Citrix Systems Network Router 9.2 User Manual

A callout to an external application consists of an HTTP request and a set of 
parameters that parse the response to the request. You configure the entire 
request, or significant parameters in the request, in the HTTP callout policy. The 
HTTP callout policy also contains information about the recipient of the request 
and advanced expressions for parsing the HTTP response when it is received.

A callout can send only an HTTP request. The service can only be an HTTP or 
HTTPS service.

After configuring an HTTP callout policy, you do not bind it or add it to a policy 
bank, as you would another policy. Instead, you invoke it using an advanced 
expression in one of the following:

•

Content Switching: For content switching of HTTP and TCP data

•

Rewrite 

•

Responder: For content filtering functions

•

Load Balancing: For token-based load balancing

1.

Create a callout policy in the Rewrite feature, as described in 

.

2.

In the feature where the callout policy is needed, invoke the callout policy 
from an advanced expression, as described in 

3.

Configure an HTTP callout agent to format the callout to the receiving 
application, as described in the “HTTP Service Callout” chapter in the 
Citrix NetScaler AppExpert Guide.

You configure HTTP callout policies in the Rewrite feature. After you define the 
callout policy, it can be invoked from a policy expression in other NetScaler 
features. For information on configuring the callout policy, see 

. For information on invoking the callout 

policy, see 

.

An HTTP callout policy contains the following components:

•

Parameters that identify the application to be queried.