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RFC 7937

Proposed STD
Pages: 63
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Content Distribution Network Interconnection (CDNI) Logging Interface

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Internet Engineering Task Force (IETF)               F. Le Faucheur, Ed.
Request for Comments: 7937
Category: Standards Track                               G. Bertrand, Ed.
ISSN: 2070-1721
                                                         I. Oprescu, Ed.

                                                          R. Peterkofsky
                                                             Google Inc.
                                                             August 2016


 Content Distribution Network Interconnection (CDNI) Logging Interface

Abstract

   This memo specifies the Logging interface between a downstream
   Content Distribution Network (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 CDNI Logging File format and the actual protocol for
   exchange of CDNI Logging Files.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7937.

[Page 2] 
Copyright Notice

   Copyright (c) 2016 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   5
   2.  CDNI Logging Reference Model  . . . . . . . . . . . . . . . .   5
     2.1.  CDNI Logging Interactions . . . . . . . . . . . . . . . .   5
     2.2.  Overall Logging Chain . . . . . . . . . . . . . . . . . .   9
       2.2.1.  Logging Generation and During-Generation Aggregation   10
       2.2.2.  Logging Collection  . . . . . . . . . . . . . . . . .  11
       2.2.3.  Logging Filtering . . . . . . . . . . . . . . . . . .  11
       2.2.4.  Logging Rectification and Post-Generation Aggregation  12
       2.2.5.  Log-Consuming Applications  . . . . . . . . . . . . .  13
         2.2.5.1.  Maintenance and Debugging . . . . . . . . . . . .  13
         2.2.5.2.  Accounting  . . . . . . . . . . . . . . . . . . .  14
         2.2.5.3.  Analytics and Reporting . . . . . . . . . . . . .  14
         2.2.5.4.  Content Protection  . . . . . . . . . . . . . . .  14
         2.2.5.5.  Notions Common to Multiple Log-Consuming
                   Applications  . . . . . . . . . . . . . . . . . .  15
   3.  CDNI Logging File . . . . . . . . . . . . . . . . . . . . . .  17
     3.1.  Rules . . . . . . . . . . . . . . . . . . . . . . . . . .  17
     3.2.  CDNI Logging File Structure . . . . . . . . . . . . . . .  18
     3.3.  CDNI Logging Directives . . . . . . . . . . . . . . . . .  21
     3.4.  CDNI Logging Records  . . . . . . . . . . . . . . . . . .  26
       3.4.1.  HTTP Request Logging Record . . . . . . . . . . . . .  27
     3.5.  CDNI Logging File Extension . . . . . . . . . . . . . . .  38
     3.6.  CDNI Logging File Examples  . . . . . . . . . . . . . . .  38
     3.7.  Cascaded CDNI Logging Files Example . . . . . . . . . . .  42

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   4.  Protocol for Exchange of CDNI Logging File after Full
       Collection  . . . . . . . . . . . . . . . . . . . . . . . . .  44
     4.1.  CDNI Logging Feed . . . . . . . . . . . . . . . . . . . .  45
       4.1.1.  Atom Formatting . . . . . . . . . . . . . . . . . . .  45
       4.1.2.  Updates to Log Files and the Feed . . . . . . . . . .  46
       4.1.3.  Redundant Feeds . . . . . . . . . . . . . . . . . . .  47
       4.1.4.  Example CDNI Logging Feed . . . . . . . . . . . . . .  47
     4.2.  CDNI Logging File Pull  . . . . . . . . . . . . . . . . .  49
   5.  Protocol for Exchange of CDNI Logging File During Collection   50
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  51
     6.1.  CDNI Logging Directive Names Registry . . . . . . . . . .  51
     6.2.  CDNI Logging File version Registry  . . . . . . . . . . .  51
     6.3.  CDNI Logging record-types Registry  . . . . . . . . . . .  52
     6.4.  CDNI Logging Field Names Registry . . . . . . . . . . . .  53
     6.5.  CDNI Logging Payload Type . . . . . . . . . . . . . . . .  55
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  55
     7.1.  Authentication, Authorization, Confidentiality, and
           Integrity Protection  . . . . . . . . . . . . . . . . . .  55
     7.2.  Denial of Service . . . . . . . . . . . . . . . . . . . .  56
     7.3.  Privacy . . . . . . . . . . . . . . . . . . . . . . . . .  57
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  58
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  58
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  61
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  63
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  63

1.  Introduction

   This memo specifies the CDNI 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 CDNI
   Logging File format and the actual protocol for exchange of CDNI
   Logging Files.

