If you’re trying to decrease network traffic and streamline Internet access, Microsoft Proxy Server 2.0 might be the tool you need. It reduces the number of Internet connections made from the network by caching requested Web content, either on a single server or distributed across an array. Server hierarchies allow a central server or array to handle Internet connections, reducing security needs for lower-level servers.

Caching in
When a workstation user views Internet content, Proxy Server 2.0 caches that content on the server. If that user or any other user subsequently attempts to access the same Web site, Proxy Server sends the pages directly from the cache rather than making another connection across the Internet. The Web pages themselves control caching via a time-to-live value. When a cached site or page becomes outdated, the Proxy Server requests a new copy from the site. All client workstation traffic to the Internet passes through the Proxy Server, so the server can limit Internet traffic, making a connection only for un-cached content.

Obviously, Proxy Server’s caching reduces the amount of bandwidth used on the Internet connection. This streamlining effect becomes particularly important if multiple users are accessing the same Web site, such as in a classroom or training setting.

Proxy Server 2.0 engages in two types of caching: passive and active. When performing passive caching, Proxy Server stores Web pages a user has requested from the Internet. The Proxy Server cache—rather than a live Internet connection—then services subsequent attempts to access the same page. If a user tries to access the page after it has expired, the server initiates a new Internet connection to retrieve it.

Active caching is similar to passive caching in that it allows users to retrieve Web page information from the Proxy Server rather than from the Internet. However, active caching requires the Proxy Server to proactively download frequently retrieved sites. The server may retrieve new versions of expired pages even before a user requests them. In addition, an admin may configure the server to always cache certain sites. The server performs active caching after hours or when Internet activity is low.

Proxy Server arrays and hierarchies
Though caching helps eliminate problems related to slow Internet connections, bottlenecks may arise in two other areas: the Proxy Server itself and slow WAN links. Proxy Server eliminates these bottlenecks by using arrays and hierarchies.

Proxy Server allows the administrator to set up distributed caching among multiple Proxy Server-based computers. The admin can treat an array or group of Proxy Server-based computers as a single, logical entity. By acting as a single Proxy Server, rather than a set of individual machines, the array provides load balancing, fault tolerance, scalability, and ease of administration.

Proxy Server also enables caching across a hierarchical connection of individual Proxy Server-based computers or arrays. Client requests move upstream through the hierarchy until the requested object is located, reducing network traffic by moving caching closer to users.

Depending on the particular company’s environment, the admin may configure a Proxy Server to provide local caching of Web content in order to prevent excess Internet traffic on the WAN. As described earlier, when a workstation tries to connect to a Web site, it actually connects to the local Proxy Server. If the page is cached locally, the server returns the page to the client workstation without passing any information across the WAN or the Internet connection. Otherwise, the local Proxy Server passes the request to the central Proxy Server or Proxy Array, which can then fill the request from its own cache or request the information from the Internet. In this situation, remote Proxy Servers require less security than a central Proxy Server because they don’t access the Internet directly. In addition, each of the remote Proxy Servers needs only one network adapter.
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