Internet Engineering Task Force                         G. Bertrand, Ed.
Internet-Draft                                                E. Stephan
Intended status: Informational                   France Telecom - Orange
Expires: September 27, 2012                                    G. Watson
                                                            T. Burbridge
                                                              P. Eardley
                                                                      BT
                                                                   K. Ma
                                                           Azuki Systems
                                                          March 26, 2012


         Use Cases for Content Delivery Network Interconnection
                      draft-ietf-cdni-use-cases-04

Abstract

   Content Delivery Networks (CDNs) are commonly used for improving the
   End User experience of a content delivery service, at a reasonable
   cost.  This document focuses on use cases that correspond to
   identified industry needs and that are expected to be realized once
   open interfaces and protocols supporting interconnection of CDNs are
   specified and implemented.  The document can be used to guide the
   definition of the requirements to be supported by CDNI interfaces.

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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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 27, 2012.

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



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   Provisions Relating to IETF Documents
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   it for publication as an RFC or to translate it into languages other
   than English.































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Abbreviations  . . . . . . . . . . . . . . . . . . . . . .  4
     1.3.  Rationale for Multi-CDN Systems  . . . . . . . . . . . . .  5
   2.  Footprint Extension Use Cases  . . . . . . . . . . . . . . . .  7
     2.1.  Geographic Extension . . . . . . . . . . . . . . . . . . .  7
     2.2.  Inter-Affiliates Interconnection . . . . . . . . . . . . .  7
     2.3.  ISP Handling of Third-Party Content  . . . . . . . . . . .  8
     2.4.  Nomadic Users  . . . . . . . . . . . . . . . . . . . . . .  8
   3.  Offload Use Cases  . . . . . . . . . . . . . . . . . . . . . .  9
     3.1.  Overload Handling and Dimensioning . . . . . . . . . . . .  9
     3.2.  Resiliency . . . . . . . . . . . . . . . . . . . . . . . . 10
       3.2.1.  Failure of Content Delivery Resources  . . . . . . . . 10
       3.2.2.  Content Acquisition Resiliency . . . . . . . . . . . . 10
   4.  CDN Capability Use Cases . . . . . . . . . . . . . . . . . . . 11
     4.1.  Device and Network Technology Extension  . . . . . . . . . 11
     4.2.  Technology and Vendor Interoperability . . . . . . . . . . 12
     4.3.  QoE and QoS Improvement  . . . . . . . . . . . . . . . . . 12
   5.  Enforcement of Content Delivery Policy . . . . . . . . . . . . 12
   6.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 13
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 14
   Appendix A.  Content Service Providers' Delivery Policies  . . . . 15
     A.1.  Content Delivery Policy Enforcement  . . . . . . . . . . . 15
     A.2.  Secure Access  . . . . . . . . . . . . . . . . . . . . . . 16
     A.3.  Branding . . . . . . . . . . . . . . . . . . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16



















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1.  Introduction

   Content Delivery Networks (CDNs) are commonly used for improving the
   End User experience of a content delivery service, at a reasonable
   cost.  This document focuses on use cases that correspond to
   identified industry needs and that are expected to be realized once
   open interfaces and protocols supporting interconnection of CDNs are
   specified and implemented.  The document can be used to guide the
   definition of the requirements to be supported by the various CDNI
   interfaces defined in [I-D.ietf-cdni-problem-statement].

   This document identifies the main motivations for a CDN Provider to
   interconnect its CDN:

   o  CDN Footprint Extension Use Cases (Section 2)

   o  CDN Offload Use Cases (Section 3)

   o  CDN Capability Use Cases (Section 4)

   Then, the document highlights the need for interoperability to
   exchange and enforce content delivery policies (Section 5).

1.1.  Terminology

   We adopt the terminology described in
   [I-D.ietf-cdni-problem-statement], [I-D.davie-cdni-framework],
   [RFC3466], and [RFC3568].

   We extend this terminology with the following terms.

   Access CDN:

   A CDN that is directly connected to the End User's access.  An Access
   CDN may have specific information about the End User and the network,
   for instance, End User's profile and access capabilities.

   Delivering CDN:

   The CDN that delivers the requested piece of content to the End User.
   In particular, the Delivering CDN can be an Access CDN.

