI Type (TBD) describes footprint information which
   consists of an IPv4 or IPv6 address prefix.  CDNI Footprint
   Advertisement includes following information (note well that in this
   section we do not aim to describe in details the format of the NLRI
   bur rather focus on the kind of information it should contain):
         RD:ipv4 or RD:ipv6 addresses
         BGP attributes such as: AS_PATH, NEXT_HOP, MED,
                                 Community, ExtCommunity.
         Origin_AS_PATH
         Footprint Identifiers

      where:

   RD is the Route Distinguisher of the route.  When used, it allows to
   distinguish among multiple advertisements of the same prefix (for the
   multihomed case).  The RD is present in CDNI NLRI using CDNI-AF with
   SAFI value set to 128.

   Origin_AS_PATH contains the AS_PATH value that is present in the CDNI
   Footprint Database for this prefix.

   Footprint Identifier describes to which footprint this prefix belongs
   to.  The footprint Identifier represents the ASN of origin of the
   prefix.

   Footprint NLRIs are propagated in the CDNI Mesh according to standard
   MP-BGP rules and MP-BGP attributes such as AS_PATH, NEXT_HOP, MED,
   Local Preference, etc, are updated and used according to the standard
   MP-BGP mechanisms.  For example, AS_PATH is updated and checked so to
   avoid messaging loops.

6.2.2.  CDNI Connectivity NLRI and Attributes

   The CDNI Connectivity NLRI Type (TBD) describes how the CDN connects
   to a given footprint.  Each CDN originates one or more prefixes whose
   purpose is to convey attributes describing how the CDN can reach the
   footprint.  The Connectivity advertisment includes following
   information:




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         RD:ipv4 or RD:ipv6 addresses
         BGP attributes such as: AS_PATH, NEXT_HOP, MED,
                                 Community, ExtCommunity.
         Origin_AS_PATH
         Connected Footprints

         where:

   RD is the Route Distinguisher of the route.  When used, it allows to
   distinguish among multiple advertisements of the same prefix (for the
   multihomed case).  The RD is present in CDNI NLRI using CDNI-AF with
   SAFI value set to 128.  It has to be noted that the CDNI
   Advertisements makes no use of the route distinguisher and therefore
   it has to be set to all zero.

   BGP attributes convey information related to the connectivity of the
   CDN to the footprint.

   Origin_AS_PATH contains the AS_PATH that describes how the CDN is
   connected to the footprint (i.e.: what is the AS hop count).

   Connected Footprints describe which footprints the CDN has
   connectivity to.


7.  Example of CDNI Mesh

   In this section an example of a CDNI Mesh is described as well as the
   CDNI Information that will be originated.
      +-------------------------------------------+
      |           CDNI (partial or full) Mesh     |
      +-------------------------------------------+
          |           |         |           |
      +-------+   +-------+   +-------+   +-------+
      | CDN 1 |   | CDN 2 |   | CDN 3 |   | CDN 4 |
      |       |   | AS600 |   | AS700 |   |  /    |
      |       |   +-------+   +-------+   |/      |
      |       |       |   ____/    |     /|       |
      |       |       |  /         |   /  |       |
      |       |   +-------+   +-------+   |       |
      | AS100 |---| AS200 |---| AS300 |---| AS400 |
      +-------+   +-------+   +-------+   +-------+
         |           |           |           |
   192.168.10/24     |    192.168.30/24      |
                     |                       |
               192.168.20/24           192.168.40/24

                        Figure 2: CDNI Mesh Example



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   We assume different Autonomous Systems (representing different ISPs)
   with their own prefix space.  We also assume four CDNs that are, for
   some of them, on their own AS while others share the AS of their ISP
   (which describe the case where the CDN is managed by the ISP).  The
   Internet is represented by the interconnectivity of the Autonomous
   System.

7.1.  CDNI Footprint Information and Advertisements

   Footprint information will be inferred by each CDN from the BGP-4
   database.  For example, the CDNI Footprint Database in CDN4, located
   in Autonomous System 400, is as follows:
                 IPv4 prefix:                 192.168.10/24
                 AS_PATH:                     300 200 100
                 CDNI Footprint Identifier:   100:000

                 IPv4 prefix:                 192.168.20/24
                 AS_PATH:                     300 200
                 CDNI Footprint Identifier:   200:000

                 IPv4 prefix:                 192.168.30/24
                 AS_PATH:                     300
                 CDNI Footprint Identifier:   300:000

                 IPv4 prefix:                 192.168.40/24
                 AS_PATH:
                 CDNI Footprint Identifier:   400:000

      where:

   IPv4 Prefix is the footprint prefix information.

   AS_PATH is the existing BGP AS_PATH attribute (from the BGP-4
   database) containing the set of ASNs the update has traversed in the
   Internet.

