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Versions: 00 01 02

Internet Engineering Task Force                         G. Bertrand, Ed.
Internet-Draft                                                E. Stephan
Intended status: Informational                   France Telecom - Orange
Expires: April 25, 2013                                   R. Peterkofsky
                                                           Skytide, Inc.
                                                          F. Le Faucheur
                                                           Cisco Systems
                                                            P. Grochocki
                                                           Orange Polska
                                                        October 22, 2012


                         CDNI Logging Interface
                     draft-bertrand-cdni-logging-02

Abstract

   This memo specifies the Logging interface between a downstream CDN
   (dCDN) and an upstream CDN (uCDN) that are interconnected as per the
   CDN Interconnection (CDNI) framework.  First, it describes a
   reference model for CDNI logging.  Then, it specifies the actual
   protocol for CDNI logging information exchange covering the
   information elements as well as the transport of those.

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 April 25, 2013.

Copyright Notice

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

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



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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  6
     1.2.  Abbreviations  . . . . . . . . . . . . . . . . . . . . . .  8
   2.  CDNI Logging Reference Model . . . . . . . . . . . . . . . . .  8
     2.1.  CDNI Logging interactions  . . . . . . . . . . . . . . . .  8
     2.2.  Overall Logging Chain  . . . . . . . . . . . . . . . . . . 13
       2.2.1.  Logging Generation and During-Generation
               Aggregation  . . . . . . . . . . . . . . . . . . . . . 15
       2.2.2.  Logging Collection . . . . . . . . . . . . . . . . . . 15
       2.2.3.  Logging Filtering  . . . . . . . . . . . . . . . . . . 16
       2.2.4.  Logging Rectification and Post-Generation
               Aggregation  . . . . . . . . . . . . . . . . . . . . . 16
       2.2.5.  Log-Consuming Applications . . . . . . . . . . . . . . 17
         2.2.5.1.  Maintenance/Debugging  . . . . . . . . . . . . . . 17
         2.2.5.2.  Accounting . . . . . . . . . . . . . . . . . . . . 17
         2.2.5.3.  Analytics and Reporting  . . . . . . . . . . . . . 18
         2.2.5.4.  Security . . . . . . . . . . . . . . . . . . . . . 18
         2.2.5.5.  Legal Logging Duties . . . . . . . . . . . . . . . 18
         2.2.5.6.  Notions common to multiple Log Consuming
                   Applications . . . . . . . . . . . . . . . . . . . 18
   3.  CDNI Logging Information Structure and Transport . . . . . . . 20
   4.  CDNI Logging Fields  . . . . . . . . . . . . . . . . . . . . . 22
     4.1.  Generic Fields . . . . . . . . . . . . . . . . . . . . . . 22
       4.1.1.  Semantics of Generic CDNI Logging Fields . . . . . . . 22
       4.1.2.  Syntax of Generic CDNI Logging Fields  . . . . . . . . 24
     4.2.  Logging Fields for Content Delivery  . . . . . . . . . . . 25
       4.2.1.  Semantics for Delivery CDNI Logging Fields . . . . . . 25
       4.2.2.  Syntax for Delivery CDNI Logging Fields  . . . . . . . 26
     4.3.  Logging Fields for Content Acquisition . . . . . . . . . . 26
       4.3.1.  Semantics for Acquisition CDNI Logging Fields  . . . . 27
       4.3.2.  Syntax for Acquisition CDNI Logging Fields . . . . . . 27
     4.4.  Logging Fields for Control . . . . . . . . . . . . . . . . 27
     4.5.  Logging Fields for Other Operations  . . . . . . . . . . . 27
   5.  CDNI Logging Records . . . . . . . . . . . . . . . . . . . . . 28
     5.1.  Content Delivery . . . . . . . . . . . . . . . . . . . . . 28
     5.2.  Content Acquisition  . . . . . . . . . . . . . . . . . . . 29
       5.2.1.  Logging Records Provided by dCDN to uCDN . . . . . . . 29
       5.2.2.  Logging Records Provided by uCDN to dCDN . . . . . . . 29
     5.3.  Content Invalidation and Purging . . . . . . . . . . . . . 30
     5.4.  Logging Extensibility  . . . . . . . . . . . . . . . . . . 30
   6.  CDNI Logging File Format . . . . . . . . . . . . . . . . . . . 30
     6.1.  Logging Files  . . . . . . . . . . . . . . . . . . . . . . 31
     6.2.  File Format  . . . . . . . . . . . . . . . . . . . . . . . 31
       6.2.1.  Headers  . . . . . . . . . . . . . . . . . . . . . . . 31
       6.2.2.  Body (Logging Records) Format  . . . . . . . . . . . . 32
       6.2.3.  Footer Format  . . . . . . . . . . . . . . . . . . . . 33



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   7.  CDNI Logging File Transport Protocol . . . . . . . . . . . . . 33
   8.  Logging Control  . . . . . . . . . . . . . . . . . . . . . . . 33
   9.  Open Issues  . . . . . . . . . . . . . . . . . . . . . . . . . 34
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 35
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 35
     11.1. Privacy  . . . . . . . . . . . . . . . . . . . . . . . . . 35
     11.2. Non Repudiation  . . . . . . . . . . . . . . . . . . . . . 35
   12. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 35
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 35
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 35
     13.2. Informative References . . . . . . . . . . . . . . . . . . 36
   Appendix A.  Examples Log Format . . . . . . . . . . . . . . . . . 37
     A.1.  W3C Common Log File (CLF) Format . . . . . . . . . . . . . 37
     A.2.  W3C Extended Log File (ELF) Format . . . . . . . . . . . . 38
     A.3.  National Center for Supercomputing Applications (NCSA)
           Common Log Format  . . . . . . . . . . . . . . . . . . . . 39
     A.4.  NCSA Combined Log Format . . . . . . . . . . . . . . . . . 39
     A.5.  NCSA Separate Log Format . . . . . . . . . . . . . . . . . 39
     A.6.  Squid 2.0 Native Log Format for Access Logs  . . . . . . . 40
   Appendix B.  Requirements  . . . . . . . . . . . . . . . . . . . . 41
     B.1.  Additional Requirements  . . . . . . . . . . . . . . . . . 41
     B.2.  Compliancy with Requirements draft . . . . . . . . . . . . 42
   Appendix C.  CDNI WG's position on candidate protocols for
                Logging Transport . . . . . . . . . . . . . . . . . . 42
     C.1.  CDNI WG's position on Syslog . . . . . . . . . . . . . . . 42
     C.2.  CDNI WG's position on SNMP . . . . . . . . . . . . . . . . 42
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 42
























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1.  Introduction

   This memo specifies the Logging interface between a downstream CDN
   (dCDN) and an upstream CDN (uCDN).  First, it describes a reference
   model for CDNI logging.  Then, it specifies the actual protocol for
   CDNI logging information exchange covering the information elements
   as well as the transport of those.

   The reader should be familiar with the work of the CDNI WG:

   o  CDNI problem statement [RFC6707] and framework
      [I-D.ietf-cdni-framework] identify a Logging interface,

   o  Section 7 of [I-D.ietf-cdni-requirements] specifies a set of
      requirements for Logging,

   o  [I-D.ietf-cdni-use-cases] outlines real world use-cases for
      interconnecting CDNs.  These use cases require the exchange of
      Logging information between the dCDN and the uCDN.

   As stated in [RFC6707], "the CDNI Logging interface enables details
   of logs or events to be exchanged between interconnected CDNs".

   The present document describes:

   o  The CDNI Logging reference model (Section 2),

   o  The CDNI Logging information structure and Transport (Section 3),

   o  The CDNI Logging Fields (Section 4),

   o  The CDNI Logging Records (Section 5),

   o  The CDNI Logging File format (Section 6),

   o  The CDNI Logging File Transport Protocol (Section 7),

   o  and, finally, the description of the CDNI Logging Control that is
      to be supported by the CDNI Control Interface Section 8.

   In the Appendices, the document provides:

   o  A list of identified requirements (Appendix B.1), which should be
      considered for inclusion in [I-D.ietf-cdni-requirements],







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1.1.  Terminology

   In this document, the first letter of each CDNI-specific term is
   capitalized.  We adopt the terminology described in [RFC6707] and
   [I-D.ietf-cdni-framework], and extend it with the additional terms
   defined below.

   For clarity, we use the word "Log" only for referring to internal CDN
   logs and we use the word "Logging" for any inter-CDN information
   exchange and processing operations related to the CDNI Logging
   interface.  Log and Logging formats may be different.

   Log: CDN internal information collection and processing operations.

   Logging: Inter-CDN information exchange and processing operations.

   CDNI Logging Field: an atomic element of information that can be
   included in a CDNI Logging Record.  The time an event/task started,
   the IP address of an End user to whom content was delivered, and the
   URI of the content delivered are examples of CDNI logging fields.

   CDNI Logging Record: an information record providing information
   about a specific event.  This comprises a collection of CDNI Logging
   Fields.

   Separator Character: a specific character used to enable the parsing
   of Logging Records.  This character separates the Logging Fields that
   compose a Logging Record.

