CDNI Logging Interface
draft-bertrand-cdni-logging-01
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| Last updated | 2012-08-10 | ||
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draft-bertrand-cdni-logging-01
Internet Engineering Task Force G. Bertrand, Ed.
Internet-Draft E. Stephan
Intended status: Informational France Telecom - Orange
Expires: February 11, 2013 R. Peterkofsky
Skytide, Inc.
August 10, 2012
CDNI Logging Interface
draft-bertrand-cdni-logging-01
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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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 5
2. Logging Framework and Architecture . . . . . . . . . . . . . . 6
3. Additional Requirements . . . . . . . . . . . . . . . . . . . 10
4. Rationale for Logging Interface . . . . . . . . . . . . . . . 10
4.1. Usages of CDNI Logging Information . . . . . . . . . . . . 10
4.1.1. Maintenance/Debugging . . . . . . . . . . . . . . . . 10
4.1.2. Accounting . . . . . . . . . . . . . . . . . . . . . . 11
4.1.3. End-User Experience Management . . . . . . . . . . . . 11
4.1.4. Security . . . . . . . . . . . . . . . . . . . . . . . 11
4.1.5. Legal Logging Duties . . . . . . . . . . . . . . . . . 11
4.2. Logging Information Views . . . . . . . . . . . . . . . . 11
4.3. Information Extracted From Logging Data . . . . . . . . . 12
5. Log Information Elements . . . . . . . . . . . . . . . . . . . 13
5.1. Information Elements . . . . . . . . . . . . . . . . . . . 13
5.2. Logging Record Information Elements for Content
Delivery . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.3. Logging Record Information Elements for . . . . . . . . . 17
5.4. Logging Record Information Elements for Other
Operations . . . . . . . . . . . . . . . . . . . . . . . . 17
6. Core Logging Records . . . . . . . . . . . . . . . . . . . . . 18
6.1. Content Delivery . . . . . . . . . . . . . . . . . . . . . 18
6.2. Content Acquisition . . . . . . . . . . . . . . . . . . . 18
6.2.1. Logging Records Provided by dCDN to uCDN . . . . . . . 18
6.2.2. Logging Records Provided by uCDN to dCDN . . . . . . . 19
6.3. Content Invalidation and Purging . . . . . . . . . . . . . 19
6.4. Logging Extensibility . . . . . . . . . . . . . . . . . . 20
7. Default Logging Information Format . . . . . . . . . . . . . . 20
7.1. Logging Files . . . . . . . . . . . . . . . . . . . . . . 20
7.2. File Format . . . . . . . . . . . . . . . . . . . . . . . 20
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7.2.1. Headers . . . . . . . . . . . . . . . . . . . . . . . 21
7.2.2. Body (Logging Records) Format . . . . . . . . . . . . 21
7.2.3. Footer Format . . . . . . . . . . . . . . . . . . . . 22
8. Logging Format and Scope Negotiation . . . . . . . . . . . . . 22
9. Logging Information Transport . . . . . . . . . . . . . . . . 22
9.1. Major Requirements on Logging Protocols . . . . . . . . . 23
9.2. Recommended Logging Protocol for Non Real-Time Logging . . 23
9.3. Recommended Logging Protocol for Real-Time Logging . . . . 24
10. Logging Process . . . . . . . . . . . . . . . . . . . . . . . 24
10.1. Logging Aggregation . . . . . . . . . . . . . . . . . . . 24
10.2. Logging Filtering . . . . . . . . . . . . . . . . . . . . 25
10.3. Logging Update and Rectification . . . . . . . . . . . . . 26
11. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 26
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
13. Security Considerations . . . . . . . . . . . . . . . . . . . 27
13.1. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 27
13.2. Non Repudiation . . . . . . . . . . . . . . . . . . . . . 27
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
15.1. Normative References . . . . . . . . . . . . . . . . . . . 28
15.2. Informative References . . . . . . . . . . . . . . . . . . 28
Appendix A. Examples Log Format . . . . . . . . . . . . . . . . . 29
A.1. W3C Common Log File (CLF) Format . . . . . . . . . . . . . 29
A.2. W3C Extended Log File (ELF) Format . . . . . . . . . . . . 30
A.3. National Center for Supercomputing Applications (NCSA)
Common Log Format . . . . . . . . . . . . . . . . . . . . 32
A.4. NCSA Combined Log Format . . . . . . . . . . . . . . . . . 32
A.5. NCSA Separate Log Format . . . . . . . . . . . . . . . . . 32
A.6. Squid 2.0 Native Log Format for Access Logs . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
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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.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.
o [I-D.lefaucheur-cdni-logging-delivery] complements the present
memo by proposing CDNI Logging formats for content deliveries
performed using HTTP or HTTP adaptive streaming.
