WAN Optimization in a Virtualized Setting

Ensuring acceptable application delivery performance became a top-of-mind issue in recent years. IT found that it had to support delay-sensitive and/or chatty applications across the WAN, as well as large file transfers between headquarters and branch offices. One of the primary ways that IT groups responded to these performance challenges was by deploying WAN optimization controllers (WOCs), usually implemented as stand-alone hardware-based appliances at both ends of a WAN connection.

Now, with the growing adoption of virtualization, IT organizations are facing a new wave of emerging application-delivery challenges. For example, desktop virtualization will mean a dramatic increase in delay-sensitive WAN traffic. Server-side desktop virtualization, for example, creates many small transactions over the WAN, while client-side virtualization streams apps over the network to user devices, increasing the network load.

On the up side, virtualization is also enabling some significant new application-delivery solutions, such as virtual WOCs (vWOCs), which offer IT organizations a number of advantages.

VMs Pave Way for vWOCs

A vWOC is one form of a "virtual appliance," where software that provides specific functionality - in this case, WAN optimization capabilities - runs in a virtual machine (VM) on a virtualized hardware platform.

Most IT organizations have virtualized at least some of their data center servers, for example, and it is becoming increasingly common to implement disk-storage systems that have storage virtualization capabilities. As a result, an enterprise's data center usually already has VMs that can be used to host one or more vWOCs.

In a branch office, a suitably placed virtualized server could host a vWOC as well as other virtual appliances, forming what is sometimes referred to as a "branch office in a box," or BOB. Alternatively, a router such as Cisco's ISR G2 that supports router blades could also host a vWOC and function as a BOB. Virtual appliances can therefore support branch-office server consolidation strategies by allowing a single server, router or other device to perform multiple functions that once required several physical devices.

Another important factor driving vWOC deployment is the relative ease of transferring a vWOC between servers. For example, a major challenge in migrating a VM across physical servers is replicating the VM's networking environment in its new location. By virtualizing WAN optimization services, however, it's possible for both server VM workloads and associated vWOC networking services to automatically move together from device to device across the network to wherever adequate resources are available.

In addition, many IT organizations choose to implement a proof-of-concept (POC) trial prior to acquiring WOCs. Such a trial lets IT quantify the performance improvements provided by the WOCs and understand related issues such as their manageability and transparency. While it is possible to conduct a POC using a hardware-based WOC, it is easier to do so with a vWOC, which can be downloaded in a matter of minutes. By contrast, a physical device takes days to be shipped, installed and tested.

Time differences can be even more acute if the WOC is being deployed in a part of the world where it can take weeks or months to get a hardware product through customs. Another reason it is easier to conduct a POC with a vWOC is that some vendors let users download a vWOC without any vendor contact; others provide a version of their product that is completely free and obtained on a self-service basis.

Swan Song for Physical Appliances?

Virtualization is fundamentally changing the IT function, both by creating new performance challenges and by enabling new solutions that help IT organizations respond to them. However, organizations that are evaluating vWOCs need to assess them from a variety of perspectives, including the functionality they provide, their performance, the pricing model and the overall strength of the vendor.