   Logging File: a file containing Logging Records and additional
   information for easing the processing of the Logging Records.

   CDN Reporting: the process of providing the relevant information that
   will be used to create a formatted content delivery report provided
   to the CSP in deferred time.  Such information typically includes
   aggregated data that can cover a large period of time (e.g., from
   hours to several months).  Uses of Reporting include the collection
   of charging data related to CDN services and the computation of Key
   Performance Indicators (KPIs).

   CDN Monitoring: the process of providing content delivery information
   in real-time.  Monitoring typically includes data in real time to
   provide visibility of the deliveries in progress, for service
   operation purposes.  It presents a view of the global health of the
   services as well as information on usage and performance, for network
   services supervision and operation management.  In particular,
   monitoring data can be used to generate alarms.




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   End-User experience management: study of Logging data using
   statistical analysis to discover, understand, and predict user
   behavior patterns.

   Class-of-requests: A Class-of-requests identifies a set of content
   Requests, related to a specific CSP, received from clients in a given
   footprint and sharing common properties.  These properties include:

   o  Any header, URL parameter, query parameter of an HTTP (or RTMP)
      content request

   o  Any header, or sub-domain of the FQDN of a DNS lookup request

   Examples:

   o  Class-of-Requests = all the requests that include the HTTP header
      "User-Agent: Mozilla/5.0" related to CSP
      "http://*.cdn.example.com" from AS3215

   o  Class-of-Requests = all the DNS requests from anywhere and related
      to CSP "cdn*.example.com"

   Delivery Service: A Delivery Service is defined by a set of Class-of-
   Requests and a list of parameters that apply to all these Class-of-
   Requests (logging format, delivery quality/capabilities
   requirements...)

   Service Agreement: A service agreement is defined by a uCDN
   identifier, a dCDN identifier, a set of Delivery Services and a list
   of parameters that apply to the Service Agreement.

   Once a Service Agreement is agreed between the administrative
   entities managing the CDNs to be interconnected, the upstream CDN and
   the downstream CDN of the CDNI interconnection must be configured
   according to this agreed Service Agreement.  For instance, a given
   uCDN (uCDN1) may request a given dCDN (dCDN1) to configure one
   Delivery Service for handling requests for HTTP Adaptive streaming
   videos delegated by uCDN1 and related to a specific CSP (CSP1) and
   another one for handling requests for static pictures delegated by
   uCDN1 and related to CSP1.  These Delivery services would belong to
   the Service Agreement between uCDN1 and dCDN1 for CSP1.  In this
   simple example, uCDN1 may request dCDN1 to include Delivery Service
   information in its CDNI Logging, to help uCDN1 to provide relevant
   reports to CSP1.







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1.2.  Abbreviations

   o  API: Application Programming Interface

   o  CCID: Content Collection Identifier

   o  CDN: Content Delivery Network

   o  CDNP: Content Delivery Network Provider

   o  CoDR: Content Delivery Record

   o  CSP: Content Service Provider

   o  DASH: Dynamic Adaptive Streaming over HTTP

   o  dCDN: downstream CDN

   o  FTP: File Transfer Protocol

   o  HAS: HTTP Adaptive Streaming

   o  KPI: Key Performance Indicator

   o  PVR: Personal Video Recorder

   o  SID: Session Identifier

   o  SFTP: SSH File Transfer Protocol

   o  SNMP: Simple Network Management Protocol

   o  uCDN: upstream CDN


2.  CDNI Logging Reference Model

2.1.  CDNI Logging interactions

   The CDNI logging reference model between a given uCDN and a given
   dCDN involves the following interactions:

   o  control by the uCDN of the logging to be performed by the dCDN
      (e.g. control of which logging fields are to be communicated to
      the uCDN for a given task performed by the dCDN, control of which
      types of events are to be logged).  This is supported by the CDNI
      Control interface.




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   o  generation and collection by the dCDN of logging information
      related to the completion of any task performed by the dCDN on
      behalf of the uCDN (e.g. delivery of the content to an end user)
      or related to events happening in the dCDN that are relevant to
      the uCDN (e.g. failures or unavailability in dCDN).  This takes
      place within the dCDN and does not directly involve CDNI
      interfaces.

   o  communication by the dCDN to the uCDN of the logging information
      collected by the dCDN relevant to the uCDN.  This is supported by
      the CDNI Logging interface.  For example, the uCDN may use this
      logging information to charge the CSP, to perform analytics and
      mornitoring for operational reasons, to provide analytics and
      monitoring views on its content delivery to the CSP, or to perform
      troubleshooting.

   o  control by the dCDN of the logging to be performed by the uCDN on
      behalf of the dCDN.  This is supported by the CDNI Control
      interface.

   o  generation and collection by the uCDN of logging information
      related to the completion of any task performed by the uCDN on
      behalf of the dCDN (e.g. serving of content by uCDN to dCDN for
      acquisition purposes by dCDN) or related to events happening in
      the uCDN that are relevant to the dCDN.  This takes place within
      the uCDN and does not directly involve CDNI interfaces.

   o  communication by the uCDN to the dCDN of the logging information
      collected by the uCDN relevant to the dCDN.  This is supported by
      the CDNI Logging interface.  For example, the dCDN may use this
      logging information for security auditing or content acquisition
      troubleshooting.

   Figure 1 provides an example of CDNI Logging interactions in a
   particular scenario where 4 CDNs are involved in the delivery of
   content from a given CSP: the uCDN has a CDNI interconnection with
   dCDN1 and dCDN2.  In turn, dCDN2 has a CDNI interconnection with
   dCDN3. uCDN, dCDN1, dCDN2 and dCDN3 deliver content for the CSP.  In
   this example, the CDNI Logging interface enables the uCDN to obtain
   logging information from all the dCDNs involved in the delivery.  In
   the example, uCDN uses the Logging data:

   o  to analyze the performance of the delivery operated by the dCDNs
      and to adjust its operations (e.g., request routing) as
      appropriate

   o  to provide reporting (non-real time) and monitoring (real time)
      information to CSP.



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   For instance, uCDN merges Logging data, extracts relevant KPIs, and
   presents a formatted report to CSP, in addition to a bill for the
   content delivered by uCDN itself or its dCDNs on his behalf. uCDN may
   also provide Logging data as raw log files to CSP, so that CSP can
   use its own Logging analysis tools.


                   +-----+
                   | CSP |
                   +-----+
                      ^ Reporting and monitoring data
                      * Billing
                   ,--*--.
       Logging  ,-'       `-.
       Data  =>(     uCDN    )<=   Logging
          //   `-.       _,-'   \\  Data
          ||        `-'-'-'      ||
       ,--v--.       ^ ^       ,--v--.
    ,-'       `-.    + +    ,-'       `-.
   (   dCDN-1    )<+++ +++>(   dCDN-2    )<==   Logging
    `-.       ,-'  Logging  `-.      _,-'    \\ Data
      `--'--'       Control    `--'-'        ||
                                  ^       ,--v--.
                          Logging +     ,'       `-.
                           Control++++>(  dCDN-3    )
                                        `.       ,-'
                                          `--'--'

   <====> CDNI Logging Interface
   <++++> CDNI Control Interface
   ***> outside the scope of CDNI


          Figure 1: Interactions in CDNI Logging Reference Model

   A dCDN (e.g. dCDN-2) integrates the relevant logging data obtained
   from its dCDNs (e.g. dCDN-3) in the logging data that it provides to
   the uCDN, so that the uCDN ultimately obtains all logging information
   relevant to a CSP for which it acts as the authoritative CDN.

   Note that the format of Logging data that a CDN provides over the
   CDNI interface might be different from the one that the CDN uses
   internally.  In this case, the CDN needs to reformat the Logging data
   before it provides this data to the other CDN over the CDNI Logging
   interface.  Similarly, a CDN might reformat the Logging data that it
   receives over the CDNI Logging interafce before injecting it into its
   log-consuming applications or before providing some of this logging
   information to the CSP.  Such reformatting operations introduce



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   latency in the logging distribution chain and introduce a processing
   burden.  Therefore, there are benefits in specifying CDNI Logging
   format that are as close as possible from the CDN Log formats
   commonly used in CDNs today.

