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Internet Engineering Task Force                         G. Bertrand, Ed.
Internet-Draft                                                E. Stephan
Intended status: Informational                   France Telecom - Orange
Expires: August 16, 2012                               February 13, 2012


                         CDNI Logging Interface
                     draft-bertrand-cdni-logging-00

Abstract

   This memo specifies the Logging interface between a downstream CDN
   (dCDN) and an upstream CDN (uCDN).  It introduces a framework, an
   architecture design and a set of new requirements.  Then it drafts an
   information model.

Status of this Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on August 16, 2012.

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   This document may contain material from IETF Documents or IETF
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   material may not have granted the IETF Trust the right to allow
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   than English.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Abbreviations  . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Logging Framework  . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Architecture . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Additional Requirements  . . . . . . . . . . . . . . . . . . .  9
   5.  Rationale for Logging Interface  . . . . . . . . . . . . . . .  9
     5.1.  Usages of CDNI Logging Information By uCDN . . . . . . . .  9
       5.1.1.  Maintenance/Debugging  . . . . . . . . . . . . . . . .  9
       5.1.2.  Accounting . . . . . . . . . . . . . . . . . . . . . . 10
       5.1.3.  End-User Experience Management . . . . . . . . . . . . 10
       5.1.4.  Security . . . . . . . . . . . . . . . . . . . . . . . 10
     5.2.  Logging Information Views  . . . . . . . . . . . . . . . . 11
     5.3.  Information Extracted From Logging Data  . . . . . . . . . 11
   6.  Log Information Elements . . . . . . . . . . . . . . . . . . . 12
     6.1.  Core Information Elements  . . . . . . . . . . . . . . . . 13
     6.2.  Information Elements for Content Delivery  . . . . . . . . 14
     6.3.  Information Elements for Content Acquisition . . . . . . . 15
     6.4.  Log Extensibility  . . . . . . . . . . . . . . . . . . . . 15
   7.  Core Logging Records . . . . . . . . . . . . . . . . . . . . . 15
     7.1.  Content Delivery . . . . . . . . . . . . . . . . . . . . . 15
     7.2.  Content Acquisition  . . . . . . . . . . . . . . . . . . . 16
     7.3.  Content Purging  . . . . . . . . . . . . . . . . . . . . . 16
     7.4.  Extended CoDRs . . . . . . . . . . . . . . . . . . . . . . 17
   8.  Logging Process  . . . . . . . . . . . . . . . . . . . . . . . 17
     8.1.  Logging Aggregation  . . . . . . . . . . . . . . . . . . . 17
       8.1.1.  Logging and Fragmented Objects . . . . . . . . . . . . 18
     8.2.  Logging Protection . . . . . . . . . . . . . . . . . . . . 18
       8.2.1.  Logging Signing  . . . . . . . . . . . . . . . . . . . 18
     8.3.  Logging Filtering  . . . . . . . . . . . . . . . . . . . . 18
     8.4.  Logging Update and Rectification . . . . . . . . . . . . . 19
   9.  Protocols for Logging  . . . . . . . . . . . . . . . . . . . . 19
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 20



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   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 20
     11.1. Privacy  . . . . . . . . . . . . . . . . . . . . . . . . . 20
     11.2. Non Repudiation  . . . . . . . . . . . . . . . . . . . . . 20
   12. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 20
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 21
     13.2. Informative References . . . . . . . . . . . . . . . . . . 21
   Appendix A.  Examples Log Format . . . . . . . . . . . . . . . . . 22
     A.1.  W3C Common Log File (CLF) Format . . . . . . . . . . . . . 22
     A.2.  W3C Extended Log File (ELF) Format . . . . . . . . . . . . 23
     A.3.  National Center for Supercomputing Applications (NCSA)
           Common Log Format  . . . . . . . . . . . . . . . . . . . . 24
     A.4.  NCSA Combined Log Format . . . . . . . . . . . . . . . . . 24
     A.5.  NCSA Separate Log Format . . . . . . . . . . . . . . . . . 24
     A.6.  Squid 2.0 Native Log Format for Access Logs  . . . . . . . 25
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25



































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1.  Introduction

   This memo specifies the Logging interface between a downstream CDN
   (dCDN) and an upstream CDN (uCDN).  It introduces a framework, an
   architecture design and a set of new requirements.  Then it drafts an
   information model.

