Apache Reference: http_core, LimitRequestFields
Limit Maximum Number of Request Fields
Syntax: LimitRequestFields A
Example: LimitRequestFields 20
Since: Apache 1.3
The directive specifies the maximum number of header fields that can
appear in a request message.
The number argument is an integer from 0 (meaning unlimited)
to 32,767 (32 KB). The directive allows a server administrator
to modify the limit on the number of request header fields
allowed in an HTTP request. This value should be
larger than the number of fields that a normal client request
might include. Use of this directive gives the server administrator
greater control over abnormal client request behavior, which help
prevent some forms of denial-of-service attacks.