1.2.  Abbreviations

   o  CDN: Content Delivery Network also known as Content Distribution
      Network





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   o  CSP: Content Service Provider

   o  dCDN: downstream CDN

   o  DNS: Domain Name System

   o  DRM: Digital Rights Management

   o  EU: End User

   o  ISP: Internet Service Provider

   o  NSP: Network Service Provider

   o  QoE: Quality of Experience

   o  QoS: Quality of Service

   o  uCDN: upstream CDN

   o  URL: Uniform Resource Locator

   o  WiFi: Wireless Fidelity

1.3.  Rationale for Multi-CDN Systems

   Content Delivery Networks (CDNs) are used to deliver content because
   they can:

   o  improve the experience for the End User; for instance delivery has
      lower latency (decreased round-trip-time between the user and the
      delivery server) and better robustness,

   o  reduce the network operator's costs; for instance, lower delivery
      cost (reduced bandwidth usage) for cacheable content,

   o  reduce the Content Service Provider's (CSP) costs, such as
      datacenter capacity, space, and electricity consumption, as
      popular content is delivered through the CDN rather than through
      the CSP's servers.

   Indeed, many Network Service Providers (NSPs) and enterprise service
   providers are deploying or have deployed their own CDNs.  Despite the
   potential benefits of interconnecting CDNs, today each CDN is a
   standalone network.  The objective of CDN Interconnection is to
   overcome this restriction: the interconnected CDNs should be able to
   collectively behave as a single delivery infrastructure.




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   An example is depicted in Figure 1.  Two CDN Providers establish a
   CDN Interconnection.  The Content Service Provider CSP-1 reaches an
   agreement with CDN Provider 'A' for the delivery of its content.  CDN
   Provider 'A' and CDN Provider 'B' agree to interconnect their CDNs.

   When a User Agent requests content from CSP-1, CDN-A considers that
   delivery by CDN-B is appropriate, for instance, because CDN-B is an
   Access CDN and the user is directly attached to it.  CDN-A has
   delegated the handling of requests for CSP-1's content through the
   CDN Interconnection agreement, thus, the content is actually
   delivered from CDN-B.

   The End User benefits from this arrangement through a better Quality
   of Experience (QoE), because the content is delivered from a nearby
   Surrogate.  CDN Provider 'A' benefits because it does not need to
   deploy such an extensive CDN, whilst CDN Provider 'B' may receive
   some compensation for the delivery.  CSP-1 benefits because it only
   needs to make one business agreement and one physical connection,
   with CDN Provider 'A', but its End Users get a service quality as
   though CSP-1 had also gone to the trouble of making a business
   agreement with CDN Provider 'B'.


    +-------+ +-------+
    | CSP-1 | | CSP-2 |
    +-------+ +-------+
        |         |
       ,--,--,--./            ,--,--,--.
    ,-'          `-.       ,-'          `-.
   (CDN Provider 'A')=====(CDN Provider 'B')
    `-.  (CDN-A) ,-'       `-. (CDN-B)  ,-'
       `--'--'--'             `--'--'--'
                                  |
                            +------------+
                            | User Agent |
                            +------------+
    === CDN Interconnection


                                 Figure 1

   To extend the example, another Content Service Provider, CSP-2, may
   also reach an agreement with CDN Provider 'A'.  But it does not want
   its content to be distributed by CDN Provider B; for example, CSP-2
   may not have distribution rights in the country where CDN Provider
   'B' operates.  This example illustrates that policy considerations
   are an important part of CDNI.




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2.  Footprint Extension Use Cases

   Footprint extension is expected to be a major use case for CDN
   Interconnection.

2.1.  Geographic Extension

   In this use case, the CDN Provider wants to extend the geographic
   distribution that it can offer to its CSPs:

   o  without compromising the quality of delivery,

   o  without incurring additional transit and other network costs that
      would result from serving content from geographically or
      topologically remote Surrogates.

   If there are several CDN Providers that have a geographically limited
   footprint (e.g., restricted to one country), or do not serve all End
   Users in a geographic area, then interconnecting their CDNs enables
   these CDN Providers to provide their services beyond their own
   footprint.