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

   o  CDNI problem statement [I-D.ietf-cdni-problem-statement] and
      framework [I-D.davie-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.

   The present document describes:

   o  The Logging framework (Section 2),

   o  The architecture (Section 3),

   o  The requirements (Section 4),

   o  Discussion on the monitoring and the reporting (Section 5)

   o  Log information (Section 6 and Section 7),

1.1.  Terminology

   We adopt the terminology described in
   [I-D.ietf-cdni-problem-statement] and [I-D.davie-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 CDNI Logging interface.

   Log: CDN internal information collection and processing operations.

   Logging: Inter-CDN information exchange and processing operations.

   Small object: [Ed.  Note: TBD]

   Fragmented object: [Ed.  Note: Tentative of a simple definition which



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   fits with the current CDNi charter] Fragmented objects are pieces of
   content provided by a CSP which are delivered individually through a
   CDN interconnection.  They differ from a simple object because the
   delivery of the content to one user agent may be provided by more
   than one Surrogate/CDN.

   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 differed time.  Such information typically includes
   aggregated data that can cover a large period of time (e.g., from
   hours to several months).  One of the usages of reporting is 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.  The monitoring typically includes data in real time to
   provide a vision 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.

   Core log information: minimal information that has to be logged to
   satisfy the Logging requirements

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

   Usage data: the usage data refers to all the information related to a
   specific end-user session.

   Delivery service: [Ed.  Note: to be defined]

1.2.  Abbreviations

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

   o  API: Application Programming Interface

   o  CDN: Content Delivery Network

   o  CDNP: Content Delivery Network Provider

   o  CoDR: Content Delivery Record

   o  CSP: Content Service Provider




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   o  DASH: Dynamic Adaptive Streaming over HTTP

   o  dCDN: downstream CDN

   o  FTP: File Transfer Protocol

   o  FTPS: FTP Secure

   o  HAS: HTTP Adaptive Streaming

   o  KPI: Key Performance Indicator

   o  PVR: Personal Video Recorder

   o  SNMP: Simple Network Management Protocol

   o  uCDN: upstream CDN


2.  Logging Framework

   The framework of the Logging interface is straightforward: dCDN logs
   any information related to the completion of any task performed by a
   dCDN on behalf of an uCDN and any exchange related to the management
   of the contents that the said dCDN delivers on behalf of an uCDN, as
   discussed in Section 7.1.


3.  Architecture

   Logging is a mandatory feature for a CDN, especially if the CDN is
   interconnected to other CDNs.  Logging provides the raw material for
   some essential operations of a delivery service, such as monitoring,
   reporting, billing, etc.

   As stated in [I-D.ietf-cdni-problem-statement], "the CDNI Logging
   interface enables details of logs or events to be exchanged between
   interconnected CDNs".

   Figure 1 provides an example of Logging information exchanges. uCDN
   is connected to dCDN-1 and dCDN-2.  Both dCDN-1, dCDN-2, and uCDN
   deliver content for CSP.  The Logging interface enables the uCDN to
   obtain Logging data from dCDN-1 and dCDN-2.  In the example, uCDN
   uses the Logging data:

   o  to audit the performance of the delivery operated by the dCDNs and
      to adjust its routing request as appropriate,




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

   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. uCDN may also provide Logging data as raw logs to
   CSP, so that CSP uses its own Logging analysis tools.