The present document describes:
o The Logging framework and architecture (Section 2),
o The requirements (Section 3),
o Discussion on the monitoring and the reporting use cases
(Section 4)
o Log information (Section 5 and Section 6),
1.1. Terminology
In this document, the first letter of each CDNI-specific term is
capitalized. We adopt the terminology described in
[I-D.ietf-cdni-problem-statement] 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 CDNI Logging interface.
Log and Logging formats may be different.
Log: CDN internal information collection and processing operations.
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Logging: Inter-CDN information exchange and processing operations.
Fragmented object: [Ed. Note: Tentative of a simple definition which
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.
End-User experience management: study of Logging data using
statistical analysis to discover, understand, and predict user
behavior patterns.
Delivery Service: a specific instantiation of content delivery
service configuration. For instance, a given uCDN (uCDN1) may
request a given dCDN (dCDN1) to configure a 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 request for static pictures delegated by uCDN1 and related
to CSP1. In this simple example, uCDN1 may request dCDN1 to include
delivery service information in its CDNI Logging, to help uCDN
provide relevant reports to CSP1.
1.2. Abbreviations
o API: Application Programming Interface
o CCID: Content Collection Identifier
o CDN: Content Delivery Network
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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. Logging Framework and Architecture
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 6.1.
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
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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.
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 log
files to CSP, so that CSP uses its own Logging analysis tools.
+-----+
| CSP |
+-----+
^ Reporting and monitoring data
| Billing
,--,--.
Logging ,-' `-. Logging
Data ( uCDN ) Data
....> `-. _,-'<....
| `-'-'-' |
,--v--. ^ ^ ,--v--.
,-' `-. | | ,-' `-.
( dCDN-1 )<--+ +-->( dCDN-2 ) Logging
`-. ,-' Logging `-. _,-'<...Data
`--'--' Tuning `--'-' |
^ ,--|--.
Logging | ,' `-.
Tuning + -->( dCDN-3 )
`. ,-'
`--'--'
Figure 1: Exchange of Logging Information
A dCDN integrates the logging of its downstream CDNs in the Logging
that it provides to the uCDN, as required by
[I-D.ietf-cdni-requirements] (LOG-3).
Figure 1 represents bi-directional arrows between dCDN and uCDN for
the exchange of Logging data, because even if the common case
involves the uCDN retrieving Logging data on the dCDN, the reverse
case where the dCDN retrieves Logging data (e.g., related to dCDN's
content acquisition requests to the uCDN) on the uCDN is also
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possible.
Note that the format of Logging data that the dCDN provides might be
different from the one that the dCDN uses internally. In this case,
the dCDN needs to reformat the Logging data before it provides this
data to the uCDN. Similarly, an uCDN might reformat the Logging data
that it receives before providing it to the CSP or to its uCDN. Such
reformatting operations are time consuming (delays in the Logging
chain) and introduce a processing burden. Therefore, it is
recommended that the CDNI Logging format be as close as possible from
the most common CDN Log formats.
Figure 2 presents the Logging Architecture. More details on the
Logging operations are provided in Section 10. A dCDN prepares the
Logging data requested by the uCDN. This preparation involves
operations such as filtering, aggregating, anonymizing, and
summarizing the logs. The uCDN downloads the corresponding Logging
Records and performs its own reporting for the CSP.
