WAN Optimization, LAN Degradation

A number of analyst firms and our own surveys indicate that there's a growing trend toward data center consolidation. The drivers are many--better data management and backup, regulatory requirements, cost reduction and better information security practices.

A complicating factor is remote office support. Backhauling fat apps across the WAN puts a great deal of stress on slow links for both bandwidth and latency-sensitive applications. One potential solution is WAN optimization, which makes more efficient use of your WAN.

Example products from vendors like Bluecoat, Cisco, Citrix and Silver Peak can significantly reduce WAN utilization while improving application performance on the LAN and for the end user. Claims of 10 percent to 40 percent increases are possible if the traffic is well-suited to optimization--repeating data.

One of the potential impacts of WAN optimization that you must plan for is the increase of LAN traffic in the data center and the remote office. Many IT shops scale their LAN based on applications crossing the WAN where bandwidth and latency are the limiting factor. Once WAN optimization isturned up, much of the bandwidth restrictions and latency is mitigated on the LAN side. The result is that LAN traffic spikes because, for example, a file server is now feeding a local appliance which is demanding far more traffic than a remote user did. In addition, more server resources are going to be consumed serving the additional demand. Granted, some WAN optimizers also cache files, which offsets the LAN server load, but you may still see marked increases.

When testing WAN optimization, be sure to also evaluate the impact of the LAN and servers and be sure to plan for it.