   As an example, suppose a French CSP wants to distribute its TV
   programs to End Users located in France and various countries in
   North Africa.  It asks a French CDN Provider to deliver the content.
   The French CDN Provider's network only covers France, so it makes an
   agreement with another CDN Provider that covers North Africa.
   Overall, from the CSP's perspective the French CDN Provider provides
   a CDN service for both France and North Africa.

   In addition to video, this use case applies to other types of content
   such as automatic software updates (browser updates, operating system
   patches, virus database update, etc).

2.2.  Inter-Affiliates Interconnection

   In the previous section, we have described the case of geographic
   extension between CDNs operated by different entities.  A large CDN
   Provider may also operate CDNs from several subsidiaries (which may
   rely on different CDN technologies, see Section 4.2).  In certain
   circumstances, the CDN Provider needs to make its CDNs interoperate
   to provide a consistent service to its customers on its whole
   footprint.  For example, the CDN Provider might want to expose a
   single set of interfaces to the CSPs.







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2.3.  ISP Handling of Third-Party Content

   Consider an ISP carrying to its subscribers a lot of content that
   comes from a third party CSP and that is injected into the access
   network by an Authoritative CDN Provider.  There are mutual benefits
   to the Access CDN, the Authoritative CDN, and the CSP that would make
   a case for establishing a CDNI agreement.  For example:

   o  Allow the CSP to offer improved QoE and QoE services to
      subscribers, for example, QoS and reduced round trip time.

   o  Allow the Authoritative CDN to reduce hardware capacity and
      footprint, by using the ISP caching and delivery capacity.

   o  Allow the ISP to reduce traffic load on some segments of the
      network by caching inside of the ISP network.

   o  Allow the ISP to influence and/or control the traffic ingestion
      points.

   o  Allow the ISP to derive some incremental revenue for transport of
      the traffic and to monetize QoE services.

2.4.  Nomadic Users

   In this scenario, a CSP wishes to allow End Users who move between
   CDNs to continue to access their content.  The motivation of this
   case is to allow nomadic End Users to maintain access to content with
   a consistent QoE, across a range of devices and/or geographic
   regions.

   This use case covers situations like:

   o  End Users moving between different CDN Providers, which may reside
      within the same geographic region or different geographic regions,

   o  End Users switching between different devices or delivery
      technologies, as discussed in Section 4.

   The term "Nomadic" does not necessarily relate to geographic roaming.

   Consider the following example, illustrated in Figure 2: End User A
   has subscription to a broadband service from NSP A, her "home NSP".
   NSP A hosts CDN-A.  Ordinarily, when End User A accesses content via
   NSP A (her "home NSP") the content is delivered from CDN-A, which in
   this example is within NSP A's network.

   However, while End User A is not connected to NSP A's network, for



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   example, because it is connected to a WiFi provider or mobile
   network, End User A can also access the same content.  In this case,
   End User A may benefit from accessing the same content but delivered
   by an alternate CDN (CDN-B), in this case, hosted in the network of
   the WiFi or mobile provider, rather than from CDN-A in NSP A's
   network.


       +-------+
       |Content|
       +-------+
           |
       ,--,--,--.             ,--,--,--.
    ,-'  NSP A   `-.       ,-'  NSP B   `-.
   (    (CDN-A)     )=====(    (CDN-B)     )
    `-.          ,-'       `-.          ,-'
       `--'--'--'             `--'--'--'
            |                     |
      +------------+      +---------------+
      + EU A (home)|      | EU A (nomadic)|
      +------------+      +---------------+
    === CDN Interconnection


                                 Figure 2

   The alternate CDN (CDN-B) is allowed to distribute the content of CSP
   A to End User A; however, no other End Users in the region of CDN-B
   are allowed to retrieve the content unless they too have such an
   agreement for nomadic access to content.

   Depending on CSP's content delivery policies (see Appendix A.1), a
   user moving to a different geographic region may be subject to geo-
   blocking content delivery restrictions.  In this case, he/she may not
   be allowed to access some pieces of content.