   Figure 2 maps the CDNI Logging interactions discussed above onto the
   CDNI Reference Model defined in [RFC6707].












































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     --------
    /        \
    |   CSP  |
    \        /
     --------
         *
         * Reporting, Monitoring,
         * Billing                 /\
         *                        /  \
     ----------------------      |CDNI|        ----------------------
    /     Upstream CDN     \     |    |       /    Downstream CDN    \
    |      +-------------+ | Control Interface| +-------------+      |
    |      +             + | (Logging Control)| |             |      |
    |*******   Control   |<++++++|++++|++++++>|   Control   *******|
    |*     +------*----*-+ |     |    |       | +-*----*------+     *|
    |*            *    *   |     |    |       |   *    *            *|
    |*     +------*------+ | Logging Interface| +------*------+     *|
    |*     +             + | (Logging Data )  | |             |     *|
    |* *****   Logging   |<======|====|========>|   Logging   ***** *|
    |* *   +-*-----------+ |     |    |       | +-----------*-+   * *|
    |* *     *         *   |     |    |       |   *         *     * *|
  .....*...+-*---------*-+ |     |    |       | +-*---------*-+...*.*...
  . |* * *** Req-Routing | |     |    |       | | Req-Routing *** * *| .
  . |* * * +-------------+.|     |    |       | +-------------+ * * *| .
  . |* * *                 .     |    |       |                 * * *| .
  . |* * * +-------------+ |.    |    |       | +-------------+ * * *| .
  . |* * * | Distribution| | .   |    |       | | Distribution| * * *| .
  . |* * * |             | |  .   \  /        | |             | * * *| .
  . |* * * |+---------+  | |   .   \/         | |  +---------+| * * *| .
  . |* * ***| +---------+| |    ....Request......+---------+ |*** * *| .
  . |* *****+-|Surrogate|************************|Surrogate|-+***** *| .
  . |*******  +---------+| |   Acquisition    | |+----------+ *******| .
  . |      +-------------+ |                  | +-------*-----+      | .
  . \                      /                  \         *            / .
  .  ----------------------                    ---------*------------  .
  .                                                     *              .
  .                                                     * Delivery     .
  .                                                     *              .
  .                                                  +--*---+          .
  ...............Request.............................| User |..Request..
                                                     | Agent|
                                                     +------+

  <====> CDNI Logging Interface
  <++++> CDNI Control Interface
  ****  interfaces outside the scope of CDNI
  ....  interfaces outside the scope of CDNI




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   Figure 2: Mapping of CDNI Logging interactions on the CDNI Reference
                                   Model

   As illustrated in Figure 2, the Logging Control (including signaling
   of which logging fields are to be communicated across CDNs for a
   given task) occurs over the Control Interface level.  The rationale
   for using the Control interface for Logging Control (instead of for
   instance using the Metadata interface) includes:

   o  the Logging Control interactions typically define fairly static
      information for initializing and controlling the Logging
      interface, which matches the role of the Control Interface as
      described in [I-D.ietf-cdni-framework] and [RFC6707].

   o  the Logging Control information (specifying the Logging
      information format and scope is primarily intended to be consumed
      by the (typically fairly centralized) logical entity responsible
      for collecting intra-CDN logs, processing, filtering those and
      then exporting the relevant subset of logs/fields to the other
      CDNs.

   o  the surrogates within a given CDN are typically not expected to
      need to be aware of the specific set of fields or set of events
      that have been requested by various interconnected CDNs.  Rather
      the surrogates are likely to perform some generic logging for all
      services regardless of the peculiarities of every CDNI agreement.
      Processing (e.g. filtering, format adaptation) of the generic
      logging information generated by the Surrogates is expected to
      take place to ensure that each interconnected CDN receives the
      specific set of fields and logs it has requested through Logging
      Control.  Therefore there is no need to ensure that the Logging
      control information be easily distributable through the CDNs right
      down to surrogates.

   o  the Control interface is expected to support the capability to
      apply control at the granularity of content sets (e.g. for content
      Purge) which is required for Logging Control since it is expected
      that a CDN may require different sets of logging fields and events
      for different sets of content (e.g. because it only needs to
      perform coarse billing for a given CSP while it needs to provide
      detailed analytics for another CSP).

2.2.  Overall Logging Chain

   This section discusses the overall logging chain within and across
   CDNs to clarify how CDN Logging information is expected to fit in
   this overall chain.  Figure 3 illustrates the overall logging chain
   within the dCDN, across CDNs using the CDNI Logging interface and



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   within the uCDN.  For readability, the Figure only considers logging
   information flowing from the dCDN to the uCDN.  Note that the logging
   chain illustrated in the Figure is obviously only indicative and
   varies in specific environments.  For example, there may be more or
   less instantiations of each entity (ie there may be 4 Log consuming
   applications in a given CDN.  As another example, there may be one
   instance of Rectification process per Log Consuming Application
   instead of a shared one.

             Log Consuming    Log Consuming
                 App              App
                 /\              /\
                 |               |
           Rectification--------
           /\
           |
           Filtering
            /\
            |
        Collection                        uCDN
        /\       /\
        |        |
        |     Generation
        |
   CDNI Logging ---------------------------------------------
   exchange
        /\         Log Consuming    Log Consuming
        |                 App              App
        |                  /\              /\
        |                  |               |
   Rectification     Rectification---------
           /\       /\
           |        |
           Filtering
            /\
            |
         Collection                         dCDN
         /\       /\
         |        |
   Generation    Generation



            Figure 3: CDNI Logging in the overall Logging Chain

   The following subsections describe each of the processes potentially
   involved in the logging chain of Figure 3.




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2.2.1.  Logging Generation and During-Generation Aggregation

   CDNs typically generate logging information for all significant task
   completions, events, and failures.  Logs are typicallly generated by
   many devices in the CDN including the surrogates, the request routing
   system, and the control system.

   The amoung of Logging information generated can be huge.  Therefore,
   during contract negotiations, interconnected CDNs often agree on a
   Logging retention duration, and optionally, on a maximum size of the
   Logging data that the dCDN must keep.  If this size is exceeded, the
   dCDN must alert the uCDN but may not keep more Logs for the
   considered time period.  In addition, CDNs may aggregate logs and
   transmit only summaries for some categories of operations instead of
   the full Logging data.  Note that such aggregation leads to an
   information loss, which may be problematic for some usages of Logging
   (e.g., debugging).

   [I-D.brandenburg-cdni-has] discusses logging for HTTP Adaptive
   Streaming (HAS).  In accordance with the recommendations articulated
   there, it is expected that a surrogate will generate separate logging
   information for delivery of each chunk of HAS content.  This ensures
   that separate logging information can then be provided to
   interconnected CDNs over the CDNI Logging interface.  Still in line
   with the recommendations of [I-D.brandenburg-cdni-has], the logging
   information for per-chunck delivery may include some information (a
   Content Collection IDentifier and a Session IDentifier as discussed
   in Section 4.1.1) intended to facilitate subsequent post-generation
   aggregation of per-chunk logs into per-session logs.  Note that a CDN
   may also elect to generate aggregate per-session logs when performing
   HAS delivery, but this needs to be in addition to, and not instead
   of, the per-chunk delivery logs.  We note that this may be revisited
   in future versions of this document.

2.2.2.  Logging Collection

   This is the process that continuously collects logs generated by the
   log-generating entities within a CDN.

   In a CDNI environment, in addition to collecting logging information
   from log-generating entities within the local CDN, the Collection
   process also collects logging information provided by another CDN, or
   other CDNs, through the CDNI Logging interface.  This is illustrated
   in Figure 3 where we see that the Collecton process of the uCDN
   collects logging information from log-generating entities within the
   uCDN as well as logging information coming through CDNI Logging
   exchange with the dCDN through the CDNI Logging interface.




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2.2.3.  Logging Filtering

   A CDN may require to only present different subset of the whole
   logging information collected to various log-consuming applications.
   This is achieved by the Filtering process.

   In particular, the Filtering process can also filter the right subset
   of information that needs to be provided to a given interconnected
   CDN.  For example, the filtering process in the dCDN can be used to
   ensure that only the logging information related to tasks performed
   on behalf of a given uCDN are made available to that uCDN (thereby
   filtering all the logging information related to deliveries by the
   dCDN of content for its own CSPs).  Similarly, the Filtering process
   may filter or partially mask some fields, for example, to protect End
   Users' privacy when communicating CDNI Logging information to another
   CDN.  Filtering of logging information prior to communication of this
   information to other CDNs via the CDNI Logging interface requires
   that the downstream CDN can recognize the set of log records that
   relate to each interconnected CDN.

   The CDN will also filter some internal scope information such as
   information related to its internal alarms (security, failures, load,
   etc).

   In some use cases described in [I-D.ietf-cdni-use-cases], the
   interconnected CDNs do not want to disclose details on their internal
   topology.  The filering process can then also filter confidential
   data on the dCDNs' topology (number of servers, location, etc.).  In
   particular, information about the requests served by every Surrogate
   may be confidential.  Therefore, the Logging information must be
   protected so that data such as Surrogates' hostnames is not disclosed
   to the uCDN.  In the "Inter-Affiliates Interconnection" use case,
   this information may be disclosed to the uCDN because both the dCDN
   and the uCDN are operated by entities of the same group.

2.2.4.  Logging Rectification and Post-Generation Aggregation

   If Logging is generated periodically, it is important that the
   sessions that start in one Logging period and end in another are
   correctly reported.  If they are reported in the starting period,
   then the Logging of this period will be available only after the end
   of the session, which delays the Logging generation.

   A Logging rectification/update mechanism could be useful to reach a
   good trade-off between the Logging generation delay and the Logging
   accuracy.  Depending on the selected Logging protocol(s), such
   mechanism may be invaluable for real time Logging, which must be
   provided rapidly and cannot wait for the end of operations in



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   progress.

