Learning about ICAP

What is ICAP?

ICAP is an open-ended protocol that is designed for easy extensibility of the capabilities of a proxy-cache server and offloading of specific Internet-based content to dedicated servers for adaptation of that content.

The NetCache ICAP feature works in conjunction with ICAP servers running ICAP applications to provide content adaptation services. When configured for ICAP service, a NetCache appliance directs content, or requests for content, to an ICAP server that can provide the necessary content adaptation service. The ICAP server then executes the service and responds to the NetCache appliance with the adapted content or request.

Examples of ICAP services

ICAP is an emerging technology that supports flexible and diverse services for content adaptation. Network Appliance is collaborating with vendors on an ongoing basis as they add ICAP services.

Examples of current ICAP services are described in the following paragraphs.

Virus scanning

Historically, the receiving network or computer has often been responsible for virus scanning, which can result in the same object being scanned multiple times. With ICAP virus scanning, the scanning takes place before the object is passed to the client.

For example, if an ICAP virus scanning service is deployed and a user requests an .exe (executable) file, NetCache passes the .exe file returned by the origin server to an ICAP server. The ICAP server checks the .exe file for viruses and removes any viruses it finds or denies the user access. After the ICAP server performs its service, it returns the (possibly modified) content to the NetCache appliance for caching and delivery to the client.

Content filtering

Content filtering provides the ability to check requests to determine if the type of content requested is authorized.

Historically, content filtering has been performed by a proxy-cache server based on information the administrator manually configured or based on content filtering database files downloaded to the proxy-cache server, for example, SmartFilter or WebWasher DynaBLocator.

ICAP content filtering applications expand your choices for what to use for content filtering. You can easily switch ICAP content filtering applications later, if you find a better solution after deploying your proxy-cache server and ICAP server.

Unique to ICAP is that ICAP content filtering can work in conjunction with other ICAP services. For example, you can feed the results of content categorization returned by an ICAP content filter into an ad insertion ICAP service so that only the pages appropriate for ad insertion are sent to the ad insertion service.

Translation of Web pages, images, streaming media for presentation on cell phones and other wireless devices

Historically, content has been statically converted and has resided on origin servers. Or, gateways have been deployed to translate a particular device's language to a format appropriate for the device.

With ICAP service for wireless markup language, when a Web cache receives a request from a cell phone browser, the cache delivers the requested content to an ICAP server that adapts the content for display on the cell phone. The Web cache then serves the page and caches it for subsequent cell phone browsers.

Language translation

Historically, content has been statically converted from one language to another, for example, from English to French, and has resided on the origin server. Or, conversion has required resource-intensive APIs to be running on client computers or Web servers.

With an ICAP language translation service, if the content is not in the appropriate language for the requesting client, the NetCache appliance can send the content to the ICAP server for translation and then cache it and serve it to the client. The next client that requests the same content in the same language is served from the cache.

Advertisement insertion

Historically, advertisements have been inserted into Web pages based on the origin Web site's ISP, the hosting provider, or agreements with a Web site for purchasing direct advertisements.

With ICAP advertisement insertion, advertisements can be inserted into Web pages or new Web pages can be generated, based on customer preferences, location, or history, when the customer performs a request from a Web site.

Information about new ICAP services are provided at http://www.i-cap.org and http://www.netapp.com.

Benefits of ICAP

Value-added services through ICAP provides the following benefits:

ICAP is an open protocol. Any server or application provider can develop ICAP services. New applications are being developed on an ongoing basis.
Access to the Web servers is faster because resource-intensive services are off-loaded to servers dedicated to content adaptation.
Implementation with ICAP is scalable, supporting 100 to 100,000 desktops.
Many services can be supported without deploying chains of proxy-cache servers, which can affect performance.
Overhead and management to add additional services is low.

Possible issues for ICAP

Possible issues for ICAP are as follows:

Adding ICAP services to your network might increase network traffic, as described in Considering network traffic when determining ICAP services. Therefore, you need to weigh the benefits of providing ICAP services against the impact on network performance.
Increased latency might occur as a result of trips on the network to and from the ICAP servers.

Version supported

NetCache supports ICAP version 1.0.