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+------+
| CSP |
+------+
^
^ Reporting, Monitoring, Billing
^
---^--------------------- Logging Record -------------------------
/ ^ Upstream CDN \ selection / Downstream CDN \
|+-----+ +-------------+ | and format nego. | +-------------+ +-----+|
|| |**| Control | |<---------------->| | Control |**| ||
|| | +-------------+ | | +-------------+ | I ||
|| I | | | | n ||
|| n | +-------------+ | | +-------------+ | t ||
|| t |<<| Logging | | | | Logging |<<| e ||
|| e | +-------------+ |<---------------->| +-------------+ | r ||
|| r | | Logging Records | | 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
In Figure 2, the Logging Record selection and format negotiation
occurs at Control Interface level, as these operations provide static
information for initializing the Logging interface.
Logging data captures information elements that may be available at
various stages during the life-cycle of content distribution. The
arrows (">>") in Figure 2 represent the direction of information
elements in the Logging process.
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3. 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).
4. Rationale for Logging Interface
[I-D.ietf-cdni-framework] and [I-D.ietf-cdni-problem-statement]
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 Logging Records for operating the CDN interconnection
and reporting to the CSP. This section develops use cases that
require exchange of Logging information.
4.1. Usages of CDNI Logging Information
This section presents the usage of the Logging Records by an uCDN.
It does not make any assumption on where the Logging Records are
produced. Logging Records may be produced either by the uCDN or a
dCDN.
4.1.1. 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. 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, a content delivery related to a
specific service succeeds/fails.
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 4.3).
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
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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.
4.1.2. 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.
4.1.3. 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.
4.1.4. 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-
User behaviors.
4.1.5. 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 requisitions.
4.2. 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 log files, reports) to the CSP. More details on these
operations are provided in Section 10.
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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...
4.3. 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. Nevertheless, 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.
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),
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
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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. Such KPIs are out of scope for the
present memo.
5. 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' 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.
5.1. Information Elements
This section describes a set of information elements that structure
Logging information generated by the dCDN. The section does not
prescribe a particular encoding (such as SNMP SMI or alternatives).
All fields in the Logging information are optional unless stated
otherwise. However, if a given CDN decides to support some of the
Logging information fields, it must conform to the definition and
format of this field specified in the present memo, to guarantee that
interconnected CDNs share a common understanding of the Logging
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semantic and syntax.
+-------------+-----------------------------------------------------+
| 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 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. |
| Client-IP | The IP address of the User Agent that issued the |
| | logged request (or of a proxy). |
| 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/po |
| | tter.avi?param=11&user=toto"). When HTTP request |
| | redirection is used, this URI includes the |
| | Surrogate FQDN. 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/po |
| | tter.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]: |
| | it enables the identification of the CSP service |
| | agreed between the CSP and the CDNP operating the |
| | uCDN. |
| Protocol | The protocol and protocol version of the message |
| | that triggered the Logging entry. |
| Request-met | The protocol method of the request message that |
| hod | triggered the Logging entry. |
| Status | The protocol method of the reply message related to |
| | the Logging entry |
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| Bytes-Trans | The number of bytes at application-layer |
| ferred | protocol-level (e.g., HTTP) of the reply message |
| | related to the Logging entry. It includes the size |
| | of the response headers. |
| Bytes-recei | The number of bytes (headers + body) of the message |
| ved | 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. |
| Record-dige | A digest of the Logging Record; it enables |
| st | detecting corrupted Logging Records. |
| 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: Logging Record Information Elements
NB: we define three fields related to the timing of logged
operations: Start-time, End-time, and Duration. Only two of these
three fields are required to obtain relevant timing information on
the operation. Start-time is typically useful for human readers
(e.g., while debugging), however, most servers log the operations
End-time which correspond to the time of log record generation.
Multiple header fields, in addition to User Agent and Referrer, could
be reproduced in the Logging entries.
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 Inter-
Affiliates scenarios [I-D.ietf-cdni-use-cases]. However, in some
cases it may be considered as confidential and the dCDN may provide
URI_part instead.
Table 2 illustrates the definition of the information elements. It
provides examples using Apache log format strings [apache] when they
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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] |
| Duration | - | - |
| Client-IP | - | - |
| Operation | - | - |
| URI_log | - | - |
| Protocol | %H | HTTP/1.0 |
| Request | %m | GET |
| method | | |
| Status | %>s | 200 |
| Bytes | %O | 2326 |
| transferre | | |
| d | | |
| Bytes | - | - |
| received | | |
| Header | \"%{Referrer}i\" | "http://www.example.com/start.htm |
| | \"%{User-agent}i | l" "Mozilla/4.08 [en] (Win98; I |
| | \" | ;Nav)" |
+------------+------------------+-----------------------------------+
Table 2: Examples using Apache format
5.2. Logging Record Information Elements for Content Delivery
Table 3 details specific Logging fields that dCDN may provide to uCDN
and that are related to content delivery operations.
