Sometimes it’s surprising just how much cumulative savings can be gained through small actions. For example, if we all used one less gallon of gasoline a week, we’d reduce our oil imports by millions of barrels a year. The same is true with bandwidth usage. If your company can use just a little less WAN bandwidth each time an application is launched or a document downloaded, it can make a huge difference both in performance and in forestalling the need to lease additional circuits.
One of the ways to do that is through caching. The more you can hold documents, files, and applications locally, the less you have to chew up bandwidth going across the WAN to pull them each time your site’s employees need them.
Caching is one of the key elements in Sprint’s WAN Acceleration solution, provided by Blue Coat Systems. There are essentially three categories when it comes to caching – Cold (not yet cached), warm, and hot. Cold documents or applications have to be pulled across the WAN when they’re demanded, with the idea of caching them after the first request. Obviously, this initial request consumes the greatest bandwidth. But once documents or applications are in the local server, they can be held there on a warm or hot basis for further use.
With warm caching, after a user requests a document or application, the local proxy/cache server responds with the locally held version but checks across the WAN for any updates before delivering it to the user. Hot caching is the most efficient, particularly for frequently accessed materials. Thanks to a continual refresh algorithm, it ensures that the cached object is continually updated so when the request is made, the user does not have to wait for the update.
How much bandwidth can be kept off the WAN by caching is totally dependent on the type of work done by each office on the network. But you can do the math with file and application sizes to see how caching helps reduce overall WAN bandwidth. Cleaner WAN pipes mean better performance for everyone, as well as cost savings, since it reduces the need to add circuits.