3.  Offload Use Cases

3.1.  Overload Handling and Dimensioning

   A CDN is likely to be dimensioned to support an expected maximum
   traffic load.  However, unexpected spikes in content popularity
   (flash crowd) may drive load beyond the expected peak.  The prime
   recurrent time peaks of content distribution may differ between two
   CDNs.  Taking advantage of the different traffic peak times, a CDN
   may interconnect with another CDN to increase its effective capacity
   during the peak of traffic.  This brings dimensioning savings to the



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   CDNs as they can use the resources of each other during their
   respective peaks of activity.

   Offload also applies to planned situations where a CDN Provider needs
   CDN capacities in a particular region during a short period of time.
   For example, a CDN can offload traffic to another CDN during a
   specific maintenance operation or for covering the distribution of a
   special event.  For instance, consider a TV-channel which has
   exclusive distribution rights on a major event, such as a
   celebrities' wedding, or a major sport competition.  The CDNs that
   the TV-channel uses for delivering the content related to this event
   are likely to experience a flash crowd during the event and to need
   offloading traffic, while other CDNs will support a more usual
   traffic load and be able to handle the offloaded traffic.

   In this use case, the Delivering CDN on which requests are offloaded
   should be able to handle the offloaded requests.  Therefore, the uCDN
   might require information on the dCDNs to be aware of the amount of
   traffic it can offload to every dCDN.

3.2.  Resiliency

3.2.1.  Failure of Content Delivery Resources

   It is important for CDNs to be able to guarantee service continuity
   during partial failures (e.g., failure of some Surrogates).  In
   partial failure scenarios, a CDN Provider has at least two options:
   (1) depending on traffic management policies, forward some requests
   to the CSP's origin servers, and (2) redirect some requests toward
   another CDN, which must be able to serve the redirected requests.
   The second option is a use case for CDNI.

3.2.2.  Content Acquisition Resiliency

   Source content acquisition may be handled in one of two ways:

   o  CSP origin, where a CDN acquires content directly from the CSP's
      origin server, or

   o  CDN origin, where a downstream CDN acquires content from a
      Surrogate within an upstream CDN.

   The ability to support content acquisition resiliency, is an
   important use case for interconnected CDNs.  When the content
   acquisition source fails, the CDN might switch to another content
   acquisition source.  Similarly, when several content acquisition
   sources are available, a CDN might balance the load between these
   multiple sources.



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   Though other server and/or DNS load balancing techniques may be
   employed in the network, interconnected CDNs may have a better
   understanding of origin server availability and be better equipped to
   both distribute load between origin servers and attempt content
   acquisition from alternate origin servers when acquisition failures
   occur.  When normal content acquisition fails, a CDN may need to try
   other origin server options, e.g.:

   o  an upstream CDN may acquire content from an alternate CSP origin
      server,

   o  a downstream CDN may acquire content from an alternate Surrogate
      within an upstream CDN,

   o  a downstream CDN may acquire content from an alternate upstream
      CDN, or

   o  a downstream CDN may acquire content directly from the CSP's
      origin server.

   Though content acquisition protocols are beyond the scope of CDNI,
   the selection of content acquisition sources should be considered.


4.  CDN Capability Use Cases

4.1.  Device and Network Technology Extension

   In this use case, the CDN Provider may have the right geographic
   footprint, but may wish to extend the supported range of devices and
   User Agents or the supported range of delivery technologies.  In this
   case, a CDN Provider may interconnect with a CDN that offers
   services:

   o  that the CDN Provider is not willing to provide or,

   o  that its own CDN is not able to support.

   The following examples illustrate this use case:

   1.  CDN-A cannot support a specific delivery protocol.  For instance,
       CDN-A may interconnect with CDN-B to serve a proportion of its
       traffic that requires HTTPS.  CDN-A may use CDN-B's footprint
       (which may overlap with its own) to deliver HTTPS without needing
       to deploy its own infrastructure.  This case could also be true
       of other formats, delivery protocols (RTMP, RTSP, etc.) and
       features (specific forms of authorization such as tokens, per
       session encryption, etc.).



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   2.  CDN-A has footprint covering traditional fixed line broadband and
       wants to extend coverage to mobile devices.  In this case, CDN-A
       may contract and interconnect with CDN-B who has both:

       *  physical footprint inside the mobile network,

       *  the ability to deliver content over a protocol that is
          required by specific mobile devices.

   These cases can apply to many CDN features that a given CDN Provider
   may not be able to support or not be willing to invest in, and thus,
   that the CDN Provider would delegate to another CDN.