   In the presence of HAS, some log-consuming applications can benefit
   from aggregate per-session logs.  For example, for analytics, per-
   session logs allow display of session-related trends which are much
   more meaningful for some types of analysis than chunk-related trends.
   In the case where the log-generating entities have generated during-
   generation aggregate logs, those can be used by the applications.  In
   the case where aggregate logs have not been generated, the
   Rectification process can be extended with a Post-Generation
   Aggregation process that generates per-session logs from the per-
   chunk logs, possibly leveraging the information included in the per-
   chunk logs for that purpose (Content Collection IDentifier and a
   Session IDentifier).  However, in accordance with
   [I-D.brandenburg-cdni-has], this document does not define exchange of
   such aggregate logs on the CDNI Logging interface.  We note that this
   may be revisited in future versions of this document.

2.2.5.  Log-Consuming Applications

2.2.5.1.  Maintenance/Debugging

   Logging is useful to permit the detection (and limit the risk) of
   content delivery failures.  In particular, Logging facilitates the
   resolution of configuration issues.

   To detect faults, Logging must enable the reporting of any CDN
   operation success and failure, such as request redirection, content
   acquisition, etc.  The uCDN can summarize such information into KPIs.
   For instance, Logging format should allow the computation of the
   number of times during a given epoch that content delivery related to
   a specific service succeeds/fails.

   Logging enables the CDN providers to identify and troubleshoot
   performance degradations.  In particular, Logging enables the
   communication of traffic data (e.g., the amount of traffic that has
   been forwarded by a dCDN on behalf of an uCDN over a given period of
   time), which is particularly useful for CDN and network planning
   operations.

2.2.5.2.  Accounting

   Logging is essential for accounting, to permit inter-CDN billing and
   CSP billing by uCDNs.  For instance, Logging enables the uCDN to
   check the total amount of traffic delivered by every dCDN and for
   every Delivery Service, as well as, the associated bandwidth usage
   (e.g., peak, 95th percentile), and the maximum number of simultaneous
   sessions over a given period of time.



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2.2.5.3.  Analytics and Reporting

   The goal of analytics is to gather any relevant information to track
   audience, analyze user behavior, and monitor the performance and
   quality of content delivery.  For instance, Logging enables the CDN
   providers to report on content consumption (e.g., delivered sessions
   per content) in a specific geographic area.

   The goal of reporting is to gather any relevant information to
   monitor the performance and quality of content delivery and allow
   detection of delivery issues.  For instance, reporting could track
   the average delivery throughput experienced by End Users in a given
   region for a specific CSP or content set over a period of time.

2.2.5.4.  Security

   The goal of security is to prevent and monitor unauthorized access,
   misuse, modification, and denial of access of a service.  A set of
   information is logged for security purposes.  In particular, a record
   of access to content is usually collected to permit the CSP to detect
   infringements of content delivery policies and other abnormal End
   User behaviors.

2.2.5.5.  Legal Logging Duties

   Depending on the country considered, the CDNs may have to retain
   specific Logging information during a legal retention period, to
   comply with judicial requirements.

2.2.5.6.  Notions common to multiple Log Consuming Applications

2.2.5.6.1.  Logging Information Views

   Within a given log-consuming application, different views may be
   provided to differnet users depending on privacy, business, and
   scalability constraints.

   For example, an analytics tool run by the uCDN can provide one view
   to an uCDN operator that exploits all the logging information
   available to the uCDN, while the tool may provide a different view to
   each CSP exploiting only the logging information related to the
   content of the given CSP.

   As another example, maintenance and debugging tools may provide
   different views to different CDN operators, based on their
   operational role.





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2.2.5.6.2.  Key Performance Indicators (KPIs)

   This section presents, for explanatory purposes, a non-exhaustive
   list of Key Performance Indicators (KPIs) that can be extracted/
   produced from logs.

   Multiple log-consuming applications, such as analytics, monitoring,
   and maintenance applications, often compute and track such KPIs.

   In a CDNI environment, depending on teh situation, these KPIs may be
   computed by the uCDN or by the dCDN.  But it is usually the uCDN that
   computes KPIs, because uCDN and dCDN may have different definitions
   of the KPIs and the computation of some KPIs requires a vision of all
   the deliveries performed by the uCDN and all its dCDNs.

   Here is a list of important examples of KPIs:

   o  Number of delivery requests received from End Users in a given
      region for each piece of content, during a given period of time
      (e.g., hour/day/week/month)

   o  Percentage of delivery successes/failures among the aforementioned
      requests

   o  Number of failures listed by failure type (e.g., HTTP error code)
      for requests received from End Users in a given region and for
      each piece of content, during a given period of time (e.g., hour/
      day/week/month)

   o  Number and cause of premature delivery termination for End Users
      in a given region and for each piece of content, during a given
      period of time (e.g., hour/day/week/month)

   o  Maximum and mean number of simultaneous sessions established by
      End Users in a given region, for a given Delivery Service, and
      during a given period of time (e.g., hour/day/week/month)

   o  Volume of traffic delivered for sessions established by End Users
      in a given region, for a given Delivery Service, and during a
      given period of time (e.g., hour/day/week/month)

   o  Maximum, mean, and minimum delivery throughput for sessions
      established by End Users in a given region, for a given Delivery
      Service, and during a given period of time (e.g., hour/day/week/
      month)

   o  Cache-hit and byte-hit ratios for requests received from End Users
      in a given region for each piece of content, during a given period



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      of time (e.g., hour/day/week/month)

   o  Top 10 of the most popularly requested content (during a given
      day/week/month),

   o  Terminal type (mobile, PC, STB, if this information can be
      acquired from the browser type header, for example).

   Additional KPIs can be computed from other sources of information
   than the Logging -- for instance, data collected by a content portal
   or by specific client-side APIs.  Such KPIs are out of scope for the
   present memo.

   The KPIs used depend strongly on the considered log-consuming
   application -- the CDN operator may be interested in different
   metrics than the CSP is.  In particular, CDN operators are often
   interested in delivery and acquisition performance KPIs, information
   related to Surrogates' performance, caching information to evaluate
   the cache-hit ratio, information about the delivered file size to
   compute the volume of content delivered during peak hour, etc.

   Some of the KPIs, for instance those providing an instantaneous
   vision of the active sessions for a given CSP's content, are useful
   especially if they are provided in real time.  By contrast, some
   other KPIs, such as those averaged over a long period of time, can be
   provided in non-real time.


3.  CDNI Logging Information Structure and Transport

   As defined in Section 1.1 a CDNI logging field is as an atomic
   logging information element and a CDNI Logging Record is a collection
   of CDNI Logging Fields containing all logging information
   corresponding to a single logging event.

   This document defines non-real time transport of CDNI Logging
   information over the CDNI interface.  For such non-real time
   transport, this document defines a third level of structure, the CDNI
   Logging File, that is a collection of CDNI Logging Records.  This
   structure is described in Figure 4.  This document then specifies how
   to transport such CDNI Files across interconnected CDNs.  We observe
   that this approach can be tuned in a real deployment to achieve near-
   real time exchange of CDNI Logging information, e.g. by increasing
   the frequency of logging file creation and distribution throughout
   the Logging chain, but it is not expected that this approach can
   support real time transport (e.g. sub-second) of CDNI logging
   information.




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   +------------------------------------------------------+
   |CDNI Logging File                                     |
   |                                                      |
   | +--------------------------------------------------+ |
   | |CDNI Logging Record                               | |
   | |  +-------------+ +-------------+ +-------------+ | |
   | |  |CDNI Logging | |CDNI Logging | |CDNI Logging | | |
   | |  |   Field     | |   Field     | |   Field     | | |
   | |  +-------------+ +-------------+ +-------------+ | |
   | +--------------------------------------------------+ |
   |                                                      |
   | +--------------------------------------------------+ |
   | |CDNI Logging Record                               | |
   | |  +-------------+ +-------------+ +-------------+ | |
   | |  |CDNI Logging | |CDNI Logging | |CDNI Logging | | |
   | |  |   Field     | |   Field     | |   Field     | | |
   | |  +-------------+ +-------------+ +-------------+ | |
   | +--------------------------------------------------+ |
   |                                                      |
   | +--------------------------------------------------+ |
   | |CDNI Logging Record                               | |
   | |  +-------------+ +-------------+ +-------------+ | |
   | |  |CDNI Logging | |CDNI Logging | |CDNI Logging | | |
   | |  |   Field     | |   Field     | |   Field     | | |
   | |  +-------------+ +-------------+ +-------------+ | |
   | +--------------------------------------------------+ |
   +------------------------------------------------------+


                   Figure 4: Structure of Logging Files

   It is expected that future version of this document will also specify
   real time transport of CDNI Logging information over the CDNI
   interface.  We note that this might involve direct transport of CDNI
   Logging Records without prior grouping into a file structure to avoid
   the latency associated with creating and transporting such a file
   structure throughout the logging chain.

   The semantics and encoding of the CDNI Logging fields are specified
   in Section 4.  The semantics and encoding of CDNI Records are
   specified in Section 5.  The CDNI Logging File format is specified in
   Section 6.  The protocol for transport of CDNI Logging File is
   specified in Section 7.