   CDNI Footprint Identifier represents the footprint as a whole.  All
   prefixes part of the same footprint will share the same Footprint
   Identifier.  For CDNI purposes, CDN4 may want to advertise more
   information about the inferred footprint so to tell the CDNI Mesh
   more information about location of the footprint.  For example, part
   of the address space 192.168.40/24 is located in NYC, part is located
   in Chicago and part in LA.  CDN4 may originate new CDNI Footprint
   Information such as:







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                IPv4 prefix:                 192.168.40.64/26
                AS_PATH:
                CDNI Footprint Identifier:   400:001

                IPv4 prefix:                 192.168.40.128/26
                AS_PATH:
                CDNI Footprint Identifier:   400:002

                IPv4 prefix:                 192.168.40.192/26
                AS_PATH:
                CDNI Footprint Identifier:   400:003

   When CDN4 sends out the above advertisements, it will have to update
   both the AS_PATH attribute (in order to prevent BGP message loops as
   well as the Origin-AS_PATH attribute so to preserve the original
   AS_PATH.  Therefore the advertisements CDN4 will send out will be as
   follows:
                IPv4 prefix:                 192.168.40.64/26
                AS_PATH:                     400
                CDNI Footprint Identifier:   400:001
                Origin_AS_PATH               400

                IPv4 prefix:                 192.168.40.128/26
                AS_PATH:                     400
                CDNI Footprint Identifier:   400:002
                Origin_AS_PATH               400

                IPv4 prefix:                 192.168.40.192/26
                AS_PATH:                     400
                CDNI Footprint Identifier:   400:002
                Origin_AS_PATH               400

   When the advertisement is received by the CDNI Mesh neighbors it will
   also be propagated.  For example, CDN3 may receive these
   advertisements and send them to CDN2.  At CDN2 the advertisements
   will contain following information:















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                IPv4 prefix:                 192.168.40.64/26
                AS_PATH:                     300 400
                CDNI Footprint Identifier:   400:001
                Origin_AS_PATH               400

                IPv4 prefix:                 192.168.40.128/26
                AS_PATH:                     300, 400
                CDNI Footprint Identifier:   400:002
                Origin_AS_PATH               400

                IPv4 prefix:                 192.168.40.192/26
                AS_PATH:                     300 400
                CDNI Footprint Identifier:   400:002
                Origin_AS_PATH               400

   where the AS_PATH attributes reflect the path taken by the
   advertisement in the CDNI-Mesh while the Origin_AS_PATH reflects the
   AS_PATH the prefix had at its point of origin (ASN 400).

7.2.  Connectivity Information and Advertisements

   Connectivity advertisements have the dual purpose of describing the
   CDN connectivity to the footprint and the connectivity to other CDNs.
   For example, CDN4 connectivity advertisement will describe the
   footprint connectivity to Footprint Identifiers 400:001, 400:002 and
   400:003.  The following is the advertisement CDN4 will send to its
   MP-BGP neighbors:
                 IPv4 prefix:          192.168.4.4/32
                 AS_PATH:              400
                 Connected footprints: 400:001, 400:002, 400:003

   where:

   IPv4 Prefix is the IPv4 address identifying the CDN (or part of it)
   in the CDNI Mesh.

   AS_PATH contains the AS numbers this update traversed (including the
   AS where this connectivity advertisement has been originated).

   Connected Footprints contains the set of footprint identifiers this
   CDN is directly connected to.

   *** Editor's Note: a mechanism in order to express preference or
   costs to footprints is needed: either through a ranking sequence or
   through explicit preference cost or weight.

   Alternatively, CDN4 may want to advertise 3 distinct Connectivity
   Advertisements for each of the footprints its connected to:



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                 IPv4 prefix:          192.168.4.1/32
                 AS_PATH:              400
                 Connected footprints: 400:001

                 IPv4 prefix:          192.168.4.2/32
                 AS_PATH:              400
                 Connected footprints: 400:002

                 IPv4 prefix:          192.168.4.3/32
                 AS_PATH:              400
                 Connected footprints: 400:003

   Each prefix will carry a different Footprint Identifier so that CDN4
   can separate these advertisements.

   Each CDN may also advertise a set of communities representing the
   capabilities of the CDN.  It is possible for a transit CDN to
   manipulate the set of communities during its propagation.  Example: a
   CDN, prior to propagate the connectivity advertisement of another
   CDN, may strip one or more capabilities from the original
   advertisement.  This will allow to enforce a given path selection by
   upstream CDNs.


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.







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11.  Acknowledgements

   The authors would like to recognize Bruce Davie for his
   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.

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

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-00 (work in
              progress), July 2011.

   [I-D.ietf-cdni-requirements]
              Leung, K. and Y. Lee, "Content Distribution Network
              Interconnection (CDNI) Requirements",
              draft-ietf-cdni-requirements-01 (work in progress),
              October 2011.

   [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.










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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


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

   Email: allan.guillou@sfr.com


   Jan Medved
   Juniper Networks, Inc.
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089
   US

   Email: jmedved@juniper.net















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