Information on how the ARM changes packet addresses. See ARM redirection‚ on page 125.

A description of the appliance’s adaptive bypass scheme. See Appliance adaptive bypass‚ on page 126.

Serving requests transparently

Here’s how the Intel NetStructure Cache Appliance transparent interception works:

Step 1 The appliance intercepts client requests to origin servers. Several appliance deployment methods exist so that interception can take place. See Interception strategies‚ on page 121 for details.

Step 2 The Adaptive Redirection Module (ARM) redirects requests destined for origin servers to the appliance application. See ARM redirection‚ on page 125 for details.

Step 3 A very small number of clients and servers do not work correctly through proxies. The appliance identifies these problem clients and servers dynamically, and the ARM adaptively disables interception for these clients and servers, passing their traffic unimpeded to the original server. Also, clients and servers can be manually exempted from caching by configuring the ARM. See Adaptive interception bypass‚ on page 126 for more information.

Step 4 The appliance receives and begins processing the intercepted client requests as usual. If a request is a cache hit, the appliance serves the requested document or news article. If a request is a miss, the appliance retrieves the document from the origin server and serves it to the client.

Step 5 On the way back to the client, the ARM changes the source IP address to the origin server IP address and the source port to the origin server port.

Interception strategies

The transparency routing solutions supported by the Intel NetStructure Cache Appliance are:

Layer 4-aware switch. See Using a layer 4-aware switch to filter transparency requests‚ on page 122.

Cisco IOS-based router using the Web Cache Control Protocol (WCCP). See Using a WCCP-enabled router for transparency‚ on page 123.

Policy-based routing. See Using policy-based routing to filter transparency requests‚ on page 124.

How client request traffic reaches the appliance depends on network topology. In a complex network, you must decide which clients are to be served transparently and make sure that the appliance is positioned to intercept their requests. The

Appendix A Caching Solutions and Performance

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Intel 1520 manual Serving requests transparently, Interception strategies