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4.  CDNI Logging Fields

   Existing CDNs Logging functions collect and consolidate logs
   performed by their Surrogates.  Surrogates usually store the logs
   using a format derived from Web servers' and caching proxies' log
   standards such as W3C, NCSA [ELF] [CLF], or Squid format [squid].  In
   practice, these formats are adapted to cope with CDN specifics.
   Appendix A presents examples of commonly used log formats.

4.1.  Generic Fields

   This section specifies a set of generic CDNI Logging Fields that are
   expected to be found in multiple types of CDNI Logging records.

4.1.1.  Semantics of Generic CDNI Logging Fields

   The semantics of the generic CDNI Logging Fields are specified in
   Table 1.

   +------------+------------------------------------------------------+
   | Name       | Description                                          |
   +------------+------------------------------------------------------+
   | Start-time | A start date and time associated with a logged       |
   |            | event; for instance, the time at which a Surrogate   |
   |            | received a content delivery request or the time at   |
   |            | which an origin server received a content            |
   |            | acquisition request.                                 |
   | End-time   | An end date and time associated with a logged event. |
   |            | For instance, the time at which a Surrogate          |
   |            | completed the handling of a content delivery request |
   |            | (e.g., end of delivery or error).                    |
   | Duration   | The duration of an operation in milliseconds.  For   |
   |            | instance, this field could be used to provide the    |
   |            | time it took the Surrogate to send the requested     |
   |            | file to the End-User or the time it took the         |
   |            | Surrogate to acquire the file on a cache-miss event. |
   |            | In the case where Start-time, End-time, and Duration |
   |            | appear in a Logging Record, the Duration is to be    |
   |            | interpreted as a total activity time related to the  |
   |            | logged operation.                                    |
   | Client-IP  | The IP address of the User Agent that issued the     |
   |            | logged request or of a proxy, for instance           |
   |            | "203.0.113.1".                                       |
   | Client-por | The source port of the logged request (e.g., 9542)   |
   | t          |                                                      |
   | Destinatio | The IP address of the host that received the logged  |
   | n-IP       | request (e.g., 192.0.2.2).                           |




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   | Destinatio | The destination port of the logged request (e.g.,    |
   | n-port     | 80).                                                 |
   | Operation  | The kind of operation that is logged; for instance,  |
   |            | Acquisition, Delivery, or Purging.                   |
   | URI_full   | The full requested URL (e.g.,                        |
   |            | "http://node1.peer-a.op-b.net/cdn.csp.com/movies/pot |
   |            | ter.avi?param=11&user=toto").  When HTTP request     |
   |            |  redirection is used, this URI includes the Surrogat |
   |            | eFQDN.  If the association of requests to Surrogates |
   |            |  is confidential, the dCDN can present only URI_part |
   |            |  to uCDN.                                            |
   | URI_part   | The requested URL path (e.g.,                        |
   |            | /cdn.csp.com/movies/potter.avi?param=11&user=toto if |
   |            | the full request URL was                             |
   |            | "http://node1.peer-a.op-b.net/cdn.csp.com/movies/pot |
   |            | ter.avi?param=11&user=toto").  The URI without       |
   |            |  host-name typically includes the "CDN domain"       |
   |            |  (ex.cdn.csp.com) - cf. [I-D.ietf-cdni-framework]: i |
   |            | tenables the identification of the CSP service agree |
   |            | dbetween the CSP and the CDNP operating the uCDN.    |
   | Protocol   | The protocol and protocol version of the message     |
   |            | that triggered the Logging entry (e.g., HTTP/1.1).   |
   | Request-me | The protocol method of the request message that      |
   | thod       | triggered the Logging entry.                         |
   | Status     | The protocol method of the reply message related to  |
   |            | the Logging entry                                    |
   | Bytes-Sent | The number of bytes at application-layer             |
   |            | protocol-level (e.g., HTTP) of the reply message     |
   |            | related to the Logging entry.  It includes the size  |
   |            | of the response headers.                             |
   | Headers-Se | The number of bytes corresponding to response        |
   | nt         | headers at application-layer protocol-level (e.g.,   |
   |            | HTTP) of the reply message related to the Logging    |
   |            | entry.                                               |
   | Bytes-rece | The number of bytes (headers + body) of the message  |
   | ived       | that triggered the Logging entry.                    |
   | Referrer   | The value of the Referrer header in an HTTP request. |
   | User-Agent | The value of the User Agent header in an HTTP        |
   |            | request.                                             |
   | Cookie     | The value of the Cookie header in an HTTP request.   |
   | Byte-Range | [Ed. note: to be defined]                            |
   | Cache-cont | The value of the cache-control header in an HTTP     |
   | rol        | answer.  This header is particularly important for   |
   |            | content acquisition logs.                            |
   | Record-dig | A digest of the Logging Record; it enables detecting |
   | est        | corrupted Logging Records.                           |





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   | CCID       | A Content Collection IDentifier (CCID) eases the     |
   |            | correlation of several Logging Records related to a  |
   |            | Content Collection (e.g., a movie split in chunks).  |
   | SID        | A Session Identifier (SID) eases the correlation     |
   |            | (and aggregation) of several Logging Records related |
   |            | to a session.  The SID is especially relevant for    |
   |            | summarizing HAS Logging information                  |
   |            | [I-D.brandenburg-cdni-has].                          |
   +------------+------------------------------------------------------+

             Table 1: Semantics of Generic CDNI Logging Fields

   NB: we define three fields related to the timing of logged
   operations: Start-time, End-time, and Duration.  Start-time is
   typically useful for human readers (e.g., while debugging), however,
   some servers log the operation's End-time which corresponds to the
   time of log record generation.  In absence of Logging summarization,
   only two of these three fields are required to obtain relevant timing
   information on the operation.  However, when some kind of Logging
   aggregation/summarization is used, it can be advantageous to keep the
   three fields: for instance, in the case of HAS, keeping the three
   fields permits computing an average delivery bitrate from a single
   Logging Record aggregating information on the delivery of multiple
   consecutive video chunks.

   Multiple header fields, in addition to the ones explicitly listed in
   the table could be reproduced in the Logging records.

   Note that uCDN may want to filter Logging data by user (and not by IP
   address) to provide more relevant information to the CSP.  In such
   case, a user may be identified as a combination of several pieces of
   information such as the client IP and User Agent or through the SID.

   The URI_full provides information on the Surrogate that provided the
   content.  This information can be relevant, for instance, for the
   Inter-Affiliates use case described in [I-D.ietf-cdni-use-cases].
   However, in some cases it may be considered as confidential and the
   dCDN may provide URI_part instead.

4.1.2.  Syntax of Generic CDNI Logging Fields

   Table 2 illustrates the definition of the information elements.  It
   provides examples using Apache log format strings [apache] when they
   exist.

   [Ed Note, this should be replaced with actual selected format for
   CDNI]




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   [Ed. note: specify for all Logging Fields the type (e.g., varchar,
   int, float, ...) and the maximum size (e.g., varchar(200))]

   +----------+-------------------+------------------------------------+
   | Name     | String            | Example                            |
   +----------+-------------------+------------------------------------+
   | Time     | %t                | [10/Oct/2000:13:55:36-0700]        |
   | Duration | %D                | -                                  |
   | Client-I | %a                | 203.0.113.45                       |
   | P        |                   |                                    |
   | Operatio | -                 | -                                  |
   | n        |                   |                                    |
   | URI_full | %U                | -                                  |
   | Protocol | %H                | HTTP/1.0                           |
   | Request  | %m                | GET                                |
   | method   |                   |                                    |
   | Status   | %>s               | 200                                |
   | Bytes    | %O                | 2326                               |
   | Sent     |                   |                                    |
   | Bytes    | %I                | 432                                |
   | received |                   |                                    |
   | Header   | \"%{Referrer}i\"  | "http://www.example.com/start.html |
   |          | \"%{User-agent}i\ | ""Mozilla/4.08 [en] (Win98; I      |
   |          | "                 |  ;Nav)"                            |
   +----------+-------------------+------------------------------------+

                   Table 2: Examples using Apache format

4.2.  Logging Fields for Content Delivery

   Beyond the Logging Fields described in previous section, this section
   defines additional Logging Fields that are specifically related to
   Content Delivery operations.  Note that the uCDN may not transfer the
   information provided in some of these fields to the CSP, depending on
   the CSP's interest in the information and on the information's
   confidentiality level.

4.2.1.  Semantics for Delivery CDNI Logging Fields

   The semantics of the generic CDNI Logging Fileds are specified in
   Table 3.










