Apache Reference: http_core, LimitRequestFieldsize
Limit Maximum Size of Request Fields
Syntax: LimitRequestFieldsize A
Example: LimitRequestFieldsize 8190
Since: Apache 1.3
This directive specifies the maximum size of an HTTP request header field. The
bytes argument is an integer from 0 (meaning unlimited)
to 8,190 (slightly less than 8KB). The directive allows a server
administrator to reduce the allowed size of an HTTP
request header field below the normal input buffer size compiled
with the server. This value should be large enough
to hold any one header field from a normal client request.
Use of this directive gives the server administrator greater control
over abnormal client request behavior, which may help prevent
some forms of denial-of-service attacks.