+-------------------+-----------------------------------------------+
| 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. |
| End-User-IP | The IP address of the client making a content |
| | delivery request (or of its proxy). |
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| 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: Delivery Information Elements
5.3. Logging Record Information Elements for
Table 4 details specific Logging fields that are related to content
acquisition operations.
[Ed. Note: split this section in two parts: logs provided by uCDN /
logs provided by dCDN?]
+------------+------------------------------------------------------+
| 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
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.
5.4. Logging Record Information Elements for Other Operations
Logging can be used for debugging. Therefore, all kind of CDN
operations might be logged, depending on the agreement between the
dCDN and the uCDN. In particular, operations related to Request
Routing, Metadata and Control interfaces can be logged.
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6. Core Logging Records
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.
6.1. 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 CDSP 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 (cf. Section 10.1).
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) 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).
6.2. Content Acquisition
6.2.1. 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:
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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 (except for security or debugging
reasons).
6.2.2. 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).
6.3. 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:
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o Denial of the invalidation/purging request (error or unauthorized
request),
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).
6.4. 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.
7. Default Logging Information Format
Interconnected CDNs may support various Logging formats. However,
they must support at least the default Logging format described here.
7.1. 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 will be
detailed in future versions.]
7.2. File Format
[Ed. note: The Logging file format is not necessarily independant of
the selected transport protocol. The definition of the Logging file
format should be carried out consistently with the candidate protocol
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analysis for Logging transport. The present content of this section
is therefore non definitive.]
7.2.1. Headers
As initially proposed in [I-D.lefaucheur-cdni-logging-delivery],
Logging files must include a header with the information described in
Figure 3.
+----------------+-------------------+------------------------------+
| Field | Description | Examples |
+----------------+-------------------+------------------------------+
| Format | Identification of | standard_cdni_errors_http_v1 |
| | CDNI Log format. | |
| Fields | A description of | |
| | the records 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 3: Logging Headers
7.2.2. Body (Logging Records) Format
[Ed. note: the W3C extended log format is a good base candidate to
look at.]
[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
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[draft-caulfield-cdni-metadata-core-00]). Also see RFC5424 Section
6.2.3.]
[Ed. Note: Records used for real time information and non-real time
information could use different formats.]
7.2.3. Footer Format
As initially proposed in [I-D.lefaucheur-cdni-logging-delivery],
Logging files must include a footer with the information described in
Figure 4.
+---------+----------------------------------------------+----------+
| Field | Description | Examples |
+---------+----------------------------------------------+----------+
| Log | Digest of the complete Log (facilitates | |
| Digest | detection of Log corruption) | |
+---------+----------------------------------------------+----------+
Figure 4: Logging footers
8. Logging Format and Scope Negotiation
[Ed. Note: Format should be negotiated per 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.]
9. Logging Information Transport
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 for
example SSH File Transfer Protocol (SFTP). If the CDNs need to
exchange real-time information through the Logging interface, they
could potentially rely on Web APIs, Syslog, SNMP... The main
criterion for selecting a Logging transport protocol is the time
constraint for delivering the Logging. Therefore, the present
section highlights the candidate protocols for real-time and non
real-time Logging exchanges.
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9.1. Major Requirements on Logging Protocols
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. Finally, this protocol must comply with the
requirements identified in [I-D.ietf-cdni-requirements].
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).
This is extremely important, as the logs can provide a basis for
accounting/billing.
Logging also contains confidential data, and therefore, it should not
be protected from eavesdropping.
All these needs translate into security requirements on both the
Logging data format and on the Logging protocol.
[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."]
9.2. Recommended Logging Protocol for Non Real-Time Logging
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: timing constraints... cf LOG-6 offline vs. constrained
time / on demand access to real-time logging information]
[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
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information conveyed by the protocol, etc.]
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: event-triggered or periodic, why?]
