Microsoft recently submitted its Cache Array Routing Protocol (CARP) to the Internet Engineering Task Force (IETF) as an Internet draft. CARP 1.0, implemented in Microsoft's Proxy Server 2.0, will let the browser use a hash-based routing method to determine which array member of a cache array to contact to locate cached data across the array. Instead of contacting a proxy server and then being forwarded to th e proper server that contains the cache, the client will automatically determine where to go.

The Microsoft and Netscape proxy servers that we tested also included a method for batch-updating the cache. The proxy administrator can create a schedule to download certain sites. In the lab, this method gave us a fresh copy of the sites we most frequently used without our having to refresh the cache. With Netscape's server, we adjusted the depth of hyperlinks to fetch into cache. This feature is useful for the administrator who fuels the server for periods of intense access. For example, a financial institution may batch The Wall Street Journal before the workforce arrives in the morning.

Cache replication may become more important to network administrators who are saddled with the task of freeing up band width by reducing excessive network utilization caused by some of the new push technology offerings, including PointCast Network, Netscape Navigator and Microsoft Internet Explorer. By updating the cache from the push sources on a scheduled basis, the pushed data is placed closer to the user, cutting down on high utilization of slow links.

Proxy servers can go beyond caching pages as they are encountered by selectively caching the most commonly transferred data. Although at first glance this may seem like a needless task, the truth is, administrators often have to wade through long, cryptic logs and schedule batch updates to keep the cache fresh and to determine where repeat traffic is coming from. Microsoft includes a feature in its proxy server, called intelligent caching, that identifies which cache to keep by using hit rates mixed with time shifts, or specific periods of peak load on a server. The proxy server then caches specific sites on a regular basis.

Bringing Home the Bacon Many small organizations rely on ISDN or analog modems for LAN-to-LAN routing. By selectively creating and tearing down the con nection through dial-on-demand, a proxy server creates a new connection only when the requested content does not exist in cache. We appreciated this tight integration when we tested Microsoft's Proxy Server's AutoDial feature. This feature works with Windows NT's RAS (Remote Access Service) to act as the agent for the LAN-to-LAN routing through modems connected to the NT server.

With such a strong emphasis on serving the small office, you'll find that a proxy server quickly pays for itself. In addition, small environments that rely on slow links, such as a 33.6-Kbps modem or a 128-Kbps ISDN connection, no longer have to suffer painfully slow transfer times, especially with simultaneous, multiuser access. We tested a file transfer over a slow link to see how quickly the second transfer (after the file was stored in the cache) would compare. The initial FTP took 234 seconds to retrieve, while the subsequent request took only 3.44 seconds. By simply adjusting the cache's time-to-live and running batch updat es on non-peak hours, small environments can maximize the use of their slow link.