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Network Working Group                                              K. Ma
Internet-Draft                                                   R. Nair
Intended status: Informational                       Azuki Systems, Inc.
Expires: September 8, 2011                                 March 7, 2011



    Content Distribution Network Interconnection (CDNI) Publisher Use
                 Cases draft-ma-cdni-publisher-use-cases-00

Abstract

   Content publishers are increasingly using multiple CDNs to publish
   content to the consumers. It is important to take into account their
   specific requirements with respect to workflow restrictions with
   respect to content licensing rules. Also, certain content
   applications have specific delivery requirements that need to
   considered while negotiating or signaling inter-CDN arrangements.
   This contribution highlights some of these use cases to help motivate
   discussion.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on July 30, 2011.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the



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   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   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.








































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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 4
      1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . 4
   2.  CDNI Model and CDNI APIs  . . . . . . . . . . . . . . . . . . . 5
   3.  Workflow Management Use Cases . . . . . . . . . . . . . . . . . 7
      3.1.  Asymmetric Content Availability Use Case . . . . . . . . . 7
      3.2.   Content Purge Use Case  . . . . . . . . . . . . . . . . . 7
      3.3.   Service Level Agreement Negotiation Use Case  . . . . . . 8
   4.  Detailed Content Delivery Use Cases . . . . . . . . . . . . . . 8
      4.1.  Grouped File Delegation  . . . . . . . . . . . . . . . . . 8
      4.2.  Adaptive Bitrate Streaming Use Case  . . . . . . . . . . . 9
      4.3   Session Shifting Use Case  . . . . . . . . . . . . . . . . 9
      4.4   Origin Server Failover Use Case  . . . . . . . . . . . .  10
   5. Conclusions  . . . . . . . . . . . . . . . . . . . . . . . . .  11
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
      8.1.  Normative References . . . . . . . . . . . . . . . . . .  12
      8.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14





























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1.  Introduction

     Many use cases for CDN Interconnection are discussed in [I-
   D.bertrand-cdni-use-cases] from the viewpoint of the CDSP.  However,
   with the growing popularity of over-the-top (OTT) delivery, many
   content providers (CP) are now choosing to run their own service,
   without operating their own CDN.  The CP may contract and manage
   multiple CDNs, as opposed to selecting an "Authoritative CDN" to
   manage CDN delegation, as described in [I-D.bertrand-cdni-use-cases].
   This draft takes the viewpoint of these CPs using a federation of
   CDNs.

     This document provides additional use cases addressing the needs of
   workflow management agents (WMA), as they manage multiple
   Authoritative CDNs.  More detailed use cases for unique content
   delivery scenarios for CPs and end users (EU) are also provided.

1.1.  Terminology

   This document uses the terminology defined in section 1.1 of
   [I-D.jenkins-cdni-problem-statement] and
   [I-D.bertrand-cdni-use-cases].





























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2.  CDNI Model and CDNI APIs

   For convenience Figure 1 from [I-D.jenkins-cdni-problem-statement]
   illustrating the CDNI problem area and the CDNI APIs is replicated
   below with the addition of the workflow management component.














































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      -------               -------
     /       \             /       \
    |  CSP    |***********|   WMA   |
     \       /             \       /
      -------               -------
         *                   # # #
         *                   # # #
         *                   # # #     /\
         *                   # # #    /  \
      ---------------------  # # #   |CDNI|       ---------------------
     /    Upstream CDN     \ # # #   |    |      /   Downstream CDN    \
     |     +-------------+ | # # # Control API   | +-------------+     |
     |     |CDN Control  |<======#===|====|=======>| CDN Control |     |
     |     +------*-*-*--+ | # #     |    |      | +-*-*-*-------+     |
     |            * * *    | # #     |    |      |   * * *             |
     |     +------*------+ | # #   Logging API   | +-----*-------+     |
     | ****| Logging     |<====#=====|====|=======>|  Logging    |**** |
     | *   --------------+ | #       |    |      | +-------------+   * |
     | *            * *    | #       |    |      |   * *             * |
     | *   +--------*----+ | #   Req-Routing API | +---*---------+   * |
     | * **|Req-Routing  |<==========|====|=======>| Req-Routing |** * |
     | * * +-------------+ | #       |    |      | +-------------+ * * |
     | * *            *    | #       |    |      |   *             * * |
     | * * +----------*--+ | #  CDNI Metadata API| +-*-----------+ * * |
     | * * |Distribution |<==#=======|====|=======>| Distribution| * * |
     | * * |             | |          \  /       | |             | * * |
     | * * | +---------+ | |           \/        | | +---------+ | * * |
     | * ****|         | | |                     | | |         |**** * |
     | ******|Surrogate|*****************************|Surrogate|****** |
     |     | +---------+ | |       Acquisition   | | +-----*---+ |     |
     |     +-------------+ |                     | +-------*-----+     |
     \                     /                     \         *           /
      ---------------------                       ---------*-----------
                                                           *
                                                           * Delivery
                                                           *
                                                        +------+
                                                        | User |
                                                        | Agent|
                                                        +------+

   <==>  interfaces inside the scope of CDNI

   ****  interfaces outside the scope of CDNI

   ####  interfaces important to Workflow Management Agents

                    Figure 1: CDNI Model and CDNI APIs



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3.  Workflow Management Use Cases

   This section identifies generic requirements independent of the
   individual CDNI APIs.  Some of those are expected to affect multiple
   or all APIs.