4.2.  Technology and Vendor Interoperability

   A CDN Provider may deploy a new CDN to run alongside its existing
   CDN, as a simple way of migrating its CDN service to a new
   technology.  In addition, a CDN Provider may have a multi-vendor
   strategy for its CDN deployment.  Finally, a CDN Provider may want to
   deploy a separate CDN for a particular CSP or a specific network.  In
   all these circumstances, CDNI benefits the CDN Provider, as it
   simplifies or automates some inter-CDN operations (e.g., migrating
   the request routing function progressively).

4.3.  QoE and QoS Improvement

   Some CSPs are willing to pay a premium for enhanced delivery of
   content to their End Users.  In some cases, even if the CDN Provider
   could deliver the content to the End Users, it cannot meet the CSP's
   service level requirements.  As a result, the CDN Provider may
   establish a CDN Interconnection agreement with another CDN Provider
   that can provide the expected QoE to the End User, e.g., via an
   Access CDN able to deliver content from Surrogates located closer to
   the End User and with the required service level.


5.  Enforcement of Content Delivery Policy

   An important aspect of the above use cases is that CSPs commonly want
   to enforce content delivery policies.  A CSP may want to define
   content delivery policies that specify when, how, and/or to whom the
   CDN delivers content.  These policies apply to all interconnected
   CDNs (uCDNs and dCDNs) in the same or similar way that a CSP can
   define content delivery policies for content delivered by a single,
   non-interconnected CDN.  Appendix A provides examples of CSP defined
   policies.





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6.  Acknowledgments

   The authors would like to thank Kent Leung, Francois Le Faucheur, Ben
   Niven-Jenkins, and Scott Wainner for lively discussions, as well as
   for their reviews and comments on the mailing list.

   They also thank the contributors of the EU FP7 OCEAN and ETICS
   projects for valuable inputs.


7.  IANA Considerations

   This memo includes no request to IANA.


8.  Security Considerations

   CDN Interconnection, as described in this document, has a wide
   variety of security issues that should be considered.

   In addition to the security considerations within the uCDN and dCDN,
   four contexts involve security and trust issues:

   a.  The relationship between the CSP and the uCDN: the main contract
       arrangement for distribution, which authorizes the uCDN to
       acquire content on CSP's origin servers and to deliver it,
       potentially with content delivery restrictions.

   b.  The relationship between the uCDN and dCDN: the transitive trust
       relationship that extends the contract defined in (a) above and
       that authorizes the dCDN to acquire content on uCDN's or CSP's
       origin servers and to deliver it, potentially with content
       delivery restrictions.

   c.  The relationship between the End User and dCDN: the recognition
       of right to download predicated on (b) above.

   d.  The relationship between the End User and the CSP: the contract
       that authorizes the End User to access the content.

   CDNI should enable the four parties (CSP, uCDN, dCDN, End User) to
   negotiate a security method or a method for confirming authorization
   along the chain of trust (CSP -> uCDN -> dCDN -> End User).

   The security issues fall into three general categories:

   o  CSP Trust: where the CSP may have negotiated service level
      agreements for delivery quality of service with the uCDN, and/or



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      configured distribution policies (e.g., geo-restrictions,
      availability windows, or other licensing restrictions), which it
      assumes will be upheld by dCDNs to which the uCDN delegates
      requests.  Furthermore, billing and accounting information must be
      aggregated from dCDNs with which the CSP may have no direct
      business relationship.  These situations where trust is delegated
      must be handled in a secure fashion to ensure CSP confidence in
      the CDN interconnection.

   o  Client Transparency: where the client device or application which
      connects to the CDN must be able to interact with any dCDN using
      its existing security and DRM protocols (e.g., cookies,
      certificate-based authentication, custom DRM protocols, URL
      signing algorithms, etc.) in a transparent fashion.

   o  CDN Infrastructure Protection: where the dCDNs must be able to
      identify and validate delegated requests, in order to prevent
      unauthorized use of the network and to be able to properly bill
      for delivered content.  A dCDN may not wish to advertise that it
      has access to or is carrying content for the uCDN or CSP,
      especially if that information may be used to enhance denial of
      service attacks.  CDNI interfaces and protocols should attempt to
      minimize overhead for dCDNs.

