Network World — Data center centralization and consolidation. Cloud computing. Latency-sensitive (real-time and interactive) applications such as VoIP, videoconferencing and virtual desktop infrastructures (VDI). Business continuity and disaster recovery. These enterprise trends are among those driving the need for a WAN access layer that is scalable, reliable and cost-effective.

While MPLS services from service providers such as AT&T, Verizon (VZ) and BT (BT) meet the "four nines" (99.99%) reliability requirements enterprises expect, they are extremely expensive. At typical U.S. domestic pricing of ~$400 per megabit per month for copper T1-based connections for the typical remote office, companies have simply been unable to scale bandwidth at anywhere near the rate at which demand is growing.

WAN optimization tools offer a way to delay bandwidth upgrades, and can perform wonders for application acceleration, but you can only put off the need for additional bandwidth for so long, especially as multimedia file sizes continue to increase and bandwidth-hogging applications like video become ever more popular.

Public Internet bandwidth is significantly less costly -- typically $10-$15 per megabit per month for ADSL, sub $4 per megabit per month for cable, and as low as $5 per megabit per month for high-speed bandwidth at carrier-neutral colocation facilities -- but these services are only about 99% reliability.

This is simply not reliable enough for most corporate WAN requirements. The popular perception of the Internet is indeed accurate: Unaided, the Internet works pretty well most of the time. But "pretty well" is not good enough for most enterprises, and "most of the time" is not good enough for almost any. Note that when we refer to reliability here, we mean the union of simple availability with whether packets are getting through to their destination without being lost or excessively delayed.

However, if one remembers their basic systems' reliability course lesson, while components which are each 99% reliable run in series deliver only 98% system reliability, the same components run in parallel, in a properly designed system, will deliver 99.99% reliability.

A new technology called WAN Virtualization combines diverse IP WAN circuits at each location, and makes it possible to get 30 to 100 times the bandwidth per dollar, 40% to 90% WAN cost savings, and more reliability and application performance predictability than the best, single-vendor MPLS network.

Where server virtualization leverages the efficient pooling of computing and storage resources, WAN Virtualization does a similar pooling of wide area network resources. An appliance-based WAN Virtualization solution typically wraps a layer of hardware and intelligent software around multiple WAN connections -- existing private links such as MPLS, as well as any kind of Internet WAN link, be it DSL, cable, fiber, Metro Ethernet, etc. -- to augment or replace private WAN connections, delivering not only more bandwidth and lower monthly cost, but greater reliability and application performance predictability.

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