The ABCs of WAN optimization savings

WAN-optimization gear has evolved from one-trick point products – compression boxes, QoS appliances, TCP optimizers, caching devices – into equipment that performs all these functions and saves big money by moving traffic quicker across wide area links.

Expect more from WAN optimization than just optimization

Here is a review of how these WAN optimization controllers evolved with an eye toward understanding the various functions these appliances perform so businesses make better decisions about which is best for them.

WAN optimization technology makes more efficient use of wide area links to the point that businesses can actually reduce bandwidth or at least put off the need to buy more. Gartner says to expect the devices to pay for themselves within three years or don't buy them. 

The goal is to make applications work better across long links connecting offices with data centers, a result of server consolidation that pulled servers out of branch offices and centralized them. In many cases WAN optimization controllers were actually required to make server consolidation work because without it client-server interactions were intolerably slow.

While these devices can produce fantastic payback, they should always be tested first on each customer's network running each customer's typical traffic because vendor performance can vary greatly depending on network conditions and application mix.

Table stakes

There is a key set of features to make this acceleration happen. The basic element of WAN optimization is compression. It cuts the number of bits needed to transfer data, thereby reducing the time for data to cross the wire.

Another feature, TCP acceleration, improves response times by overriding TCP when it tries to throttle back the rate at which traffic is sent because it is mistaking latency for congestion. These devices, located at both ends of WAN connections, maximize the sending rates and also build TCP back up to full speed more quickly after it has dropped off.

Click to see: Chart of WAN optmization benefits

Still another element, file caching, stores frequently requested files on disks within the WAN optimization controllers themselves so when they are called for, they are delivered locally not over the WAN.

These all either reduce the number of bits that have to cross the connection or load the line with as much traffic as it can handle.

A final key feature is traffic shaping and prioritization, the goal of which is to make sure certain classes of traffic respond faster relative to others that are deemed less important. Traffic shaping sets limits on how much bandwidth certain traffic types can get and which ones are allowed to go first when there is contention. This can be done by enforcing the quality of service assigned to each class of traffic.

About five years ago, WAN acceleration vendors started buying each other up in order to compile these core technologies. For example, Cisco bought Actona for its file caching capabilities in 2004. Citrix bought Orbital Data in 2006 for its TCP acceleration. Juniper bought Perebit for its compression technology in 2005.