                      +-----+
                      | CSP |
                      +-----+
                         ^
                         |
                         | Reporting and monitoring data
                         | Billing
                         |
                      ,--,--.
                   ,-'       `-.
            CoDR  (     uCDN    )   CoDR
             ....>(             )<....
             |    (             )    |
             |    (     RRi     )    |
             |     `-. Tuning ,-'    |
             |         -|-|-'        |
             |          | |          |
             |          | |          |
          ,--|--.       | |       ,--|--.
       ,-'       `-.    | |    ,-'       `-.
      (   dCDN-1   <----+ + --->  dCDN-2    )
       `-.       ,-'           `-.       ,-'
         `--'--'                  `--'--'



                 Figure 1: Exchange of Logging Information

   Figure 2 presents the Logging Architecture.  More details on the
   Logging operations are provided in Section 8.  A dCDN prepares the
   CoDRs requested by the uCDN.  This preparation involves operations
   such as filtering, aggregating, anonymizing, and summarizing the
   logs.  The uCDN downloads the corresponding CoDRs and performs its
   own reporting for the CSP.







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   --------
  /        \
  |   CSP  |
  \        /
   --^-----
     ^
     ^ Reporting, Monitoring, Billing
     ^
  ---^---------------------                    -------------------------
 /   ^    Upstream CDN     \                  /    Downstream CDN       \
 |+-----+  +-------------+ |                  | +-------------+  +-----+|
 ||     |**|   Control   | |                  | |   Control   |**|     ||
 ||     |  +-------------+ |                  | +-------------+  | I   ||
 || I   |                  |  CoDR selection  |                  | n   ||
 || n   |  +-------------+ |----------------->| +-------------+  | t   ||
 || t   |<<|   Logging   | |                  | |   Logging   |<<| e   ||
 || e   |  +-------------+ |<-----------------| +-------------+  | r   ||
 || r   |                  |     CoDRs        |                  | c L ||
 || c L |                  |                  |                  | o o ||
 || o o |  +-------------+ |                  | +-------------+  | n g ||
 || n g |<<|Req-Routing  | |                  | |Req-Routing  |>>| n i ||
 || n i |  +-------------+ |                  | +-------------+  | e c ||
 || e c |                  |                  |                  | c   ||
 || c   |  +-------------+ |                  | +-------------+  | t   ||
 || t   |<<| Metadata    | |                  | | Metadata    |>>| i   ||
 || i   |  +-------------+ |                  | +-------------+  | o   ||
 || o   |                  |                  |                  | n   ||
 || n   |  +-------------+ |                  | +-------------+  |     ||
 ||     |<<| Distribution| |******************| | Distribution|>>|     ||
 |+-----+  +-------------+ |   Acquisition    | +-------------+  +-----+|
 \                         /                  \         . *             /
  -------------------------                    ---------.-*-------------
                .                                       . *
                .                               Request . * Delivery
                .                                       . *
                .                                    +--.-*--+
                ..................Request............| User  |
                                                     | Agent |
                                                     +-------+


                      Figure 2: Logging Architecture

   Logging Information elements may be captured at various stages during
   the lifecycle of content distribution.  The arrows (">>") of the
   above Figure 2 represent the direction of information elements in the
   Logging process.  They illustrate several important aspects:




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   o  An Information element may be captured either by an uCDN or a
      dCDN, or both;

   o  An Information element can be collected on another interface than
      the Logging (e.g., uCDN's Request-Routing);

   o  Information elements can be collected before the exchange of
      CoDRs.

   These points are further discussed in Section 9.


4.  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).

   [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.]


5.  Rationale for Logging Interface

   [I-D.davie-cdni-framework] and [I-D.ietf-cdni-problem-statement]
   already introduce the rationale for the Logging interface as a means
   for an uCDN to acquire some visibility on the contents the dCDN
   delivers on behalf of the uCDN. dCDN provides the uCDN with elements
   of information and CoDRs for operating the CDN interconnection and
   reporting to the CSP.  This section develops use cases that require
   exchange of Logging information.

