ServerName fully-qualified-domain-name 
Server config, virtual host

The ServerName directive sets the hostname of the server; this is used when creating redirection URLs. If it is not specified, then the server attempts to deduce it from its own IP address; however, this may not work reliably or may not return the preferred hostname. For example:

ServerName www.example.com

could be used if the canonical (main) name of the actual machine were simple.example.com, but you would like visitors to see www.example.com.

UseCanonicalName on|off
Default: on 
Server config, virtual host, directory, .htaccess

This directive controls how Apache forms URLs that refer to itself, for example, when redirecting a request for http://www.domain.com/some/directory to the correct http://www.domain.com/some/directory/ (note the trailing / ). If UseCanonical-Name is on (the default), then the hostname and port used in the redirect will be those set by ServerName and Port (not Apache v2). If it is off, then the name and port used will be the ones in the original request.

One instance where this directive may be useful is when users are in the same domain as the web server (for example, on an intranet). In this case, they may use the "short" name for the server (www, for example), instead of the fully qualified domain name (www.domain.com, say). If a user types a URL such as http://www/APACHE3/somedir (without the trailing slash), then, with UseCanonicalName switched on, the user will be directed to http://www.domain.com/somedir/. With UseCanonicalName switched off, she will be redirected to http://www/APACHE3/somedir/. An obvious case in which this is useful is when user authentication is switched on: reusing the server name that the user typed means she won't be asked to reauthenticate when the server name appears to the browser to have changed. More obscure cases relate to name/address translation caused by some firewalling techniques.

<LimitExcept method [method] ... > ... </LimitExcept>

<LimitExcept> and </LimitExcept> are used to enclose a group of access-control directives that will then apply to any HTTP access method not listed in the arguments; i.e., it is the opposite of a <Limit> section and can be used to control both standard and nonstandard/unrecognized methods. See the documentation for <Limit> for more details.

LimitRequestBody bytes
Default: LimitRequestBody 0
Server config, virtual host, directory, .htaccess

This directive specifies the number of bytes from 0 (meaning unlimited) to 2147483647 (2GB) that are allowed in a request body. The default value is defined by the compile-time constant DEFAULT_LIMIT_REQUEST_BODY (0 as distributed).

The LimitRequestBody directive allows the user to set a limit on the allowed size of an HTTP request message body within the context in which the directive is given (server, per-directory, per-file, or per-location). If the client request exceeds that limit, the server will return an error response instead of servicing the request. The size of a normal request message body will vary greatly depending on the nature of the resource and the methods allowed on that resource. CGI scripts typically use the message body for passing form information to the server. Implementations of the PUT method will require a value at least as large as any representation that the server wishes to accept for that resource.

This directive gives the server administrator greater control over abnormal client-request behavior, which may be useful for avoiding some forms of denial-of-service attacks.

LimitRequestFields number
Default: LimitRequestFields 100
Server config

number is an integer from 0 (meaning unlimited) to 32,767. The default value is defined by the compile-time constant DEFAULT_LIMIT_REQUEST_FIELDS (100 as distributed).

The LimitRequestFields directive allows the server administrator to modify the limit on the number of request header fields allowed in an HTTP request. A server needs this value to be larger than the number of fields that a normal client request might include. The number of request header fields used by a client rarely exceeds 20, but this may vary among different client implementations, often depending upon the extent to which a user has configured her browser to support detailed content negotiation. Optional HTTP extensions are often expressed using request-header fields.

This directive gives the server administrator greater control over abnormal client-request behavior, which may be useful for avoiding some forms of denial-of-service attacks. The value should be increased if normal clients see an error response from the server that indicates too many fields were sent in the request.

LimitRequestFieldsize bytes
Default: LimitRequestFieldsize 8190
Server config

This directive specifies the number of bytes from 0 to the value of the compile-time constant DEFAULT_LIMIT_REQUEST_FIELDSIZE (8,190 as distributed) that will be allowed in an HTTP request header.

The LimitRequestFieldsize directive allows the server administrator to reduce the limit on the allowed size of an HTTP request-header field below the normal input buffer size compiled with the server. A server needs this value to be large enough to hold any one header field from a normal client request. The size of a normal request-header field will vary greatly among different client implementations, often depending upon the extent to which a user has configured his browser to support detailed content negotiation.

This directive gives the server administrator greater control over abnormal client-request behavior, which may be useful for avoiding some forms of denial-of-service attacks. Under normal conditions, the value should not be changed from the default.

LimitRequestLine bytes
Default: LimitRequestLine 8190

This directive sets the number of bytes from 0 to the value of the compile-time constant DEFAULT_LIMIT_REQUEST_LINE (8,190 as distributed) that will be allowed on the HTTP request line.

The LimitRequestLine directive allows the server administrator to reduce the limit on the allowed size of a client's HTTP request line below the normal input buffer size compiled with the server. Since the request line consists of the HTTP method, URI, and protocol version, the LimitRequestLine directive places a restriction on the length of a request URI allowed for a request on the server. A server needs this value to be large enough to hold any of its resource names, including any information that might be passed in the query part of a GET request.

This directive gives the server administrator greater control over abnormal client-request behavior, which may be useful for avoiding some forms of denial-of-service attacks. Under normal conditions, the value should not be changed from the default.