roxy caching isn't new, but what is new is the caching in Novell's Proxy Cache Server software, which is part of its BorderManager suite of InternetWare server products coming this fall. Although the Proxy Cache Server is just one component of BorderManager, it may help quiet all those users demanding faster computers to improve their Web access.

Looking for dramatic improvements in Internet performance, Novell bypassed the caching algorithms from CERN (the Geneva-based research organization) and instead adapted a combination of Harvest and Squid algorithms-developed through the Department of Defense's Advanced Research Projects Agency (ARPA).

Novell's cache servers communicate their contents to each other using the ICPv2 (Internet Cache Protocol version 2), which also grew from the Harvest and Squid research and is being proposed to the Internet Engineering Task Force. ICP is a lightweight message format used to communicate which URLs are in neighbor caches so Web objects can be retrieved from the most appropriate cache location.

Although ARPA funding for the Harvest Information Discovery and Access System ended last August, Harvest lives on through the work of loyal supporters. For example, other Harvest adherents include Netscape Communications' Catalog Server Internet search engine and the @Home Network cable-based Internet-access service. NetCache is a commercial Harvest product available from Network Appliance Inc. in Santa Clara, Calif.

Squid research grew out of the Harvest project. Unlike traditional caching software, Squid handles multiple requests for Web objects in a single, nonblocking process. An interesting aspect of Squid is "negative caching." Using ICP, Squid cache servers can be set into a mesh or hierarchical arrangement. When a Web server is down, the cache server sends a "negative" cache back to any requester to indicate that the source Web server is unavailable.

Another Squid feature that should resonate with Ne tWare fans is Domain Name Server caching-a natural extension to Novell's caching of directory information. The database running all NetWare security, Novell Directory Services (NDS), is a distributed system across the servers in mesh arrangements.

Decisions Last Year
Novell found these proxy cache technologies only about a year ago. Harvest and Squid were unfinished projects, with no ICP defined and no restrictions on use and licensing. Novell decided to rewrite the code to take advantage of the NetWare operating system, using kernel extensions for speed.

A superset of then-available caching code from CERN, Harvest-Squid technology was implemented as request blocks and work queues in NetWare rather than as threads in Unix.

Novell's unique HTTP Accelerator acts as a front end to multiple Web servers, caching commonly downloaded items such as icons, backgrounds, and graphics.

One bene fit of the Proxy Cache Servers is increased corporate security, since the servers can connect through the firewall to reach the Web servers, while hiding the real Web servers' Internet Protocol addresses from outsiders. Further, running the cache controls through NDS makes the Access Control List available to all cache servers. Attempts to connect to unauthorized sites can be blocked at the user's local cache server.

In the chart, a distributed corporate network connects local cache servers to one another and to hierarchical servers one level up. By leveraging fast links between parent servers, a cache user in Austin, Texas, can retrieve a Web object from Houston, Dallas, or even New York faster than from the original Web site. This allows companies to put high-speed (and high-dollar) links to the Internet at proxy cache hub sites, serving smaller sites connected with slower links.

Novell's Wolf Mountain clustering also gets a boost, as several Proxy Cache Servers can load-balance requests to internal Web servers.

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