   The reader should be familiar with the following documents:

   o  CDNI problem statement [RFC6707] and framework [RFC7336], which
      identify a Logging interface,

   o  Section 8 of [RFC7337], which specifies a set of requirements for
      Logging,

   o  [RFC6770] outlines real world use cases for interconnecting CDNs.
      These use cases require the exchange of Logging information
      between the dCDN and the uCDN.

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   As stated in [RFC6707], "the CDNI Logging interface enables details
   of content distribution and delivery activities to be exchanged
   between interconnected CDNs."

   The present document describes:

   o  The CDNI Logging reference model (Section 2)

   o  The CDNI Logging File format (Section 3)

   o  The CDNI Logging File Exchange protocol (Section 4)

1.1.  Terminology

   In this document, the first letter of each CDNI-specific term is
   capitalized.  We adopt the terminology described in [RFC6707] and
   [RFC7336], and extend it with the additional terms defined below.

   Intra-CDN Logging information: Logging information generated and
   collected within a CDN.  The format of the Intra-CDN Logging
   information may be different from the format of the CDNI Logging
   information.

   CDNI Logging information: Logging information exchanged across CDNs
   using the CDNI Logging interface.

   Logging information: Logging information generated and collected
   within a CDN or obtained from another CDN using the CDNI Logging
   interface.

   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
   Uniform Resource Identifier (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.

   CDNI Logging File: A file containing CDNI Logging Records, as well as
   additional information facilitating the processing of the CDNI
   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 Content Service Provider (CSP) in deferred time.  Such
   information typically includes aggregated data that can cover a large

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   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 or displaying content
   delivery information in a timely fashion with respect to the
   corresponding deliveries.  Monitoring typically includes 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.

1.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in RFC
   2119 [RFC2119].

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  customization by the uCDN of the CDNI Logging information to be
      provided by the dCDN to the uCDN (e.g., control of which CDNI
      Logging fields are to be communicated to the uCDN for a given task
      performed by the dCDN or control of which types of events are to
      be logged).  The dCDN takes into account this CDNI Logging
      customization information to determine what Logging information to
      provide to the uCDN, but it may, or may not, take into account
      this CDNI Logging customization information to influence what CDN
      Logging information is to be generated and collected within the
      dCDN (e.g., even if the uCDN requests a restricted subset of the
      Logging information, the dCDN may elect to generate a broader set
      of Logging information).  The mechanism to support the
      customization by the uCDN of CDNI Logging information is outside
      the scope of this document and is left for further study.  Until
      such a mechanism is available, the uCDN and dCDN are expected to
      agree off-line on what exact set of CDNI Logging information is to
      be provided by the dCDN to the uCDN, and to rely on management-
      plane actions to configure the CDNI Logging functions in the dCDN
      to generate this information set and in the uCDN to expect this
      information set.

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   o  generation and collection by the dCDN of the intra-CDN 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 and is in the scope of the present
      document.  For example, the uCDN may use this Logging information
      to charge the CSP, to perform analytics and monitoring for
      operational reasons, to provide analytics and monitoring views on
      its content delivery to the CSP, or to perform troubleshooting.
      This document exclusively specifies non-real-time exchange of
      Logging information.  Closer to real-time exchange of Logging
      information (say sub-minute or sub-second) is outside the scope of
      the present document and is left for further study.  This document
      exclusively specifies exchange of Logging information related to
      content delivery.  Exchange of Logging information related to
      operational events (e.g., dCDN request routing function
      unavailable and content acquisition failure by dCDN) for audit or
      operational reactive adjustments by uCDN is outside the scope of
      the present document and is left for further study.

   o  customization by the dCDN of the CDNI Logging information to be
      provided by the uCDN on behalf of the dCDN.  The mechanism to
      support the customization by the dCDN of CDNI Logging information
      is outside the scope of this document and is left for further
      study.

   o  generation and collection by the uCDN of Intra-CDN 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.  For example, the dCDN
      might potentially benefit from this information for security
      auditing or content acquisition troubleshooting.  This is outside
      the scope of this document and is left for further study.

