The W3C Extended log file format is the default log file format for IIS. It is a customizable ASCII text-based format. You can use IIS Manager to select which fields to include in the log file, which allows you to keep log files as small as possible. Because HTTP.sys handles the W3C Extended log file format, this format records HTTP.sys kernel-mode cache hits.
Table 10.1 lists and describes the available fields. Default fields are noted.
Table 10.1 W3C Extended Log File Fields
Field Appears As Description Default Y/N
Date
date
The date on which the activity occurred.
Y
Time
time
The time, in coordinated universal time (UTC), at which the activity occurred.
Y
Client IP Address
c-ip
The IP address of the client that made the request.
Y
User Name
cs-username
The name of the authenticated user who accessed your server. Anonymous users are indicated by a hyphen.
Y
Service Name and Instance Number
s-sitename
The Internet service name and instance number that was running on the client.
N
Server Name
s-computername
The name of the server on which the log file entry was generated.
N
Server IP Address
s-ip
The IP address of the server on which the log file entry was generated.
Y
Server Port
s-port
The server port number that is configured for the service.
Y
Method
cs-method
The requested action, for example, a GET method.
Y
URI Stem
cs-uri-stem
The target of the action, for example, Default.htm.
Y
URI Query
cs-uri-query
The query, if any, that the client was trying to perform. A Universal Resource Identifier (URI) query is necessary only for dynamic pages.
Y
HTTP Status
sc-status
The HTTP status code.
Y
Win32 Status
sc-win32-status
The Windows status code.
N
Bytes Sent
sc-bytes
The number of bytes that the server sent.
N
Bytes Received
cs-bytes
The number of bytes that the server received.
N
Time Taken
time-taken
The length of time that the action took, in milliseconds.
N
Protocol Version
cs-version
The protocol version —HTTP or FTP —that the client used.
N
Host
cs-host
The host header name, if any.
N
User Agent
cs(User-Agent)
The browser type that the client used.
Y
Cookie
cs(Cookie)
The content of the cookie sent or received, if any.
N
Referrer
cs(Referrer)
The site that the user last visited. This site provided a link to the current site.
N
Protocol Substatus
sc-substatus
The substatus error code.
Y
For information about status codes, see IIS Status Codes.
 Note
FTP log files do not record the following fields:
•
cs-uri-query
•
cs-host
•
cs(User-Agent)
•
cs(Cookie)
•
cs(Referrer)
•
sc-substatus
You can select as many of the W3C Extended log file fields as you want. However, not all fields will contain information. For fields that are selected but for which there is no information, a hyphen (-) appears as a placeholder. If a field contains a nonprintable character, HTTP.sys replaces it with a plus sign (+) to preserve the log file format. This typically occurs with virus attacks, when, for example, a malicious user sends carriage returns and line feeds that, if not replaced with the plus sign (+), would break the log file format.
Fields are separated by spaces. Field prefixes have the following meanings:
•
s- Server actions
•
c- Client actions
•
cs- Client-to-server actions
•
sc- Server-to-client actions
 Note
For the time-taken field, the client-request timestamp is initialized when HTTP.sys receives the first byte, but before HTTP.sys begins parsing the request. The client-request timestamp is stopped when the last IIS send completion occurs. Time taken does not reflect time across the network. The first request to the site shows a slightly longer time taken than other similar requests because HTTP.sys opens the log file with the first request.