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   +-------------------+-----------------------------------------------+
   | Name              | Definition                                    |
   +-------------------+-----------------------------------------------+
   | uCDN-ID           | An element authenticating the operator of the |
   |                   | uCDN as the authority having delegated the    |
   |                   | request to the dCDN.                          |
   | Delivering-CDN-ID | An identifier (e.g., an aggregation of an IP  |
   |                   | address and a FQDN) of the Delivering CDN.    |
   |                   | The Delivering-CDN-ID might be considered as  |
   |                   | confidential by the dCDN.  In such case, the  |
   |                   | dCDN could either not provide this field to   |
   |                   | the uCDN or overwrite the Delivering-CDN-ID   |
   |                   | with its on identifier.                       |
   | Cache-bytes       | The number of body bytes served from caches.  |
   |                   | This quantity permits the computation of the  |
   |                   | byte hit ratio.                               |
   | Action            | The Action describes how a given request was  |
   |                   | treated locally: through which transport      |
   |                   | protocol, with or without content             |
   |                   | revalidation, with a cache hit or cache miss, |
   |                   | with fresh or stale content, and (if          |
   |                   | relevant) with which error.  Example with     |
   |                   | Squid format [squid]: "TCP_REFRESH_FAIL_HIT"  |
   |                   | means that an expired copy of an object       |
   |                   | requested through TCP was in the cache.       |
   |                   | Squid attempted to make an If-Modified-Since  |
   |                   | request, but it failed.  The old (stale)      |
   |                   | object was delivered to the client.           |
   +-------------------+-----------------------------------------------+

          Table 3: Semantics of the Delivery CDNI Logging Fields

   [Ed. note: Other information that could be logged include operations
   related to the authorization of the requests, URL rewriting rules
   enforced, the X-FORWARDED-FOR non standard HTTP header...]

4.2.2.  Syntax for Delivery CDNI Logging Fields

   [Ed Note: To be added]

4.3.  Logging Fields for Content Acquisition

   This section specifies Logging fields that are specific to Content
   Acquisition operations.







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4.3.1.  Semantics for Acquisition CDNI Logging Fields

   Table 4 specifies the semantics of the Acquisition specific CDNI
   Logging Fields.

   +--------------------+----------------------------------------------+
   | Name               | Definition                                   |
   +--------------------+----------------------------------------------+
   | dCDN identifier    | An element authenticating the operator of    |
   |                    | the dCDN as the authority requesting the     |
   |                    | content to the uCDN                          |
   | Caching_date       | Date at which the delivered content was      |
   |                    | stored in cache                              |
   | Validity_headers   | A copy of all headers related to content     |
   |                    | validity: no-cache, ETag, Vary,              |
   |                    | last-modified...                             |
   | Lookup_duration    | Duration of the DNS resolution for resolving |
   |                    | the FQDN of (uCDN's or CSP's) origin server. |
   | Delay_to_first_bit | Duration of the operations from the sending  |
   |                    | of the content acquisition request to the    |
   |                    | reception of the first bit of the requested  |
   |                    | content.                                     |
   | Delay_to_last_bit  | Duration of the operations from the sending  |
   |                    | of the content acquisition request to the    |
   |                    | reception of the last bit of the requested   |
   |                    | content.                                     |
   +--------------------+----------------------------------------------+

         Table 4: Semantics of the Acquisition CDNI Logging Fields

   These information elements may be used in Content Acquisition Logging
   provided by dCDN to uCDN and, potentially, in Content Acquisition
   Logging provided by uCDN to dCDN.

4.3.2.  Syntax for Acquisition CDNI Logging Fields

   [Ed Note: To be added]

4.4.  Logging Fields for Control

   [Ed. note: LOGS RELATED TO KEY EXCHANGES FOR INSTANCE, SECTION TO BE
   WRITTEN AFTER THE CONTROL INTERFACE IS MORE CLEARLY DEFINED]

4.5.  Logging Fields for Other Operations

   Logging can be used for debugging.  Therefore, all kinds of CDN
   operations might be logged, depending on the agreement between the
   dCDN and the uCDN.  In particular, operations related to Request



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   Routing and Metadata can be logged.


5.  CDNI Logging Records

   [Ed. note: we need to specify the encoding of the file, the
   separation character, etc...]

   This section defines a set of central events that a dCDN should
   register and publish through the Logging interface.

   We classify the logged events depending on the CDN operation to which
   they relate: Content Delivery, Content Acquisition, Content
   Invalidation/Purging, etc.

5.1.  Content Delivery

   Some CSPs pay a lot of attention to the protection of their content
   (e.g., premium video CSPs).  To fulfill the needs of these CSPs, a
   CDN shall log all the details of the content delivery authorizations.
   This means that a dCDN must be able to provide Logging detailing the
   content delivery/content acquisition authorizations and denials as
   well as information on why the request is authorized/denied.

   CSPs and CDN service providers pay a lot of attention to errors
   related to content delivery.  It is therefore of upmost importance
   that the dCDN provides detailed error information in the Logging
   data.  This information should typically be available even when
   Logging is aggregated.

   The content delivery events triggering the generation of a Logging
   Record include:

   o  Reception of a content request,

   The generated Logging Record typically embeds information about:

   o  Denial of delivery (error or unauthorized request, e.g., HTTP 401)
      for a request,

   o  Beginning of delivery (authorization) of a requested content,

   o  End of an authorized delivery (success),

   o  End of an authorized delivery (failure during the delivery, e.g.,
      HTTP 403).





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5.2.  Content Acquisition

5.2.1.  Logging Records Provided by dCDN to uCDN

   When the uCDN requires the dCDN to provide Logging for acquisition
   related events, the events triggering the generation of a Logging
   Record include:

   o  Emission of a content acquisition request (first try or retry) for
      a cache hit or a cache miss with content revalidation

   The generated Logging Record typically embeds information about:

   o  Reception of a reply indicating denial of delivery (error or
      unauthorized request) for a content acquisition request,

   o  End of an authorized acquisition (success),

   o  End of an authorized acquisition (failure)

   Note that a dCDN may acquire content only from the uCDN.  It this
   case, the uCDN can log the dCDN's content acquisition operations
   itself, and thus, the uCDN may not require the dCDN to log
   acquisition related events.  However, comparing the dCDN and uCDN
   logs is often useful for debugging and for security auditing.

5.2.2.  Logging Records Provided by uCDN to dCDN

   When the dCDN requires the uCDN to provide Logging for acquisition
   related events, the events triggering the generation of a Logging
   Record include:

   o  Reception of a content acquisition request for the considered
      Delivery Service for a cache hit or a cache miss with content
      revalidation

   The generated Logging Record typically embeds information about:

   o  Emission of a reply indicating denial of delivery (error or
      unauthorized request) for a content acquisition request,

   o  End of an authorized acquisition (success),

   o  End of an authorized acquisition (failure).







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5.3.  Content Invalidation and Purging

   When the uCDN requests a dCDN to log invalidation/purging events
   (e.g., for security), the events triggering the generation of a
   Logging Record include:

   o  Reception of a content invalidation/purging request

   The generated Logging Record typically embeds information about:

   o  Denial of the invalidation/purging request (error or unauthorized
      request, with details about the causes of the error),

   o  Beginning of invalidation/purging (authorization) for a given
      content purging request,

   o  End of an authorized invalidation/purging (success),

   o  End of an authorized invalidation/purging (failure).

5.4.  Logging Extensibility

   Future usages might introduce the need for additional Logging fields.
   In addition, some use-cases such as an Inter-Affiliate
   Interconnection [I-D.ietf-cdni-use-cases], might take advantage of
   extended Logging exchanges.  Therefore, it is important to permit
   CDNs to use additional Logging fields besides the standard ones, if
   they want.  For instance, an "Account-name" identifying the contract
   enforced by the dCDN for a given request could be provided in
   extended fields.

   The required Logging Records may depend on the considered services.
   For instance, static file delivery (e.g., pictures) typically does
   not include any delivery restrictions.  By contrast, video delivery
   typically implies strong content delivery restrictions, as explained
   in [I-D.ietf-cdni-use-cases], and Logging could include information
   about the enforcement of these restrictions.  Therefore, to ease the
   support of varied services as well as of future services, the Logging
   interface should support optional Logging Records.


6.  CDNI Logging File Format

   Interconnected CDNs may support various Logging formats.  However,
   they must support at least the default Logging File format described
   here.





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6.1.  Logging Files

   [Ed.  Note: How many files (one per type of Delivery Service (e.g.,
   HTTP, WMP) and per type of Event (e.g., Errors, Delivery,
   Acquisition,...?)and what would be inside...  These aspects needs to
   be detailed...]

6.2.  File Format

   The Logging file format should be independent from the selected
   transport protocol, to guarantee a flexible choice of transport
   protocols.  [Ed. note: for the real time Logging exchanges, this
   might be hard]

   All Logging Records in a Logging File must share the same format
   (same set of Logging Fields, in the same order, with the same
   semantics, separated by the same Separator Character), to ease the
   parsing of the Logging data by the CDN that receives the Logging
   File.  The CDN that provides the Logging data is responsible for
   guaranteeing the consistency of the Logging records' formats,
   typically via its log filtering and aggregation processes (see
   Section 2.2.3).

6.2.1.  Headers

   Logging files must include a header with the information described in
   Figure 5.
























