114 Citrix NetScaler Policy Configuration and Reference Guide
About Evaluating HTTP and TCP Payload
The payload of an HTTP request or response consists of header fields, URLs, the
body content, the version, status, and so on. For example, the following
expression performs a simple matching operation on an HTTP request to
determine if it contains a header named “myHeader”:
http.req.header("myHeader").exists
The following example compound expression evaluates HTTP headers. You
could use the following expression in various NetScaler features, such as
Integrated Caching, Rewrite, and Responder:
(http.req.header("Content-Type").exists && http.req.
header("Content-Type").eq("text/html")) || (http.req.
header("Transfer-Encoding").exists) || (http.req.
header("Content-Length").exists)
The payload of a TCP or UDP packet is the data portion of the packet. You can
configure advanced expressions to examine features of a TCP or UDP packet,
including the following:
• Source and destination domains
• Source and destination ports
• The text in the payload
• Record types

About Evaluating the Payload Body

There are three expression prefixes that extract text from the body of the payload,
as follows:
•HTTP.REQ.BODY(integer). Returns the body of an HTTP request as
a multiline text object, up to the character position designated in the integer
argument. If there are fewer characters in the body than is specified in the
argument, the entire body is returned.
•HTTP.RES.BODY(integer). Returns a portion of the HTTP response
body. The length of the returned text is equal to the number in the integer
argument. If there are fewer characters in the body than is specified in
integer, the entire body is returned.
•CLIENT.TCP.PAYLOAD(integer). Returns TCP payload data as a
string, starting with the first character in the payload and continuing for the
number of characters in the integer argument.