5.1.  Usages of CDNI Logging Information By uCDN

   This section presents the usage of the CoDRs by an uCDN.  It does not
   make any assumption on where the CoDRs are produced.  CoDRs may be
   produced either by the uCDN or a dCDN.

5.1.1.  Maintenance/Debugging

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

   To detect faults, Logging must enable the reporting of any CDN
   operation success and failure, such as request redirection, content
   acquisition, etc.  Such information can be summarized into KPIs.  For



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   instance, Logging format should allow the computation of the number
   of times during a given epoch, a content delivery related to a
   specific service succeeds/fails.

   This need is taken into account in the events triggering log entries,
   which are listed in Section 7.

   Logging is useful to analyze the performance of content delivery
   services.  This implies computing KPIs from the Logging data for
   service quality analysis and monitoring (see Section 5.3).

   Logging enables the CDN providers to evaluate the QoS level related
   to a specific delivery service.  For instance, one aspect of this QoS
   level could be measured through the average delivery throughput
   experienced by end-users in a given region for this specific service
   over a period of time.

   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.

5.1.2.  Accounting

   Logging is essential for accounting, to permit inter-CDN billing, and
   CSP billing by uCDN.  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.

5.1.3.  End-User Experience Management

   The goal of end-user experience management is to gather any relevant
   information to meter audience, analyze user behavior, etc.  For
   instance, Logging enables the CDN providers to report on content
   consumption (e.g., delivered sessions per content) in a specific
   geographic area.

5.1.4.  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, access
   to content is usually collected to permit the CSP to detect
   infringements of content delivery policies and other abnormal end-



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   user behaviors.

5.2.  Logging Information Views

   Logging information is useful to the uCDN and potentially to the CSP.
   Different views of the Logging information may be provided depending
   on privacy, business, and scalability constraints.  Some kind of
   information format adaptation capability MAY be supported by an uCDN
   to present some (e.g., filtered, aggregated) data in the appropriate
   format (raw logs, reports) to the CSP.  More details on these
   operations are provided in Section 8.

   We provide a non-exhaustive list and description of tools that can be
   fed with Logging information.

   o  Tools used by the uCDN's operator: billing tools (information
      system), customer experience intelligence, reporting tools,
      security auditing tools, dimensioning tools, strategic planning
      and investment...

   o  Tools used by CSPs: customer experience management tools,
      reporting tools, security auditing tools...

5.3.  Information Extracted From Logging Data

   This section presents, for explanatory purposes, a non-exhaustive
   list of information that can be extracted/produced from logs.
   Depending on the inter-CDN agreement, this information may be
   computed by the uCDN or by the dCDN.

   CSPs require specific information, such as KPIs, about the delivery
   of their content.  The Logging data must contain appropriate
   information to enable CSPs or the uCDN to extract the required KPIs.
   In the present section, we list 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 delivery premature 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
      of time (e.g., hour/day/week/month)

   o  Top 10 of the most popular requested content (with time
      repartition into 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.


6.  Log Information Elements

   CDNI must specify a set of Logging information elements to avoid log
   format regeneration, which would affect the performance of the log
   handling chain.  A common set of Logging information element eases
   the sharing of logs among the CDNs and the use of log processing
   tools, for instance, to prepare reporting.

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





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6.1.  Core Information Elements

   This section describes a set of information elements that structure
   log information generated by the dCDN.  The section does not
   prescribe a particular encoding (such as SNMP SMI or alternatives).
   All fields in the log information are optional unless stated
   otherwise.