[Ed. note: Propose protocol and add call flow]
9.3. Recommended Logging Protocol for Real-Time Logging
The uCDN must be able to retrieve real-time information via near
real-time methods such as: Syslog, SNMP, or through APIs, for
example.
[Ed. note: dCDN does not just forward requests for real time logging.
It should probably provide other (more complex?) information in real
time about the ongoing sessions (e.g., for every active session : IP
of the client, service, CDN name, content consumed (full URL),
average bit rate, downloaded size, date of session start?)
10. 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, anonymizing, and filtering,
that might be added to CDNI in a later stage, to optimize Logging
operations.
10.1. 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.ietf-cdni-framework], "a design tradeoff in the
Logging interface is the degree of aggregation or summarization of
data."
In particular, dCDNs must 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.
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Many situations also lead to the delivery of fragments of content
(DASH, failure of delivery, partial delivery, PVR actions, etc.). A
dCDN may not publish a Logging Record for each piece of content it
delivers, because this can lead to unacceptably large logs. In
particular, a Logging Record 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 Logging Records.
This problem is well described for the case of HTTP adaptive
streaming in [I-D.ietf-cdni-framework] and
[I-D.brandenburg-cdni-has].
In the current version of the draft, we identify the following
options that may be considered for reducing the amount of Logging
data.
o Transmit only summaries, for instance, a summary may aggregate
information of all deliveries that occur during a 5 minutes time
slot or provide only Logging data related to content items that
have been delivered at least a specific number of times. Note
that such aggregation leads to an information loss. This may be
problematic for some usages of Logging (e.g., debugging) and some
information should always be present, for instance, information
about content delivery errors (403,404,...). The use multiple
levels of Logging granularity such as in Apache (debug, notice,
etc.) may help in providing the most relevant amount of
information depending on the intended Logging usage, without
having to renegotiate the Logging format.
o For HAS content, a way to compress logs with minimal information
loss would be to merge all success 200 OK records Records related
to the same level of video Quality into a single record with
appropriate Start-time and End-time. The only information lost in
this process would be the Start-time and End-time for every video
chunk.
o Losslessly compress the Logging data.
o 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.
[Ed. Note: cite Syslog's concepts for aggregation ]
10.2. Logging Filtering
The dCDN must be able to present only relevant information to the
uCDN, to avoid unnecessary Logging processing load for the uCDN and
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potentially to protect End-Users' privacy. Hence, the downstream CDN
filters its logs, and passes the relevant records 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 host-names 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.
10.3. 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 trade-off between the Logging generation delay and the Logging
accuracy. Depending on the selected Logging protocol(s), such
mechanism may be particularly invaluable for real time Logging, which
must be provided rapidly and cannot wait for the end of operations in
progress.
11. Open Issues
The level of granularity of the date/time information must be
specified (clock accuracy).
When to log the end of a session when the End-User pauses a video
display?
[Ed. Note: check if all requirements are fulfilled by the proposed
solution]
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[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-Transferred, if there were aborted requests, do
those get counted as well? Not all client behavior can be correlated
with the simplified log.]
12. IANA Considerations
This memo includes no request to IANA.
13. Security Considerations
13.1. 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.
13.2. 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. Some of the security issues and requirements on
Logging are highlighted in Section 9.1.
14. 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
valuable inputs.
15. References
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15.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
15.2. 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-problem-statement]
Niven-Jenkins, B., Faucheur, F., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem
Statement", draft-ietf-cdni-problem-statement-08 (work in
progress), June 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
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progress), August 2012.
[I-D.lefaucheur-cdni-logging-delivery]
Faucheur, F., Viveganandhan, M., and K. Leung, "CDNI
Logging Formats for HTTP and HTTP Adaptive Streaming
Deliveries", draft-lefaucheur-cdni-logging-delivery-01
(work in progress), July 2012.
[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 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.
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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. |
| 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].
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+------------+---------------------------------------------------+
| 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.
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
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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 entries 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"
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.
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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
Squid also uses a "store log", which covers the objects currently
kept on disk or removed ones, for debugging purposes typically.
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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
Roy Peterkofsky
Skytide, Inc.
One Kaiser Plaza, Suite 785
Oakland CA 94612
USA
Phone: +01 510 250 4284
Email: roy@skytide.com
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