Last time we discussed some of the factors that impact application performance. Today, we are going to discuss some of the characteristics of the current crop of application acceleration products.

The first generation of products focused on the WAN-centric factors that impacted application optimization and featured technologies such as compression and QoS. Compression enables the WAN to perform as if it had received a one-time bandwidth upgrade. QoS is required in those situations where bandwidth is scarce and there are one or more delay sensitive, business-critical applications.

In many cases, the first generation of products offered significant value but they could not address some of the application-centric issues associated with server consolidation; i.e., running Microsoft's Common Internet File System (CIFS) over a WAN. In addition, these products are very tactical as they address performance problems on individual WAN links.

The second generation of products resolved some of the latency-specific issues that were not addressed in the first generation by emphasizing application acceleration and focusing on technologies such as caching and application proxies.

Caching is often beneficial, however it also has some significant limitations. For example, caches in branch offices can be out-of-synch with each other and with the data stored at the central site. Also, since caches are application-specific, the IT organization will have to implement and manage separate caches for each application. Finally, because a cache interfaces directly with clients, it is responsible for functionality such as handling authentication and authorization as well as file locking. Inserting this layer of intelligence into a network adds management and security complexity.

Next time, we will discuss the key characteristics of the next generation of application acceleration products.

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Jim Metzler is vice president of Ashton, Metzler & Associates.