   +--------+----------------------------------------------------------+
   | Name   | Description                                              |
   +--------+----------------------------------------------------------+
   | Time   | A date and time associated with a logged event.  For     |
   |        | instance, the time that the server finished processing   |
   |        | the request.                                             |
   | URI_lo | The requested URL path (e.g.,                            |
   | 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/potter. |
   |        | avi?param=11&user=toto").  The URI without hostname      |
   |        |  typically includes the "CDN domain" (ex.cdn.csp.com) -  |
   |        |  cf. [I-D.davie-cdni-framework]: it enables the          |
   |        |  identification of the CSP service agreed between the CS |
   |        | Pand the CDNP operating the uCDN.                        |
   | Protoc | The protocol and protocol version of the message that    |
   | ol     | triggered the log entry.                                 |
   | Reques | The protocol method of the request message that          |
   | t      | triggered the log entry.                                 |
   |  metho |                                                          |
   | d      |                                                          |
   | Status | The protocol method of the reply message related to the  |
   |        | log entry                                                |
   | Body   | The number of bytes in the body of the reply message     |
   | size   | related to the log entry.  It does not include the size  |
   |        | of the response headers.                                 |
   | Bytes  | The number of bytes (headers + body) of the message that |
   | receiv | triggered the log entry.                                 |
   | ed     |                                                          |
   | Header | Multiple header fields, such as User Agent or Referrer,  |
   | s      | could be reproduced in the log entries.                  |
   | Durati | The duration of an operation in milliseconds.  For       |
   | on     | instance, this field could be used to provide the time   |
   |        | it took to 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.                  |
   | Operat | The kind of operation that is logged; for instance,      |
   | ion    | Acquisition, Delivery, or Purging.                       |
   +--------+----------------------------------------------------------+




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                    Table 1: Core Information Elements

   Subsequent table illustrates the definition of the core information
   elements.  It provides examples using Apache log format strings
   [apache] when they exist.  The table is here for illustration and
   does not prescribe a specific encoding.

   +----------+-------------------+------------------------------------+
   | Name     | String            | Example                            |
   +----------+-------------------+------------------------------------+
   | Time     | %t                | [10/Oct/2000:13:55:36 -0700]       |
   | URI_log  | -                 | -                                  |
   | Protocol | %H                | HTTP/1.0                           |
   | Request  | %m                | GET                                |
   | method   |                   |                                    |
   | Status   | %>s               | 200                                |
   | Body     | %b                | 2326                               |
   | size     |                   |                                    |
   | Bytes    | -                 | -                                  |
   | received |                   |                                    |
   | Header   | \"%{Referer}i\"   | "http://www.example.com/start.html |
   |          | \"%{User-agent}i\ | ""Mozilla/4.08 [en] (Win98; I      |
   |          | "                 |  ;Nav)"                            |
   | Duration | -                 | -                                  |
   | Operatio | -                 | -                                  |
   | n        |                   |                                    |
   +----------+-------------------+------------------------------------+

                   Table 2: Examples using Apache format

6.2.  Information Elements for Content Delivery

   +-------------+-----------------------------------------------------+
   | Name        | Definition                                          |
   +-------------+-----------------------------------------------------+
   | uCDN        | An element authenticating the operator of the uCDN  |
   | identifier  | as the authority having delegated the request to    |
   |             | the dCDN                                            |
   | End-user's  | The IP address of the client making a content       |
   | IP address  | delivery request (or of its proxy)                  |
   | Cache bytes | The number of body bytes served from caches.  This  |
   |             | quantity permits the computation of the byte hit    |
   |             | ratio.                                              |
   +-------------+-----------------------------------------------------+

                  Table 3: Delivery Information Elements





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6.3.  Information Elements for Content Acquisition

   +------------+------------------------------------------------------+
   | Name       | Definition                                           |
   +------------+------------------------------------------------------+
   | dCDN       | An element authenticating the operator of the dCDN   |
   | identifier | as the authority requesting the content to the uCDN  |
   +------------+------------------------------------------------------+

                 Table 4: Acquisition Information Elements

6.4.  Log Extensibility

   Future usages might introduce the need for additional Logging data.
   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 than the standard ones, if they
   want.


