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WAN aggregation: Why you should consider this application delivery optimization technique

What is WAN aggregation, and how does it work? Our expert explains why all companies should consider this type of application delivery optimization.

In a technological landscape focused on business agility and lowered communications costs, WAN aggregation combines...

the strengths of cheap, consumer-grade Internet with dedicated WAN connections. It even allows some companies to get rid of their dedicated WAN connections entirely, without giving up the reliability and performance they need.

The enterprise continues to spread to more and smaller branches, and wants to put those branches into places with lower real-estate costs that are closer to staff or to market opportunities. This shift often makes traditional wired WAN connections from branch to data center harder to get and more expensive when available. Unavailability and expense drive many companies to explore using both consumer-grade Internet and wireless WAN connectivity (like 3G LTE and 4G LTE) for easy-turn-up/easy-turn-down connectivity.

How WAN aggregators work

Even when dedicated WAN links are replaced with plain Internet connectivity, the responsibility of optimally running virtual desktop infrastructure, IP telephony and other key services is still up to IT. Fortunately, WAN aggregation tools offer IT a way to make those applications run with adequate performance, prioritization and reliability. WAN aggregation appliances take multiple connections, whether WAN or Internet, and make them look like a single link with higher capacity and reliability than the individual links. Rather than providing for failover connectivity from one connection to another (a hot-cold strategy), they use all connections all the time (a hot-hot strategy). They are deployed symmetrically, with appliances in the branch talking to one or more appliances in the data center.

WAN aggregation tools offer IT a way to make applications run with adequate performance, prioritization and reliability.

Typically, WAN aggregators will also introduce some logic and intelligence into the mix, allowing network engineers to designate traffic priorities and application performance profiles that are to be delivered. For example, they can designate some traffic as critical, to be delivered first as long as packets are flowing, and other traffic as best-effort-only, to be dropped if available capacity drops. Some can set throughput floors (the least amount of bandwidth to be dedicated to an app) and ceilings (the maximum amount of bandwidth dedicated to an app) and other kinds of performance targets to handle performance issues like latency. These are traditionally functions of WAN optimizers, although aggregators typically do not bring the same broad range of traffic optimizations into play; for example, they generally won't do compression and protocol accelerations.

When combining a highly reliable WAN link that has higher costs per bit with a less-reliable Internet link that costs less, WAN aggregators leverage the strengths of each. They lean on the high-reliability link for critical traffic and use the cheap bandwidth to boost throughput for the overall load. When pairing multiple Internet links, assuming they come from different providers (and ideally along different paths), aggregators can optimize delivery based on current transit times through each provider's network.

Evaluating WAN aggregators

When evaluating WAN aggregators, ask your potential vendor these questions:

  • What are the number and capacity of the links your WAN aggregator can manage simultaneously?
  • What performance characteristics can your WAN aggregator manage?
  • How many classes of traffic can your WAN aggregator juggle, and can it automatically recognize and tag traffic from various applications as belonging to a given group?
  • Does your WAN aggregator add other optimizations to the mix, such as link multiplexing and split routing (sending outbound Internet traffic out across the Internet directly, instead of routing it through the pseudo WAN link back to the data center)?
  • How many branch appliances can talk to a single data center appliance?
  • How is high availability managed in branches and in the data center?

Any enterprise contemplating networking new branches or a refresh on existing connectivity should be examining the possibilities of nontraditional links -- wireless WAN and Internet -- and should include the option of WAN aggregation in their thinking, for some or all branches.

This was last published in November 2013

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