What slows down app performance over WANs?

* Elements that affect app performance

In the past year, we have written multiple newsletters on the topic of application acceleration (see below for some examples). We have devoted so many newsletters to this topic for several reasons. First, the topic area is of growing importance to many IT organizations. Second, it is a confusing area because it is comprised of many different techniques that are all intended to optimize one part of the overall challenge of application acceleration. Third, we are going through a time of consolidation and expansion on the part of the vendors as large established players acquire smaller companies at the same time that new companies enter the market.

In addition to being an important topic, application optimization is also extremely complex. In a recently published article Jim outlines some of the challenges associated with application optimization. Some of these challenges exist within the WAN, while others are caused by the application itself.

One of the WAN centric features that impacts application performance is the TCP windowing algorithm.The TCP window size indicates how much data can be outstanding without an acknowledgement. A technique called window scaling, based on RFC 1323, allows IT organizations to increase the TCP window size.

One of the application centric features that impact application performance is the use of chatty protocols such as CIFS (Common Internet File System) or NFS (Network File System). Feeling the effect of these protocols are companies that have centralized their Microsoft file servers and that are not yet running R2, the new Windows Server release.

Another application centric feature that impacts application performance is the application blueprint - the way that the application structures transactions, including the type and volume of data that must be transferred between and among devices.

In the next WAN newsletter, we will describe some of the application centric factors that impact application performance.

* Examples of recent application acceleration newsletters: Automating application acceleration; QoS, visibility and reporting are hot optimization techniques, users say; WAFS could answer CIFS' limitations.

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