7.  Core Logging Records

   This section defines a set of central events that a dCDN should
   register and publish through the Logging interface.  There are two
   types of events.  The fist category belongs to legacy Web servers'
   access and errors logs.  The second is directly tied to the auditing
   of the CDN interconnection.

   We classify the logged events depending on the CDN operation to which
   they relate: content delivery, content acquisition, content purging,
   etc.

   Next versions of the memo will associate a CoDR to each event.

7.1.  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 log detailing the
   content delivery/content acquisition authorizations and denials as
   well as information on why the request is authorized/denied.

   The events triggering the generation of a log record include:

   o  Reception of a content request,




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   The generated log record typically embeds information about:

   o  Denial of delivery (error or unauthorized request) 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),

7.2.  Content Acquisition

   In case the uCDN require the dCDN to log acquisition related events,
   the events triggering the generation of a log 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 log 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 typically does not require the dCDN to log
   acquisition related events.

7.3.  Content Purging

   The purging of a piece of content is typically requested by the uCDN,
   which can, therefore, log events related to purging.  In case the
   uCDN nevertheless requests a dCDN to log purging events, the events
   triggering the generation of a log record include:

   o  Reception of a content purging request

   The generated log record typically embeds information about:

   o  Denial of the purging request (error or unauthorized request),

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




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   o  End of an authorized purging (success),

   o  End of an authorized purging (failure),

7.4.  Extended CoDRs

   The required Logging information 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 different services
   as well as future services, the Logging interface should support
   optional log information.


8.  Logging Process

   We walk through a "day in the life" of a CDN interconnection to
   present functions the two CDNs may require to exchange Logging
   information.  This will serve to illustrate many of the functions
   that could be supported through CDNI Logging interface.  We describe
   capabilities, such as log aggregation, anonymization, and filtering,
   that might be added to CDNI in a later stage, to optimize Logging
   operations.

8.1.  Logging Aggregation

   CDNs typically handle millions of records per day.  The processing of
   these records to extract relevant monitoring and reporting
   information is expensive in terms of CPU and time.  Therefore, as
   stated in [I-D.davie-cdni-framework], "a design tradeoff in the
   Logging interface is the degree of aggregation or summarization of
   data."

   In particular, dCDNs aggregate the logs of their elements (e.g., the
   Surrogates) to avoid both the complexity of distributing multiple log
   files to the uCDN and to avoid disclosing information about dCDN's
   internal topology.  This aggregation alleviates the Logging
   processing burden for the uCDN.

   [Ed.  Note: In a later version, the draft will propose methods to
   optimize the amount of information transmitted: (e.g., transmit only
   KPIs, use multiple levels of logs granularity such as in Apache
   (debug, notice, etc.)]





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8.1.1.  Logging and Fragmented Objects

   Many situations lead to the delivery of fragments of content (DASH,
   failure of delivery, partial delivery, PVR actions, etc.).  A dCDN
   may not publish a CoDR for each piece of content it delivers, because
   this can lead to unacceptably large logs.  In particular, a CoDR
   could provide aggregated information about the delivery of several
   content pieces. uCDN and dCDN must be able to agree on a level of
   granularity for the CoDRs.  This problem is well described for the
   case of HTTP adaptive streaming in [I-D.davie-cdni-framework]:

   "Most schemes to deliver HTTP-based adaptive bit- rate video use a
   large number of relatively small HTTP requests (e.g., one request per
   3-second chunk of video.)  It may be desirable to aggregate Logging
   information so that a single log entry is provided for the entire
   video rather than for each chunk.  Note however that such aggregation
   requires a degree of application awareness in dCDN to recognize that
   the many HTTP requests correspond to a single video."

8.2.  Logging Protection

8.2.1.  Logging Signing

   CDNs need guarantees on logs Integrity.  They want to know:

   o  who issued the Logging, and

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

   This is extremely important, as the logs can provide a basis for
   accounting/billing.

