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Versions: 00 01 02 draft-ietf-cdni-use-cases

Internet Engineering Task Force                              G. Bertrand
Internet-Draft                                                E. Stephan
Intended status: Informational                   France Telecom - Orange
Expires: July 17, 2011                                  January 13, 2011


       Use Cases for Content Distribution Network Interconnection
                    draft-bertrand-cdni-use-cases-00

Abstract

   This document depicts use cases for content delivery network (CDN)
   interconnection based on Orange experiments.  The use cases are
   divided in the two following categories.  Category 1 use cases
   present situations that require a footprint extension for existing
   CDNs.  Category 2 use cases include additional situations where CDN
   interconnection would be desirable in a longer term.

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
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   This Internet-Draft will expire on July 17, 2011.

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   described in the Simplified BSD License.

   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
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   than English.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  Acronyms . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  High Level Use Cases for Multi-CDN Systems . . . . . . . . . .  5
     2.1.  Footprint Extension Use Cases  . . . . . . . . . . . . . .  5
       2.1.1.  CDN Interconnection inside one CDSP  . . . . . . . . .  5
       2.1.2.  CDN Interconnection between CDSPs  . . . . . . . . . .  5
     2.2.  Additional Potential Use Cases . . . . . . . . . . . . . .  6
       2.2.1.  CDN Interconnection for CDN Overload Handling  . . . .  6
       2.2.2.  CDN Interconnection for CDN Resiliency . . . . . . . .  6
       2.2.3.  Inter-Silos CDN Interconnection inside one CDSP  . . .  7
   3.  Experiment with Existing CDN Solutions and Lessons Learned . .  8
     3.1.  Description of the Experiments . . . . . . . . . . . . . .  8
     3.2.  Gaps in Existing Solutions and Need for Specifications . .  9
   4.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  9
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10













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1.  Introduction

   This document depicts use cases for content delivery network (CDN)
   interconnection based on Orange experiments.  The use cases are
   divided in the two following categories.  Category 1 use cases
   present situations that require a footprint extension for existing
   CDNs.  Category 2 use cases include additional situations where CDN
   interconnection would be desirable in a longer term.

   The present document complements [I-D.watson-cdni-use-cases].  The
   two drafts will be merged during the next weeks.

1.1.  Terminology

   Except for the terms defined below, we adopt the terminology
   described in [RFC3466], [RFC3568], and [RFC3570].

   Problem statement draft [I-D.jenkins-cdni-problem-statement] defines
   a set of terms.  Below we recall only the terms used in the memo.

   Content Service Provider (CSP):

   Provides Content Services to Users.  A CSP may own the content made
   available as part of the Content Service, or may license content
   rights from another party.

   Content Service:

   The service offered by a CSP.  The Content Service encompasses the
   complete service which may be wider than just the delivery of items
   of Content, e.g. the Content Service also includes any middle-ware,
   key distribution, program guide, etc. which may not require any
   direct interaction with the CDN.

   Content Distribution Network (CDN) / Content Delivery Network (CDN):

   A type of network in which the components are arranged for more
   effective delivery of content to User Agents.

   Content Delivery Service

   Set of services offered to CSPs for delivering their contents through
   a single Content Delivery Network or a federation of Content Delivery
   Networks.

   CDN Service Provider (CDSP):

   An administrative entity who operates a CDN over a NSP or over the



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   Internet.

   CDN federation

   Set of CDNs that maintain a CDNI relationship to one another.  The
   federation of CDNs can interconnect CDNs operated by the same CDSP or
   operated by distinct CDSPs.

   Authoritative CDN (aCDN):

   The CDSP contracted by the CSP for delivery of contents by this CDN
   or by its downstream dCDNs.

   Downstream CDN (dCDN):

   A CDSP which is contacted by an aCDN to achieve the delivery of
   content to users.

   Access CDN

   A CDN that is the connected to the end-user's access and has
   information about the end-user's access capabilities and profile.

   Delivering CDN

   The CDN that delivers the requested content asset to the end-user.
   In particular, the delivering CDN can be an access CDN.

   CDN Interconnection(CDNI):

   Relationship between two CDNs that enables a CDN to provide content
   delivery services on behalf of another CDN.  It relies on a set of
   interfaces over which two CDNs communicate in order to achieve the
   delivery of content to users by one CDN (the downstream CDN) on
   behalf of another CDN (the upstream CDN).

1.2.  Acronyms

   [Ed.  Note: List of acronyms to be updated later ]

   o  ISP

   o  NSP

   o  STB

   o  PC




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   o  QoS QoE VoD WiFi 3G


2.  High Level Use Cases for Multi-CDN Systems

   The prevalent use cases for CDNI are presented according to the CDSPs
   main reason for interconnecting their CDNs.  They are classified
   according to their level of priority for the CDSPs.