   Content licensing is typically a complex mixture of temporal
   restrictions (e.g., how soon after the original release date), geo-
   location restrictions (e.g., in which countries), device and quality
   restrictions (e.g., only on devices with resolutions less than WxH),
   and NSP restrictions.

3.1.  Asymmetric Content Availability Use Case


       Often content is tailored to the NSP and devices supported by the
       NSP, e.g., NSP1 only support smart phones but not tablet devices,
       therefore only requires content with resolution less than
       480x320.  In this case, the content files available through the
       CDN (CDN1), operated by the NSP (NSP1), will be a subset of all
       available content files.  A second NSP (NSP2) may support laptop
       and tablet devices and may therefore require higher resolution
       video.  This CDN (CDN2), operated by NSP2, will require access to
       and possibly pre-positioning of different content files than
       CDN1.  The ability to delegate requests from CDN2 to CDN1 is
       diminished by the availability of only a limited subset of the
       content files on CDN1.  In this case, both CDN1 and CDN2 may be
       considered Authoritative CDNs, however, any resiliency measures
       introduced by CDN interconnection will be limited.  The WMA must
       track and manage the rights of each Authoritative CDN to
       different content files and be able to set delegation policies
       for those CDNs.


3.2.   Content Purge Use Case


          Temporal licensing restrictions typically consist of a
        "sunrise" (activation time), a "sunset" (deactivation time), and
        a "takedown" (expiration time).  Sunrise and sunset refer to
        logical availability, however, takedown refers to physical
        availability.  Service agreements must typically support
        takedown guarantees.  The ability to both issue and confirm the
        expunging of content files from surrogates is required to
        enforce these content licenses.  These licenses may have
        different sunrise, sunset, and takedown times for different
        NSPs.  The WMA must track, manage, and confirm the takedown of
        content from each of the Authoritative CDNs that content was



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        provided to. In the case that an Authoritative CDN delegated
        delivery to a non-Authoritative CDN, confirmation of content
        takedown from the non-Authoritative Downstream CDNs must be
        confirmed as well.

3.3.   Service Level Agreement Negotiation Use Case


        For video streaming services, the content provided for
        distribution is typically encoded at known bitrates.  The
        quality of the delivered content is dependent upon the network
        capacity of the CDN.  EU experience is critical to protecting CP
        brand loyalty.  The content provider may wish to restrict
        delivery when insufficient bandwidth exists to deliver a high
        quality content viewing experience.  The "Overload Handling" use
        case, discussed in [I-D.bertrand-cdni-use-cases], discusses
        expansion of bandwidth, but not the specific enforcement of
        minimum bandwidth or minimum latency requirements.  Metadata
        needs to support the specification of these requirements.  The
        WMA needs to be able to negotiate and set limitations for
        content delivery.



4.  Detailed Content Delivery Use Cases

   This section identifies generic requirements independent of the
   individual CDNI APIs.  Some of those are expected to affect multiple
   or all APIs.

4.1.  Grouped File Delegation

        Delegating or pre-positioning content which are commonly
        requested in close temporal proximity is an important use case
        for CDN optimization and affects metadata concepts in CDN
        interconnection.

            For the delivery of streaming video, the content may be
        separated into multiple files, e.g., segment files for HTTP Live
        Streaming (HLS) [I-D.pantos-http-live-streaming].  When
        delegating requests for HLS content, it may not be efficient to
        delegate each segment file request, but rather be able to
        delegate sets of content files  that are commonly requested as a
        group.  Web page images and icons may also fall into this
        category.  For streaming video, however, there is also a
        sequential time component for which metadata may be used to
        optimize paced on-demand pre-fetching of segment files.
        Similarly, for the case of pre-positioning grouped files, the



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        ability to set a priority for certain files (e.g., common video
        starting points or hot-spots) allow the CDN to optimize storage
        usage, while still pre-positioning content critical to
        minimizing initial delivery latency.  This information, combined
        with geo-location information, may enable the CDN to further
        optimize surrogate selection.