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   +----------------+-------------------+------------------------------+
   | Field          | Description       | Examples                     |
   +----------------+-------------------+------------------------------+
   | Format         | Identification of | standard_cdni_errors_http_v1 |
   |                | CDNI Log format.  |                              |
   | Fields         | A description of  |                              |
   |                | the record format |                              |
   |                | (list of fields). |                              |
   | Log-ID         | Identifier        | abcdef1234                   |
   |                | for the CDNI Log  |                              |
   |                | file (facilitates |                              |
   |                | detection of      |                              |
   |                | duplicate Logs    |                              |
   |                | and tracking in   |                              |
   |                | case of           |                              |
   |                | aggregation).     |                              |
   | Log-Timestamp  | Time, in          | [20/Feb/2012:00:29.510+0200] |
   |                | milliseconds, the |                              |
   |                | CDNI Log was      |                              |
   |                | generated.        |                              |
   | Log-Origin     | Identifier of the | cdn1.cdni.example.com        |
   |                | authority (e.g.,  |                              |
   |                | dCDN or uCDN)     |                              |
   |                | providing the Log-|                              |
   |                | -ging             |                              |
   +----------------+-------------------+------------------------------+


                         Figure 5: Logging Headers

   All time-related Logging Fields and data in the Logging File headers/
   footers must provide a time zone and be at least at millisecond (ms)
   accuracy.  The accuracy must be consistent to permit the computation
   of KPIs involving operations realized on several CDNs.

   [Ed. note: would it make sense to add a kind of "example Logging
   Record" in the Logging file and associated semantic (e.g. in a
   structure data format) ?]

6.2.2.  Body (Logging Records) Format

   [Ed. note: the W3C extended log format is a good base candidate to
   look at.]

   [Ed. note: Records used for real time information and non-real time
   information could use different formats.  In this version, we do not
   yet tackle the problem of real time logging exchanges]




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6.2.3.  Footer Format

   Logging files must include a footer with the information described in
   Figure 6.


   +---------+----------------------------------------------+----------+
   | Field   | Description                                  | Examples |
   +---------+----------------------------------------------+----------+
   | Log     | Digest of the complete Log (facilitates      |          |
   | Digest  | detection of Log corruption)                 |          |
   +---------+----------------------------------------------+----------+


                         Figure 6: Logging footers

   This digest field permits the detection of corrupted Logging files.
   This can be useful, for instance, if a problem occurs on the
   filesystem of the dCDN Logging system and leads to a truncation of a
   logging file.  Additional mechanisms to avoid corrupted Logging files
   are expected to be provided by the Logging transport protocol, cf.
   Section 7.


7.  CDNI Logging File Transport Protocol

   As presented in [RFC6707], several protocols already exist that could
   potentially be used to exchange CDNI Logging between interconnected
   CDNs.

   The offline exchange of non real-time Logging could rely on several
   protocols.  In particular, the dCDN could publish the Logging on a
   server where the uCDN would retrieve them using a secure protocol
   (yet to be identified).

   [Ed. note: Propose protocol, e.g.  SSH File Transfer Protocol (SFTP)
   [I-D.ietf-secsh-filexfer]. and add call flow]

   [Ed note: include options for lossless compression]


8.  Logging Control

   The CDNI Control interface is responsible for correctly configuring
   the Logging interface between interconnected CDNs, for every Delivery
   Service and according to the Logging configuration agreed during
   business negotiations.




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   This section will identify the parameters that the CDNI Control
   interface should manage on uCDN and dCDN for activating, updating, or
   removing a CDNI Logging configuration for a given Delivery Service.

   [Ed.  Note: uCDN shall be able to select the type of events that a
   dCDN should include in the Logging that the latter provides to the
   uCDN.  This will be discussed during business negotiations and the
   Control must enforce the agreed configuration.  The use of multiple
   levels of Logging granularity such as Syslog's "severity levels"
   (Emergency, Alert, Critical, ..., Debug) [RFC5424] may help in
   providing the most relevant amount of information depending on the
   intended Logging usage, as specified during the Logging format
   negotiation.]

   [Ed. note: the specification all Logging Fields' maximum size (e.g.,
   varchar(200)) might be constrained in some CDNs so need to exchange
   that information during the configuration]


9.  Open Issues

   The main remaining tasks on this ID are the following:

   o  Detail the Logging Fields' syntax

   o  Recommend a Logging File Transport Protocol and detail the call-
      flows

   o  Detail mechanisms for Real-Time Logging

   [Ed.  Note: The format for Time is still to be agreed on.  RFC 5322
   (Section 3.3) format could be used or ISO 8601 formatted date and
   time in UTC (same format as proposed in
   [draft-caulfield-cdni-metadata-core-00]).  Also see RFC5424 Section 
   6.2.3.]

   [Ed.  Note:When to log the end of a session when the End-User pauses
   a video display?]

   [Ed. note: (comment from Kevin) how are errors handled ?  If the
   client gets handed a bunch of 403s and 404s, but still gets the
   content eventually, without triggering an event, are those still
   logged?  For Bytes-Sent, if there were aborted requests, do those get
   counted as well?  Not all client behavior can be correlated with the
   simplified log]






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10.  IANA Considerations

   This memo includes no request to IANA.


11.  Security Considerations

11.1.  Privacy

   CDNs have the opportunity to collect detailed information about the
   downloads performed by End-Users.  The provision of this information
   to another CDN introduces End-Users privacy protection concerns.

11.2.  Non Repudiation

   Logging provides the raw material for charging.  It permits the dCDN
   to bill the uCDN for the content deliveries that the dCDN makes on
   behalf of the uCDN.  It also permits the uCDN to bill the CSP for the
   content Delivery Service.  Therefore, non-repudiation of Logging data
   is essential.


12.  Acknowledgments

   The authors would like to thank Sebastien Cubaud, Anne Marrec,
   Yannick Le Louedec, and Christian Jacquenet for detailed feedback on
   early versions of this document and for their input on existing Log
   formats.

   The authors would like also to thank Fabio Costa, Yvan Massot, Renaud
   Edel, and Joel Favier for their input and comments.

   Finally, they thank the contributors of the EU FP7 OCEAN project for
   valuable inputs.


13.  References

13.1.  Normative References

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

   [RFC5424]  Gerhards, R., "The Syslog Protocol", RFC 5424, March 2009.







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13.2.  Informative References

   [CLF]      A. Luotonen, "The Common Log-file Format, W3C (work in
              progress)", 1995, <http://www.w3.org/pub/WWW/Daemon/User/
              Config/Logging.html>.

   [ELF]      Phillip M. Hallam-Baker and Brian Behlendorf, "Extended
              Log File Format, W3C (work in progress), WD-logfile-
              960323", <http://www.w3.org/TR/WD-logfile.html>.

   [I-D.bertrand-cdni-experiments]
              Faucheur, F. and L. Peterson, "Content Distribution
              Network Interconnection (CDNI) Experiments",
              draft-bertrand-cdni-experiments-02 (work in progress),
              February 2012.

   [I-D.brandenburg-cdni-has]
              Brandenburg, R., Deventer, O., Faucheur, F., and K. Leung,
              "Models for adaptive-streaming-aware CDN Interconnection",
              draft-brandenburg-cdni-has-03 (work in progress),
              July 2012.

   [I-D.ietf-cdni-framework]
              Peterson, L. and B. Davie, "Framework for CDN
              Interconnection", draft-ietf-cdni-framework-01 (work in
              progress), July 2012.

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

   [I-D.ietf-cdni-use-cases]
              Bertrand, G., Emile, S., Burbridge, T., Eardley, P., Ma,
              K., and G. Watson, "Use Cases for Content Delivery Network
              Interconnection", draft-ietf-cdni-use-cases-10 (work in
              progress), August 2012.

   [I-D.ietf-secsh-filexfer]
              Galbraith, J. and O. Saarenmaa, "SSH File Transfer
              Protocol", draft-ietf-secsh-filexfer-13 (work in
              progress), July 2006.

   [RFC6707]  Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
              Distribution Network Interconnection (CDNI) Problem
              Statement", RFC 6707, September 2012.




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   [apache]   "Apache 2.2 log files documentation", Feb. 2012,
              <http://httpd.apache.org/docs/current/logs.html>.

   [squid]    "Squid Log-Format documentation", Feb. 2012,
              <http://wiki.squid-cache.org/SquidFaq/SquidLogs>.


Appendix A.  Examples Log Format

   This section provides example of log formats implemented in existing
   CDNs, web servers, and caching proxies.

   Web servers (e.g., Apache) maintain at least one log file for logging
   accesses to content (the Access Log).  They can typically be
   configured to log errors in a separate log file (the Error Log).  The
   log formats can be specified in the server's configuration files.
   However, webmasters often use standard log formats to ease the log
   processing with available log analysis tools.

A.1.  W3C Common Log File (CLF) Format

   The Common Log File (CLF) format defined by the World Wide Web
   Consortium (W3C) working group is compatible with many log analysis
   tools and is supported by the main web servers (e.g., Apache) Access
   Logs.

   According to [CLF], the common log-file format is as follows:
   remotehost rfc931 authuser [date] "request" status bytes.

