NetCache documentation describes NetCache appliances in terms of the modes in which they can run, as determined by the protocols that they are configured to run. This section relates terminology sometimes used in the industry regarding proxy-cache servers to NetCache operation modes and describes those modes.
In the industry, proxy-cache servers are often identified as forward proxies and reverse proxies. Forward and reverse proxies are defined as follows:
From the client's perspective, a forward proxy operates on behalf of the client Web browser or media player. A forward proxy can handle requests for a virtually unlimited number of origin servers. Forward proxies are located close to the client.
A reverse proxy (also referred to as an accelerator) handles requests on behalf of the origin server, acting as an extension of the origin server. A reverse proxy, unlike a forward proxy, services one or a few origin servers. Random servers cannot be accessed through a reverse proxy server. Clients use the reverse proxy to access all origin servers that the reverse proxy is servicing.
A reverse proxy is usually operated by the same organization that operates the origin servers that the reverse proxy services. A reverse proxy is located close to the origin server.
The following table shows the modes in which NetCache appliances can run and how those modes relate to forward and reverse proxies as they are described in the industry.
A NetCache appliance that handles any or all of HTTP, FTP, Gopher, and Tunnel (for example, HTTPS and SSL) requests is referred to as a Web cache. Requests of these protocol types that would ordinarily have been sent directly to a Web server are sent to the Web cache instead.
See Chapter 4, Deploying NetCache as a Web Cache, for more information.
Network Appliance uses the term streaming media cache to describe a NetCache appliance that is configured to handle RTSP, MMS, or both types of streaming media. When NetCache is configured as a streaming media cache, streaming media requests (for example, audio and video) that would otherwise have been sent directly to a streaming media server are sent to the NetCache streaming media cache. A streaming media cache caches on-demand content (referred to video-on demand or VOD) and splits live media streams.
For live streaming media presentations, bandwidth savings are realized when multiple clients request the same unique stream. In this case, the streaming media cache makes a copy of a stream it is already delivering for each additional client that requests the same unique live media stream.
See Chapter 5, Deploying NetCache as a Streaming Media Cache, for more information.
When NetCache is configured as a Web accelerator (a reverse proxy for Web requests), it caches content from one or more Web servers that you identify, and provides that content to clients that request it. The Web accelerator is, therefore, an extension of the Web server.
Likewise, when NetCache is configured as a streaming accelerator, it caches streaming media on-demand content and proxies live streams from one or more streaming media servers that you identify, and provides that content to clients that request it. The streaming accelerator is, therefore, an extension of the streaming server.
See Chapter 6, Deploying NetCache as an Accelerator, for more information.
A NetCache appliance can be configured as a news cache to provide news caching service for news servers that support NNTP. A news cache requests news from a news server, on behalf of a client, delivers news content to clients, and caches news objects.
See Chapter 7, Deploying NetCache as a News Cache, for more information.
The NetCache Global Request Manager (GRM) feature uses DNS routing to direct content requests from clients in a Content Delivery Network (CDN) to the NetCache appliances that are closest to the clients.
See Chapter 11, Global Request Manager, for more information.
For deployments with heavy traffic loads, Network Appliance recommends that you configure the NetCache appliance for a single service, such as streaming media or Web service. Deploying dedicated NetCache appliances improves hit rates and bandwidth savings. Smaller deployments with lighter traffic loads, such as branch offices in an enterprise, might be able to run multiple services on a single NetCache appliance without affecting performance.
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Last updated: 11/13/02 18:10:50