   The CDNI model helps at building a federation of Content Delivery
   Networks that collaborate, allowing Content Delivery Service
   Providers to offer Content Service Providers a set of consistent
   delivery services throughout the CDN Federation.  Let's take an
   example.  CDSP A and B respectively operate CDNa and CDNb.  They
   establish a CDNI relationship for building a CDN federation CDNa-b
   that consists of CDNa and CDNb.  CDSP A reaches an agreement with
   content service provider CSPa.  CDSPa services rely on the CDN
   federation CDNa-b.  Meanwhile, CDSP B reaches an agreement with
   content service provider CSPb.  These services also rely on the CDN
   federation CDNa-b.

2.1.  Footprint Extension Use Cases

2.1.1.  CDN Interconnection inside one CDSP

   A Large Content delivery service provider (CDSP) operates the CDNs of
   a set of subsidiaries from different countries, and these CDNs can
   rely on different CDN solutions.  To provide a consistent service to
   his customers on its whole footprint, in certain circumstances, the
   CDSP needs to make its CDNs interoperate.

   Note that currently, the distribution of some content is restricted.
   For instance, distribution rights for audiovisual content are often
   negotiated per country.


   [Ed. Note: FIGURE TO BE INCLUDED]



   Figure 1: [Ed.  Note: Legend to be added ]

2.1.2.  CDN Interconnection between CDSPs

   Several CDSPs have a geographically limited footprint (e.g., a
   country), or do not serve all end-users in a geographic area.
   Interconnecting CDNs enables CDSPs to provide their services beyond
   their own footprint by relying on other CDNs.



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   End-users in various countries access TV shows episodes.  The CSP
   that distributes the TV show asks a French CDSP to deliver the serie
   to several countries.  The French CDSP make an agreement with an
   external CDSP that covers North Africa to provide a CDN service for
   France and North Africa.

   This use case applies to other types of contents like automatic
   software updates (browser updates, operating system patches, or virus
   database update...).

2.2.  Additional Potential Use Cases

2.2.1.  CDN Interconnection for CDN Overload Handling

   The support of prime time traffic load requires overdimensioning the
   CDNs.  However, prime time of content distribution may differ between
   two CDNs.  Therefore, two CDNs may benefit from dimensioning savings
   by using resources of the other CDN during the prime time.

   During a traffic peak, a CDSP redirects some traffic load toward
   another CDSP (for instance, geographically close).

2.2.2.  CDN Interconnection for CDN Resiliency

   It is important for CDNs to be able to guarantee service continuity
   during partial failures (e.g., failure of a set of surrogates).  In
   partial failure scenarios, a CDSP could redirect some requests toward
   another CDN.  This downstream CDN must be able to serve the
   redirected requests or, depending on traffic management policies, to
   forward these requests to the CSP origin server.





















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                 --------------                    --------------
                /   CDN1       \                  /   CDN2       \
                |  ,---.       |                  |  ,---.       |
    +---+       | .     )      |                  | .     )      |
    |CSP|*******| |`---'|      |__________________| |`---'|      |
    +---+       | |     |      |    Acquisition   | |     |      |
                | (     )      |                  | (     )      |
                |  `---'       |                  |  `---'       |
                |+-----------+ |                  |,------------.|
                ||Req-Routing| |                  .|Delivery    ||
                \+-----------+ /                  \`------------'/
                  ------------                     .-'-----------
                        |                       .-'
                        | --------------- >  .-'
                        |    Redirect     .-'
                        |              .-'
                        |           .-'
                        |        .-'
                        |     .-'
                        |  .-'
                     +-----+
                     | User|
                     +-----+


   Figure 3: Example of CDN Interconnection for failure resiliency

2.2.3.  Inter-Silos CDN Interconnection inside one CDSP

   ISPs deployed platforms per service or per network technology.  They
   are deploying CDNs or enhancing existing platforms to CDN.  It is
   desirable in certain circumstances to share the content or the
   resources among these CDNs.

   It is desirable to have the ability to provide content to different
   terminals and through different access technologies, possibly served
   by different CDNs.  As depicted in Figure 2, an end-user can use his
   tablet to download a VoD through WiFi (1) from CDN1 and then switch
   to 3G network (2), which is served by CDN2.  The end user should be
   able to access the selected VoD content through any access network
   technology.  Consequently, every considered CDN must have access to
   this VoD content.  One way to proceed consists in having an ingestion
   interface among the CDNs to access the content.

   Replication of the requested VoD content in the CDN serving the
   terminal (a) enables controlling the QoS of the VoD distribution to
   the terminal used by the end-user.  In another situation, the serving
   of the CoD without replication (b) will save storage resources.



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   The end-user's experience improves thanks to an increase of the
   number of situations where the end-user can access the service.



