Network Caching

Network Caching

Network caching is the technique of keeping frequently accessed information in a location close to the requester. A Web cache stores Web pages and content on a storage device that is physically or logically closer to the user–closer and faster than a Web lookup. By reducing the amount of traffic on WAN links and on overburdened Web servers, caching provides significant benefits to ISPs, enterprise networks, and end users.

There are two key benefits:

• Cost savings due to WAN bandwidth reduction–ISPs can place cache engines at strategic points on their networks to improve response times and lower the bandwidth demand on their backbones. ISPs can station cache engines at strategic WAN access points to serve Web requests from a local disk rather than from distant or overrun Web servers.

In enterprise networks, the dramatic reduction in bandwidth usage due to Web caching allows a lower-bandwidth (lower-cost)WAN link to serve the same user base. Alternatively, the organization can add users or add more services that use the freed bandwidth on the existing WAN link.

Improved productivity for end users—The response of a local Web cache is often three times faster than the download time for the same content over the WAN. End users see dramatic improvements in response times, and the implementation is completely transparent to them.

Other benefits include:

• Secure access control and monitoring—The cache engine provides network administrators with a simple, secure method to enforce a site-wide access policy through URL filtering.

• Operational logging—Network administrators can learn which URLs receive hits, how many requests per second the cache is serving, what percentage of URLs are served from the cache, and other related operational statistics.

How Web Caching Works

Web caching works as follows:

1. A user accesses a Web page.

2. The network analyzes the request, and based on certain parameters, transparently redirects it to a local network cache.

3. If the cache does not have theWeb page, it will make its ownWeb request to the originalWeb server.

4. The original Web server delivers the content to the cache, which delivers the content to the client while saving the content in its local storage. That content is now cached.

5. Later, another user requests the same Web page, and the network analyzes this request, and based on certain parameters, transparently redirects it to the local network cache.

Instead of sending the request over the Internet and Intranet, the network cache locally fulfills the request. This process accelerates the delivery of content.

The important task of ensuring that data is up-to-date is addressed in a variety of ways, depending on the design of the system.

The Benefits of Localizing Traffic Patterns

Implementing caching technology localizes traffic patterns and addresses network traffic overload problems in the following ways:

• Content is delivered to users at accelerated rates.

• WAN bandwidth usage is optimized.

• Administrators can more easily monitor traffic.