Caching 101: Adding Content Control

Many cache appliances make it easy to add an attractive feature to your Internet access service offerings: content control through site filtering

by Amit Pandey
Director of NetCache, Network Appliance, Inc.

The demand for ISPs to offer Web content filtering is growing dramatically. Filtering has evolved as an efficient way for ISPs to do several things:

•  help consumers to steer clear of inappropriate Web content
•  provide safe and productive Internet access to schools and libraries
•  reduce the legal liability associated with questionable Web content  provided for corporations
•  maximize employee productivity by reducing non-productive Web "surfing" for corporations using their service.

This Caching 101 installment explores how caching can provide an easily deployable, high-performance filtering solution for ISPs.

Q: What is the relationship between caching and filtering?

A: Filtering of Web traffic involves examining all Web requests. Caching of Web traffic involves handling all Web requests. It is therefore natural to combine filtering with caching.

Q: What are the benefits of combining filtering and caching?

A: By integrating Internet filtering software with a Web cache, ISPs get a more deployable filtering solution that's easy for their end users to customize -along with the performance improvements associated with caching. Standalone filtering solutions may slow user response times, and requires additional investment in hardware and software.

Q: How does filtering work?

A: There are two types of filtering technologies - filter lists and software algorithms. Lists contain URL and IP addresses that are to be blocked. The lists are updated regularly and are examined by people to ensure correct categorization. Algorithms use heuristics to determine if the page should be blocked, and therefore have higher error rate than filter lists.

Q: How would an ISP integrate an Internet filtering solution with a cache?

A: Internet filtering tools are most widely available as network software, though client software is also available. For ISPs, network software utilizing filter lists is the simplest, most accurate, and most manageable solution, as it only needs to be deployed at the data center. Client software needs to reside on all clients' systems.

Companies like Secure Computing and N2H2 make filtering tools that let ISPs configure and manage Internet Web access policies for both individual customers and corporations. Most filtering solutions are designed to integrate with caches; for example, the Network Appliance NetCache™ appliance has Secure's SmartFilter™ tool built right into the cache, making filtering very easy for ISPs to deploy and administer--while being completely transparent to end users.

Q: Are there any additional benefits in combining caching and filtering?

A: Yes: Caches automatically log all Internet traffic, which allows administrators to review logs and thus take appropriate actions depending on filtering parameters. Further, most caches allow an ISPs' customers to apply their own filter lists, if their access needs are different from the standard categories provided through a third party's filtering application.

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