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Web Caching / L4 Redirection Support on the Matrix N-Series


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Article ID: 7110

Products
Matrix N-Series DFE

Solution
Basic "Web Caching", also known as "Layer 4 Redirection", is not presently supported on the DFE.

However, support for an enhanced version of Web Caching known as "Transparent Web Cache Balancing" (TWCB) is supported with firmware 6.11.01.0040 and higher. Router 'ip twcb...' command set visibility also requires an Advanced Router license and a minimum of 256MB of memory on all modules in the chassis (5025).

Release notes state, in the 'New Feature Summary' section:
"Transparent Web Cache Balancing (TWCB) - provides for the storing of frequently accessed web objects on a cache of local servers. Each internet request (HTTP) request is transparently redirected by the Enterasys Matrix N-Series to a configured cache server. When a user first accesses a web page or object, that page or object is stored on a cache server. Each subsequent request for the page or object uses the cached content, avoiding the need to access the host web site via the internet connection."

Why Would I Use TWCB in My Network?

For most networks, web services are the primary consumer of network bandwidth. Web caching reduces network traffic and aides in optimizing bandwidth usage by localizing web traffic patterns, allowing content requests to be fulfilled locally. Localization increases speed and decreases latency in the network without the cost of additional bandwidth. Localization also improves access times to web sites for the consumer.

TWCB adds three important elements to standard web caching: transparency, load balancing, and scalability:
  • In standard web caching, the user must set the browser to cache web traffic. Because web caching is highly sensitive to user preference, users sometimes balk at this requirement, and the inability to control user behavior can be a problem for the network administrator. TWCB is said to be transparent to the user because web traffic is automatically rerouted, and the ability to configure caching is removed from the user and resides instead in the hands of the network administrator. With TWCB the user can not by-pass web caching once setup by the network administrator. On the other hand, the network administrator can add users for whom web caching is not desired to a host redirection list, denying these users access to TWCB functionality.
  • In standard web caching, a user-cache is configured and assigned to a single cache server. TWCB provides for load balancing across all cache servers of a given server farm that can be configured for heavy web-users using a predictor round-robin algorithm.
  • Scalability is provided by the ability to associate up to 128 cache servers with the web-cache. This scalability is further granulated by the ability to logically associate cache servers with up to 5 server farms.
For a more detailed explanation, please refer to 11074.
See also: 11945.

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