   [Ed. note: propose a mechanism to authenticate the Logging origin]

   [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."]

8.3.  Logging Filtering

   The dCDN must be able to present only relevant information to the
   uCDN, to avoid unnecessary log processing load for the uCDN.  Hence,
   the downstream CDN filters its logs, and passes the relevant records



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   directly to each upstream CDN.  This requires that the downstream CDN
   can recognize the set of log entries that relate to each upstream
   CDN, for instance thanks to the "uCDN identifier" information element
   Table 3.

   The dCDN must be able to filter some internal scope data 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 dCDN must be able to filter confidential data on the
   dCDN's topology (number of servers, location, etc.).  In particular,
   information about the requests served by every Surrogate is
   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.

8.4.  Logging Update and Rectification

   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 tradeoff between the Logging generation delay and the Logging
   accuracy.  Such mechanism would be particularly invaluable for real
   time Logging, which must be provided rapidly and cannot wait for the
   end of operations in progress.


9.  Protocols for Logging

   This section discusses the encoding and the protocols for
   transporting Logging information.

   CDNs usually store the logs in a format similar to the ones in use by
   web servers, such as W3C, NCSA, and Squid's log format, which are
   described in Appendix A.

   As presented in [I-D.ietf-cdni-problem-statement], several protocols
   already exist that could potentially be used to exchange CDNI Logging
   between interconnected CDNs.  The dCDN could publish non real-time
   Logging on a server where the uCDN would retrieve it using FTP, FTPS,



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   or Syslog.  If the CDNs need to exchange real-time information
   through the Logging interface, they could potentially rely on Web
   APIs, syslog, SNMP...  However, as explained in
   [I-D.ietf-cdni-problem-statement], "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."

   [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.]


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 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



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   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.

13.2.  Informative References

   [CLF]      A. Luotonen, "The Common Logfile 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]
              Bertrand, G., Faucheur, F., and L. Peterson, "Content
              Distribution Network Interconnection (CDNI) Experiments",
              draft-bertrand-cdni-experiments-01 (work in progress),
              August 2011.

   [I-D.davie-cdni-framework]
              Davie, B. and L. Peterson, "Framework for CDN
              Interconnection", draft-davie-cdni-framework-01 (work in
              progress), October 2011.

   [I-D.ietf-cdni-problem-statement]
              Niven-Jenkins, B., Faucheur, F., and N. Bitar, "Content
              Distribution Network Interconnection (CDNI) Problem
              Statement", draft-ietf-cdni-problem-statement-03 (work in
              progress), January 2012.

   [I-D.ietf-cdni-requirements]
              Leung, K. and Y. Lee, "Content Distribution Network
              Interconnection (CDNI) Requirements",
              draft-ietf-cdni-requirements-02 (work in progress),
              December 2011.

   [I-D.ietf-cdni-use-cases]
              Gilles, B., Emile, S., Watson, G., Burbridge, T., Eardley,
              P., and K. Ma, "Use Cases for Content Delivery Network
              Interconnection", draft-ietf-cdni-use-cases-03 (work in
              progress), January 2012.



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   [RFC3444]  Pras, A. and J. Schoenwaelder, "On the Difference between
              Information Models and Data Models", RFC 3444,
              January 2003.

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

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

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

   [squid]    "Squid LogFormat documentation", Feb. 2012, <http://
              wiki.squid-cache.org/Features/
              LogFormat?highlight=%28\\bCategoryFeature\\b%29|%
              28faqlisted.yes%29>.


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 logfile 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]:




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   +------------+------------------------------------------------------+
   | 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.                                              |
   | 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.



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   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.  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"

   The format of the Referral log is as follows:

   o  date:time agent




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

   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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Authors' Addresses

   Gilles Bertrand (editor)
   France Telecom - Orange
   38-40 rue du General Leclerc
   Issy les Moulineaux,   92130
   FR

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


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

   Email: emile.stephan@orange.com
































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