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   Figure 1 provides an example of CDNI Logging interactions (focusing
   only on the interactions that are in the scope of this document) in a
   particular scenario where four CDNs are involved in the delivery of
   content from a given CSP: the uCDN has a CDNI interconnection with
   dCDN-1 and dCDN-2.  In turn, dCDN-2 has a CDNI interconnection with
   dCDN-3, where dCDN-2 is acting as an upstream CDN relative to dCDN-3.
   In this example, uCDN, dCDN-1, dCDN-2, and dCDN-3 all participate in
   the delivery of 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, the uCDN
   uses the Logging information:

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

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

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

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

   ===> CDNI Logging interface
   ***> outside the scope of CDNI

        Figure 1: Interactions in the CDNI Logging Reference Model

   A downstream CDN relative to uCDN (e.g., dCDN-2) integrates the
   relevant Logging information obtained from its own downstream CDNs
   (i.e., dCDN-3) in the Logging information 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.  Such
   aggregation is further discussed in Section 3.7.

   Note that the format of Logging information 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
   information before it provides this information to the other CDN over
   the CDNI Logging interface.  Similarly, a CDN might reformat the
   Logging information that it receives over the CDNI Logging interface
   before injecting it into its log-consuming applications or before
   providing some of this Logging information to the CSP.  Such
   reformatting operations introduce latency in the logging distribution
   chain and introduce a processing burden.  Therefore, there are
   benefits in specifying CDNI Logging formats that are suitable for use
   inside CDNs and also are close to the intra-CDN Logging formats
   commonly used in CDNs today.

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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 2 illustrates the overall logging chain
   within the dCDN, across CDNs using the CDNI Logging interface, and
   within the uCDN.  Note that the logging chain illustrated in the
   figure is obviously only an example and varies depending on the
   specific environments.  For example, there may be more or fewer
   instantiations of each entity (e.g., there may be 4 log-consuming
   applications in a given CDN).  As another example, there may be one
   instance of a Rectification process per log-consuming application
   instead of a shared one.

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

            Figure 2: CDNI Logging in the Overall Logging Chain

   The following subsections describe each of the processes potentially
   involved in the logging chain of Figure 2.

2.2.1.  Logging Generation and During-Generation Aggregation

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

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

   [RFC6983] 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 [RFC6983], the Logging information for per-chunk delivery may
   include some information (a Content Collection IDentifier and a
   Session IDentifier) 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 aggregate per-session
   logs for HAS delivery are for further study and are outside the scope
   of this document.

2.2.2.  Logging Collection

   This is the process that continuously collects Logging information
   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 2 where we see that the Collection process of the uCDN
   collects Logging information from log-generating entities within the
   uCDN as well as Logging information coming from the dCDNs through the
   CDNI Logging interface.

2.2.3.  Logging Filtering

   A CDN may be required to only present different subsets of the whole
   Logging information collected to various log-consuming applications.
   This is achieved by the Filtering process.

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   In particular, the Filtering process can also filter the right subset
   of Logging 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 out 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
   subset of Logging information that relates 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 [RFC6770], the interconnected CDNs do
   not want to disclose details on their internal topology.  The
   filtering process can then also filter confidential data on the
   dCDNs' topology (number of servers, location, etc.).  In particular,
   information about the requests served by each Surrogate may be
   confidential.  Therefore, the Logging information needs to be
   protected so that data such as the Surrogates' hostnames are 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 information 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 information of this period will be available only
   after the end of the session, which delays the Logging information
   generation.  A simple approach is to provide the complete Logging
   Record for a session in the Logging Period of the session end.