   This document focuses on the motivational use cases for CDN
   Interconnection, and does not analyze these threats in detail.


9.  References

9.1.  Normative References

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

9.2.  Informative References

   [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-problem-statement]
              Niven-Jenkins, B., Faucheur, F., and N. Bitar, "Content
              Distribution Network Interconnection (CDNI) Problem
              Statement", draft-ietf-cdni-problem-statement-04 (work in
              progress), March 2012.




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   [I-D.ietf-cdni-requirements]
              Leung, K. and Y. Lee, "Content Distribution Network
              Interconnection (CDNI) Requirements",
              draft-ietf-cdni-requirements-02 (work in progress),
              December 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.


Appendix A.  Content Service Providers' Delivery Policies

   CSPs commonly apply different delivery policies to given sets of
   content assets delivered through CDNs.  Interconnected CDNs need to
   support these policies.  This annex presents examples of CSPs'
   delivery policies and their consequences on CDNI operations.

A.1.  Content Delivery Policy Enforcement

   The content distribution policies that a CSP attaches to a content
   asset may depend on many criteria.  For instance, distribution
   policies for audiovisual content often combine:

   o  temporal constraints (e.g., available for 24 hours, available 28
      days after DVD release, etc.),

   o  resolution-based constraints (e.g., high definition vs. standard
      definition), and

   o  geolocation-based constraints (e.g., per country).

   dCDN delegation and Surrogate selection decisions are influenced by
   these policies:

   o  dCDN delegation and/or Surrogates selection may fail if the
      availability window for the requested content is not active,

   o  dCDN delegation may fail if the content resolution has been
      specified by the CSP as being too high for distribution via the
      dCDN,

   o  Surrogate selection may fail if the content resolution has been
      specified by the CSP as being too high for distribution via the



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      current CDN,

   o  dCDN delegation may fail if the footprint of the dCDN is outside
      of the delivery footprint for the requested content, or

   o  Surrogate selection may fail if the footprint of the current CDN
      is outside of the delivery footprint for the requested content.

   These policy considerations permit preventing premature access to
   pre-positioned content, preventing content licensing violations, and
   enforcing geo-blocking policies.

A.2.  Secure Access

   Many protocols exist for delivering content to End Users.  CSPs may
   dictate a specific protocol or set of protocols which are acceptable
   for delivery of their content, especially in the case where content
   protection or user authentication is required (e.g., must use HTTPS).
   CSPs may also perform per-request authentication/authorization
   decision and then have the CDNs enforce that decision (e.g., must
   validate URL signing, etc.).

A.3.  Branding

   Preserving the branding of the CSP throughout delivery is often
   important to the CSP.  CSPs may desire to offer content services
   under their own name, even when the associated CDN service involves
   other CDN Providers.  For instance, a CSP may desire to ensure that
   content is delivered with URIs appearing to the End Users under the
   CSP's own domain name, even when the content delivery involves
   separate CDN Providers.  The CSP may wish to prevent the delivery of
   its content by specific dCDNs that lack support for such branding
   preservation features.

   Analogous cases exist when the uCDN wants to offer CDN services under
   its own branding even if dCDNs are involved.  Similarly, a CDN
   Provider might wish to restrict the delivery delegation to a chain
   that preserves its brand visibility.













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Authors' Addresses

   Gilles Bertrand (editor)
   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.com


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

   Email: emile.stephan@orange.com


   Grant Watson
   BT
   pp GDC 1 PP14, Orion Building, Adastral Park, Martlesham
   Ipswich,   IP5 3RE
   UK

   Email: grant.watson@bt.com


   Trevor Burbridge
   BT
   B54 Room 70, Adastral Park, Martlesham
   Ipswich,   IP5 3RE
   UK

   Email: trevor.burbridge@bt.com


   Philip Eardley
   BT
   B54 Room 77, Adastral Park, Martlesham
   Ipswich,   IP5 3RE
   UK

   Email: philip.eardley@bt.com





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   Kevin Ma
   Azuki Systems
   43 Nagog Park
   Acton,   MA 01720
   USA

   Phone: +1 978 844 5100
   Email: kevin.ma@azukisystems.com











































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