              --------------                    --------------
             /   CDN1       \                  /   CDN2       \
             |  Fixed       |                  |  Mobile      |
             |  ,---.       |                  |  ,---.       |
    +---+    | .     )      |        (a)       | .     )      |
    |CSP|****| |`---'|      |''''`---------.....>|`---'|      |
    +---+    | |     |      -..  Acquisition   | |     |      |
             | (     )      |  `-.._           | (     )      |
             |  `---'       |       `-..       |  `---'       |
             |,------------.|       (b) ``-._  |,------------.|
             ||Delivery    ||                `->.  Delivery  ||
             \`------------'/                  \`------------'/
              ----------+---                    -----*--+-----
                        :                            *  |
                        :                            *  |
                     +........+                     +--------+
                     : Tablet : (1)                 | Tablet |(2)
                     +........+                     +--------+



   Figure 2: Example of Inter-Silos CDN Interconnection


3.  Experiment with Existing CDN Solutions and Lessons Learned

3.1.  Description of the Experiments

   To illustrate the realism of the short term scenario described in
   previous sections, we present here the summary of some of our CDNI
   experiments.  These experiments will be further detailed in a
   separate draft.

   We have interconnected two CDNs (CDN A and CDN B)operated by
   different subsidiaries of a large CDSP.  The CDNs cover two different
   countries henceforth referred to as Country A and Country B. The CDNI
   experiment supported the services of two CSPs (CSP A and CSP B).

   In our first experiment, CSP A has an agreement with CDN A for
   content delivery to end-users located in Country A and Country B. CDN
   A has an agreement with CDN B, so that CDN A can delegate to CDN B
   the delivery of content from CSP A to end-users located in Country B.
   When CDN A receives a content request related to CSP A and from an



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   end-user in Country B, it redirects the end-user to the appropriate
   content on CDN B. If CDN B does not have a local copy of the
   requested content yet (cache miss), CDN B ingests the content from
   CDN A. If CDN A does neither have a local copy of the requested
   content, it requests it from the CSP's origin servers before sending
   it to CDN B.

   In our second experiment, CSP B has an agreement with CDN B for
   content delivery to end-users located in Country A and Country B. CDN
   B has an agreement with CDN A, so that CDN B can delegate to CDN A
   the delivery of content from CSP B to end-users located in Country A.
   When CDN B receives a content request related to CSP B and from an
   end-user in Country A, it redirects the end-user to the appropriate
   content on CDN A. If CDN A does not have a local copy of the
   requested content yet (cache miss), it requests the content directly
   from the CSP's origin servers.

   The differences between the two experiments above are the ingestion
   operations and the roles of CDN A and B, which rely on CDN solutions
   from different vendors.

3.2.  Gaps in Existing Solutions and Need for Specifications

   Our experiments have shown that the current CDN technologies suffer
   from the following limitations.

   o  The content management policies must be defined manually.

   o  The target URLs for the request redirection must also be defined
      manually.

   o  The content ingestion worked only in pull mode...

   To address more sophisticated scenarios, we consider that common
   interfaces are required for request routing among interconnected CDNs
   and for the exchange of content distribution metadata.


4.  Acknowledgments

   The authors would like to thank the contributors of the EU FP7 OCEAN
   project for valuable input and discussions.


5.  IANA Considerations

   This memo includes no request to IANA.




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6.  Security Considerations

   CDN interconnect, as described in this document, has a wide variety
   of security issues that should be considered.  For example, every
   interconnected CDN should be able to assess if it must serve a
   delegated request or if this request is delegated by a non-allowed
   CDN.  The CDNs should also be protected so as to avoid being
   overwhelmed by delegated requests.  This document focuses on the
   technical use cases for CDN interconnect, and therefore, does not
   analyze the threats in details.


7.  References

7.1.  Normative References

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

7.2.  Informative References

   [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-00 (work
              in progress), December 2010.

   [I-D.watson-cdni-use-cases]
              Watson, G., "CDN Interconnect Use Cases",
              draft-watson-cdni-use-cases-00 (work in progress),
              January 2011.

   [RFC3466]  Day, M., Cain, B., Tomlinson, G., and P. Rzewski, "A Model
              for Content Internetworking (CDI)", RFC 3466,
              February 2003.

   [RFC3568]  Barbir, A., Cain, B., Nair, R., and O. Spatscheck, "Known
              Content Network (CN) Request-Routing Mechanisms",
              RFC 3568, July 2003.

   [RFC3570]  Rzewski, P., Day, M., and D. Gilletti, "Content
              Internetworking (CDI) Scenarios", RFC 3570, July 2003.









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Authors' Addresses

   Gilles Bertrand
   France Telecom - Orange
   38-40 rue du General Leclerc
   Issy les moulineaux,   92130
   FR

   Phone: +33 1 45 29 89 46
   Email: gilles.bertrand@orange-ftgroup.com


   Stephan Emile
   France Telecom - Orange
   2 avenue Pierre Marzin
   Lannion  F-22307
   France

   Email: emile.stephan@orange-ftgroup.com
































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