   A Logging rectification/update mechanism could be useful to reach a
   good trade-off between the Logging information generation delay and
   the Logging information accuracy.

   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.

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   In the case where aggregate logs have been generated directly by the
   log-generating entities, 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 [RFC6983], this
   document does not define the exchange of such aggregate logs on the
   CDNI Logging interface.  We note that this is for further study and
   is outside the scope of this document.

2.2.5.  Log-Consuming Applications

2.2.5.1.  Maintenance and Debugging

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

   To detect faults, Logging information needs to report the success and
   failure of CDN-delivery operations.  The uCDN can summarize such
   information into KPIs.  For instance, Logging information needs to
   allow the computation of the number of times, during a given time
   period, that content delivery related to a specific service succeeds
   or fails.

   Logging information enables the CDN providers to identify and
   troubleshoot performance degradations.  In particular, Logging
   information enables tracking 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.

   Some of these maintenance and debugging applications only require
   aggregate Logging information highly compatible with the use of
   anonymization of IP addresses (as supported by the present document
   and specified in the definition of the c-groupid field in
   Section 3.4.1).  However, in some situations, it may be useful, where
   compatible with privacy protection, to access some CDNI Logging
   Records containing full non-anonymized IP addresses.  This is allowed
   in the definition of the c-groupid (in Section 3.4.1), with very
   significant privacy protection limitations that are discussed in the
   definition of the c-groupid field.  For example, this may be useful
   for detailed fault tracking of a particular end-user content delivery
   issue.  Where there is a hard requirement by uCDN or CSP to associate
   a given end user to individual CDNI Logging Records (e.g., to allow a
   posteriori analysis of individual delivery, for example, in

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   situations of performance-based penalties), instead of using
   aggregates containing a single client as discussed in the c-groupid
   field definition, an alternate approach is to ensure that a client
   identifier is embedded in the request fields that can be logged in a
   CDNI Logging Record (for example, by including the client identifier
   in the URI query string or in an HTTP Header).  That latter approach
   offers two significant benefits: first, the aggregate inside the
   c-groupid can contain more than one client, thereby ensuring stronger
   privacy protection; second, it allows a reliable identification of
   the client while IP address does not in many situations (e.g., behind
   NAT, where dynamic IP addresses are used and reused, etc.).  However,
   care SHOULD be taken so that the client identifiers exposed in other
   fields of the CDNI Records cannot themselves be linked back to actual
   users.

2.2.5.2.  Accounting

   Logging information is essential for accounting, to permit inter-CDN
   billing and CSP billing by uCDNs.  For instance, Logging information
   provided by dCDNs enables the uCDN to compute the total amount of
   traffic delivered by every dCDN for a particular Content Provider, 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.

2.2.5.3.  Analytics and Reporting

   The goals of analytics include gathering any relevant information in
   order to be able to develop statistics on content download, analyze
   user behavior, and monitor the performance and quality of content
   delivery.  For instance, Logging information 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.  Content Protection

   The goal of content protection is to prevent and monitor unauthorized
   access, misuse, modification, and denial of access to content.  A set
   of information is logged in a CDN 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.

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2.2.5.5.  Notions Common to Multiple Log-Consuming Applications

2.2.5.5.1.  Logging Information Views

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

   For example, an analytics tool run by the uCDN can provide one view
   to a 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.

2.2.5.5.2.  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 the situation, these KPIs may be
   computed by the uCDN or by the dCDN.  But it is usually the uCDN that
   computes KPIs, because the 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)

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

   o  Top 10 most popularly requested contents (during a given day/week/
      month)

   o  Terminal type (mobile, PC, Set-Top Box (STB), if this information
      can be acquired from the browser type inferred from the User Agent
      string, for example)

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

   The KPIs used depend strongly on the considered log-consuming
   application -- the CDN operator may be interested in different
   metrics than the CSP.  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
   essentially if they are provided in a timely manner.  By contrast,
   some other KPIs, such as those averaged over a long period of time,
   can be provided in non-real-time.


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