4.2.  Adaptive Bitrate Streaming Use Case

        Support for adaptive bitrate delivery an important use case for
        HTTP-based streaming video (e.g., HTTP Live Streaming (HLS)
        [I-D.pantos-http-live-streaming])

            The CDN interconnection problem statement
        [I-D.jenkins-cdni-problem-statement] clearly states as a
        non-goal: "Content preparation, including encoding and
        transcoding".  While the actual transformation of content is
        beyond the scope of CDN interconnection, the understanding about
        the existence of pre-transcoded files which are related to each
        other, is valuable for CDN pre-fetching, pre-positioning, and
        delivery optimization. This may be considered a further
        extension of the Grouped File Delegation use case.  Metadata
        relaying the relative access patterns for specific content
        (e.g., switching from bitrate 6 to bitrate 7 is more likely than
        switching from bitrate 7 to bitrate  1) may be used to further
        optimize storage usage and surrogate selection.

4.3   Session Shifting Use Case


        Session shifting between first (TV), second (PC), and third
        (mobile) screen devices is a primary use case for CDN
        interconnection.

            The "Device and Network Technology Extension" use case,
        discussed in [I-D.bertrand-cdni-use-cases], covers a single
        device moving from one NSP/CDN to another (e.g., switching from
        WiFi to 3G on a mobile device).  An extension to this scenario
        is switching between different devices either within the same
        NSP (e.g., switching from a TV on a cable network, to a PC
        connected to a cable modem or to a mobile device connected via
        WiFi to the cable modem) or across multiple NSPs (e.g., from a
        TV connected to a cable or a PC connected to a cable modem or a
        mobile device connected via WiFi to the cable modem, to a mobile
        device on a 3G/4G cellular connection).  The requests may come
        from different devices and/or access networks, but all belong to
        the same virtual data stream.



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4.4   Origin Server Failover Use Case


            Support for multiple origin servers from which Downstream
        CDNs may retrieve content is an important use case for resilient
        delivery.

            The "Overload Handling" and "Resiliency" use cases,
        discussed in [I-D.bertrand-cdni-use-cases], cover cases where an
        EU is redirected to an alternate CDN (CDN2) when the CDN which
        received the initial request (CDN1) is unable to service it due
        to capacity issues or other failure.  An extension to this
        scenario is the condition where the origin server (OS1) becomes
        either temporarily or permanently unreachable to CDN1.  In this
        case, there are two possible options:

           o Redirect the request to CDN2, in the hope that CDN2 still
           has connectivity to the origin server (OS1).


           o Failover to a secondary origin server (OS2) and attempt to
           retrieve the content from OS2 in order to service the
           request.


            There may be a arbitrary number of alternate origin servers
        (which may in fact be other CDNs) and failover to an alternate
        CDN should only occur after exhausting a possibly limited
        alternate origin server search.  In the case of live streaming
        video, an origin server may go down unexpectedly, and retrieval
        from an alternate CDN may not be feasible if it introduces too
        much latency.



















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5. Conclusions


   This draft introduces some content publisher use cases that need to
   be considered in the CDNI efforts. We covered the cases that apply to
   workflow management as well as content delivery.













































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5.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.


6.  Security Considerations

   Content licensing rights need to be managed across multiple CDN
   domains as described in the workflow management use cases above.

7.  Acknowledgements

   The authors would like to thank the organizers of this effort to
   discuss the requirements for delivering premium content over the
   Internet.

8.  References

8.1.  Normative References

   [I-D.bertrand-cdni-use-cases]
         Bertrand, G. and E. Stephan, G. Watson, T. Burbridge,
         P. Eardley, "Use Cases for Content Distribution Network
         Interconnection", draft-bertrand-cdni-use-cases-01
         (work in progress), January 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-01 (work
              in progress), January 2011.

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

   [I-D.pantos-http-live-streaming]
         R. Pantos, "HTTP Live Streaming",
         draft-pantos-http-live-streaming-05(work in progress),
         November 2011.

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



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   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

8.2.  Informative References

   [Apache-Common]
              "Apache Common Log File Format (http://www.w3.org/Daemon/
              User/Config/Logging.html#common-logfile-format)".

   [Apache-Format]
              "Apache LogFormat Directive (http://httpd.apache.org/docs/
              1.3/mod/mod_log_config.html#logformat)".

   [I-D.amini-cdi-distribution-reqs]
              Amini, L., "Distribution Requirements for Content
              Internetworking", draft-amini-cdi-distribution-reqs-02
              (work in progress), November 2001.

   [I-D.cain-request-routing-req]
              Cain, B., "Request Routing Requirements for Content
              Internetworking", draft-cain-request-routing-req-03 (work
              in progress), November 2001.

   [I-D.gilletti-cdnp-aaa-reqs]
              "CDI AAA Requirements,
              draft-gilletti-cdnp-aaa-reqs-01.txt", June 2001.
























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Authors' Addresses

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

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


   Raj Nair
   Azuki Systems
   43 Nagog Park
   Acton, MA 01720
   USA

   Phone: +1 978-844-5100
   Email: raj.nair@azukisystems.com































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