   Example (from [apache]): 127.0.0.1 - frank [10/Oct/2000:13:55:36
   -0700] "GET /apache_pb.gif HTTP/1.0" 200 2326

   The fields are defined as follows [CLF]:

   +------------+------------------------------------------------------+
   | Element    | Definition                                           |
   +------------+------------------------------------------------------+
   | remotehost | Remote hostname (or IP number if DNS hostname is not |
   |            | available, or if DNSLookup is Off.                   |
   | rfc931     | The remote logname of the user.                      |
   | authuser   | The username that the user employed to authenticate  |
   |            | himself.                                             |
   | [date]     | Date and time of the request.                        |
   | "request"  | An exact copy of the request line that came from the |
   |            | client.                                              |
   | status     | The status code of the HTTP reply returned to the    |
   |            | client.                                              |




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   | bytes      | The content-length of the document transferred.      |
   +------------+------------------------------------------------------+

                Table 5: Information elements in CLF format

A.2.  W3C Extended Log File (ELF) Format

   The Extended Log File (ELF) format defined by W3C extends the CLF
   with new fields.  This format is supported by Microsoft IIS 4.0 and
   5.0.

   The supported fields are listed below [ELF].

    +------------+---------------------------------------------------+
    | Element    | Definition                                        |
    +------------+---------------------------------------------------+
    | date       | Date at which transaction completed               |
    | time       | Time at which transaction completed               |
    | time-taken | Time taken for transaction to complete in seconds |
    | bytes      | bytes transferred                                 |
    | cached     | Records whether a cache hit occurred              |
    | ip         | IP address and port                               |
    | dns        | DNS name                                          |
    | status     | Status code                                       |
    | comment    | Comment returned with status code                 |
    | method     | Method                                            |
    | uri        | URI                                               |
    | uri-stem   | Stem portion alone of URI (omitting query)        |
    | uri-query  | Query portion alone of URI                        |
    +------------+---------------------------------------------------+

                Table 6: Information elements in ELF format

   Some fields start with a prefix (e.g., "c-", "s-"), which explains
   which host (client/server/proxy) the field refers to.

   o  Prefix Description

   o  c- Client

   o  s- Server

   o  r- Remote

   o  cs- Client to Server.

   o  sc- Server to Client.




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   o  sr- Server to Remote Server (used by proxies)

   o  rs- Remote Server to Server (used by proxies)

   Example: date time s-ip cs-method cs-uri-stem cs-uri-query s-port cs-
   username c-ip cs(User-Agent) sc-status sc-substatus sc-win32-status
   time-taken

   2011-11-23 15:22:01 x.x.x.x GET /file 80 y.y.y.y Mozilla/
   5.0+(Windows;+U;+Windows+NT+6.1;+en-US;+rv:1.9.1.6)+Gecko/
   20091201+Firefox/3.5.6+GTB6 200 0 0 2137

A.3.  National Center for Supercomputing Applications (NCSA) Common Log
      Format

   This format for Access Logs offers the following fields:

   o  host rfc931 date:time "request" statuscode bytes

   o  x.x.x.x userfoo [10/Jan/2010:21:15:05 +0500] "GET /index.html
      HTTP/1.0" 200 1043

A.4.  NCSA Combined Log Format

   The NCSA Combined log format is an extension of the NCSA Common log
   format with three (optional) additional fields: the referral field,
   the user_agent field, and the cookie field.

   o  host rfc931 username date:time request statuscode bytes referrer
      user_agent cookie

   o  Example: x.x.x.x - userfoo [21/Jan/2012:12:13:56 +0500] "GET
      /index.html HTTP/1.0" 200 1043 "http://www.example.com/" "Mozilla/
      4.05 [en] (WinNT; I)" "USERID=CustomerA;IMPID=01234"

A.5.  NCSA Separate Log Format

   The NCSA Separate log format refers to a log format in which the
   information gathered is separated into three separate files.  This
   way, every entry in the Access Log (in the NCSA Common log format) is
   complemented with an entry in a Referral log and another one in an
   Agent log.  These three records can be correlated easily thanks to
   the date:time value.  The format of the Referral log is as follows:

   o  date:time referrer

   o  Example: [21/Jan/2012:12:13:56 +0500]
      "http://www.example.com/index.html"



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   The format of the Agent log is as follows:

   o  date:time agent

   o  [21/Jan/2012:12:13:56 +0500] "Microsoft Internet Explorer - 5.0"

A.6.  Squid 2.0 Native Log Format for Access Logs

   Squid [squid] is a popular piece of open-source software for
   transforming a Linux host into a caching proxy.  Variations of Squid
   log format are supported by some CDNs.

   Squid common access log format is as follow: time elapsed remotehost
   code/status bytes method URL rfc931 peerstatus/peerhost type.

   Squid also supports a more detailed native access log format:
   Timestamp Elapsed Client Action/Code Size Method URI Ident Hierarchy/
   From Content

   According to Squid 2.0 documentation [squid], these fields are
   defined as follows:

   +-----------+-------------------------------------------------------+
   | Element   | Definition                                            |
   +-----------+-------------------------------------------------------+
   | time      | Unix timestamp as UTC seconds with a millisecond      |
   |           | resolution.                                           |
   | duration  | The elapsed time in milliseconds the transaction      |
   |           | busied the cache.                                     |
   | client    | The client IP address.                                |
   | address   |                                                       |
   | bytes     | The size is the amount of data delivered to the       |
   |           | client, including headers.                            |
   | request   | The request method to obtain an object.               |
   | method    |                                                       |
   | URL       | The requested URL.                                    |
   | rfc931    | may contain the ident lookups for the requesting      |
   |           | client (turned off by default)                        |
   | hierarchy | The hierarchy information provides information on how |
   | code      | the request was handled (forwarding it to another     |
   |           | cache, or requesting the content to the Origin        |
   |           | Server).                                              |
   | type      | The content type of the object as seen in the HTTP    |
   |           | reply header.                                         |
   +-----------+-------------------------------------------------------+

               Table 7: Information elements in Squid format




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   Squid also uses a "store log", which covers the objects currently
   kept on disk or removed ones, for debugging purposes typically.


Appendix B.  Requirements

B.1.  Additional Requirements

   Section 7 of [I-D.ietf-cdni-requirements], already specifies a set of
   requirements for Logging (LOG-1 to LOG-16).  Some security
   requirements also affect Logging (e.g., SEC-4).

   This section is a placeholder for requirements identified in the work
   on logging, before they are proposed to the requirements draft
   authors.

   Logging data is sensitive as it provides the raw material for
   producing bills etc.  Therefore, the protocol delivering the Logging
   data must be reliable to avoid information loss.  In addition, the
   protocol must scale to support the transport of large amounts of
   Logging data.

   CDNs need to trust Logging information, thus, they want to know:

   o  who issued the Logging (authentication), and

   o  if the Logging has been modified by a third party (integrity).

   Logging also contains confidential data, and therefore, it should be
   protected from eavesdropping.

   All these needs translate into security requirements on both the
   Logging data format and on the Logging protocol.

   Finally, this protocol must comply with the requirements identified
   in [I-D.ietf-cdni-requirements].

   [Ed. note: cf. requirements draft: "SEC-4 [MED] The CDNI solution
   should be able to ensure that the Downstream CDN cannot spoof a
   transaction log attempting to appear as if it corresponds to a
   request redirected by a given Upstream CDN when that request has not
   been redirected by this Upstream CDN.  This ensures non-repudiation
   by the Upstream CDN of transaction logs generated by the Downstream
   CDN for deliveries performed by the Downstream CDN on behalf of the
   Upstream CDN."]






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B.2.  Compliancy with Requirements draft

   This section checks that all the identified requirements in the
   Requirements draft are fulfilled by this document.

   [Ed. node: to be written later]


Appendix C.  CDNI WG's position on candidate protocols for Logging
             Transport

   This section will be expanded later with the position of the WG
   considering the alternative candidate protocols for Logging in CDNI.

   [Ed.  Note: in a later version, this memo will include an analysis of
   candidate protocols, based upon a set of (basic) requirements, such
   as reliable transport mode, preservation of the integrity of the
   information conveyed by the protocol, etc.]

C.1.  CDNI WG's position on Syslog

   [Ed. node: to be written later]

   [Ed. note: add a few sentences to clarify why not directly use
   syslog...  Operational reasons... ]

C.2.  CDNI WG's position on SNMP

   As explained in [RFC6707], "SNMP traps pose scalability concerns and
   SNMP does not support guaranteed delivery of Traps and therefore
   could result in log records being lost and the consequent CoDRs and
   billing records for that content delivery not being produced as well
   as that content delivery being invisible to any analytics platforms."


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






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

   Email: emile.stephan@orange.com


   Roy Peterkofsky
   Skytide, Inc.
   One Kaiser Plaza, Suite 785
   Oakland  CA 94612
   USA

   Phone: +01 510 250 4284
   Email: roy@skytide.com


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

   Phone: +33 4 97 23 26 19
   Email: flefauch@cisco.com


   Pawel Grochocki
   Orange Polska
   ul. Obrzezna 7
   Warsaw  02-691
   Poland

   Email: pawel.grochocki@orange.com















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