When NetScaler gets an HTTP request that includes the Expect: 100-Continue header, it sends a 100 Continue response back to the client. This step is important because NetScaler’s Application Firewall needs to review the full request—including the body—before passing it on to the backend server.

After the client receives the 100 Continue response, it sends the rest of the request (the body). NetScaler then checks the entire request using its firewall rules. Once that's done, it forwards the request to the backend server.

At this point, NetScaler changes or removes the original Expect: 100-Continue header, since it’s no longer needed after the full request has already been processed.

 

 

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Instructions

Detailed Breakdown:

• Expect: 100-Continue Header:
  This header indicates that the client expects a 100 Continue response from the server before sending the request body.

 

• NetScaler’s Role:
  Acting as a proxy, NetScaler immediately responds with a 100 Continue status when it encounters this header, prompting the client to send the request body.

 

• Client Sends Remaining Request:
  Upon receiving the 100 Continue response, the client sends the rest of the request data (i.e., the body).

 

• NetScaler Processing and Forwarding:
  NetScaler intercepts the complete request, applies the necessary Application Firewall rules, and then forwards it to the backend server.

 

• Header Modification:
  During this process, NetScaler modifies the Expect: 100-Continue header—often by changing its format or value—to ensure it does not affect backend processing.

 

• Backend Server Behavior:
  The backend server typically ignores any altered or unrecognized headers, including the modified Expect: 100-Continue, as it has already received the complete request.

This article explains how NetScaler handles HTTP requests containing the Expect: 100-Continue header. It details the process where NetScaler responds with a 100 Continue status, inspects the full request through its Application Firewall, and then forwards it to the backend server after modifying or removing the now-unnecessary header. The step-by-step breakdown highlights each stage of the request handling and how NetScaler ensures secure and proper processing before reaching the backend.