WAN acceleration gear grows up

Businesses should expect to face a wide and confusing array of choices when seeking the right WAN-acceleration gear to make transaction times tolerable as they shift from branch office servers to centralized server farms.

Centralization reduces the number of servers and so saves capital and maintenance costs, and improves security. But it also means more end users access data via the WAN - users who will scream if performance degrades as a result.

Availl, Cisco and Brocade offer products tuned to speed up specific types of WAN traffic - wide-area file services or WAFS - which represent a large chunk of the new WAN traffic that results when servers are centralized. But a throng of other vendors says its more broadly focused gear is better suited to real customer needs. All WAN traffic can benefit from acceleration, they say, and not all WAN traffic is WAFS.

This more broadly focused equipment can boost the performance of a range of network traffic, not just WAFS, although some vendors are tuning their gear so it gives special treatment to WAFS, as well. These WAN-acceleration vendors include Array Networks, Converged Access, Expand, Juniper, Orbital Data, Packeteer, Riverbed Technology, Silver Peak Systems, Swan Labs and others.

As an example of this tweaking for WAFS, Packeteer this week is announcing a software download for its PacketShaper appliances that can target priority treatment for Microsoft Windows Server 2003 R2, as well as Active Directory, Exchange and distributed component object model traffic. Packeteer also is teaming with Tacit Networks to provide a separate Tacit appliance that caches data in branch offices as a way to speed WAN transactions.

A crowded field

The WAN acceleration field is crowded because vendors have the opportunity to get a cut of the $5 billion spent this year on branch office infrastructure, and that number will rise next year, says Cindy Borovick, director of data center networks for IDC.

If the devices can help data center consolidation by boosting performance, they can pay for themselves over time, making them attractive to corporations, she says. But the variety of vendors and the varying mix of techniques they use mean customers have to do their homework to find the product that is best for them.

All the gear in question have certain things in common. For instance, they are generally deployed in pairs at either end of WAN connections, prioritizing and altering traffic to make it cross the links more efficiently.

Vendors are dealing with a common set of problems rooted in the fact that WAN bandwidth is less than LAN bandwidth, making response time slower for each traffic type as it waits its turn. As applications compete for this bandwidth, those that are less important to the business might disrupt more critical ones unless something is done about it.

Competition for bandwidth is compounded by network delay in cases where traffic crosses long distances and by the slowing effects TCP has when it throttles back transmission rates to make up for what it perceives as network congestion. The result can be applications that perform so poorly that end users complain, or worse, don't use the applications as they should for best productivity.

To handle these problems, vendors have an array of technologies, including compression, caching, prioritization, application enhancement and TCP acceleration. Not every vendor uses all of these and each might use a different mix. As a result, acceleration devices from one vendor might provide more improvement than devices from another even though they are placed on the same link and try to speed performance for the same traffic.

A difference of opinion

Vendors come at the problem from different angles and have varied strengths. A sampling:

  • Expand compresses and caches traffic, and is adding Microsoft Common Internet File System (CIFS) proxying via an alliance with DiskSites.

  • Orbital Data focuses on optimizing TCP so all TCP traffic flows better.

  • Riverbed caches files and is customizing its treatment of specific traffic types - notably CIFS and Microsoft SQL traffic - so they perform better as a way to support WAFS, with other applications on its road map.

  • Start-up Converged Access monitors and measures bandwidth use per application, then applies acceleration methods selectively per flow.

  • Swan caches large patterns of data, independent of files, to reduce the amount of traffic crossing the WAN.

This variety of approaches leaves customers responsible for figuring out which approach will treat their traffic best. Vendor claims vary, but in certain circumstances, they say they can improve performance 90% or more.

For example, software developer Baker Hill in Indianapolis had a dedicated T-1 to synchronize its production SQL servers with those at its back-up site that was getting clogged as the business grew, says Eric Beasley, senior network administrator for the firm. He was looking for a way to squeeze more onto the circuit short term to avoid buying a second T-1 before the contract on the disaster-recovery site ran out.

He found that start-up Silver Peak met the need, reducing download times for certain files from 6 minutes to 15 seconds as the devices cached traffic patterns. He says he plans to try the equipment on a new link between Indianapolis and Taiwan, which poses a different problem affecting performance: network latency.

"We have to support a connection halfway around the world, so we can't reduce latency," he says. But he plans to check the Silver Peak gear in practice to see how well it works to improve performance in the face of that latency.

Traffic compression

SITA, the IT provider to air transport businesses, uses Juniper WAN acceleration gear as part of a managed service that saves customers costs by reducing need for higher bandwidth links. But specific performance improvements are hard to predict.

"It's application-dependent in terms of traffic compression," says Brijdeep Sahi, SITA's vice president of marketing. For instance, traffic performance for Microsoft Exchange improves 40% to 50%, but can improve more than 90% for certain custom applications, he says.

But because acceleration varies depending on traffic type and the mix of traffic on any given link, SITA must test customers' actual traffic before telling them what improvement to expect, says Pierre-Yves Benain, head of product line integration for SITA. In some cases, SITA lets customers try the devices to see how well they work for them. And the provider recommends updating performance expectations over time as traffic mix changes.

"Applications evolve, so we recommend that customers follow up with us to reevaluate the efficiency of the technology after a couple of months," he says.

WAN optimization optionsWAN gear that tinkers with traffic so more can cross WAN connections with predictable performance employs a variety of methods, but no single method solves the problem.
MethodProsCons
Quality of ServiceImportant applications get first crack at network bandwidth.Doesn’t help performance of lower priority traffic.
TCP optimizationShortens restart times after congestion throttles back transmission speeds.Doesn’t help non-TCP traffic; doesn’t reduce traffic volume.
CompressionReduces the number of bits that have to cross the WAN, making it less congested.Not all traffic is compressible.
CachingStores large chunks of repeatedly accessed data locally so it need not cross the WAN each time it is needed.Depending on the type used, can cause versioning problems with files and can pose a security risk because data is stored on them in branch offices.
Application optimizationMakes chatty applications talk more efficiently to improve response time and reduce WAN traffic.In its early stages so not all applications can be optimized.

Learn more about this topic

Bringing LAN-like file delivery to WANs

08/08/05

Why WAFS could be critical to performance

07/11/05

Antidote for ‘chatty’ protocols: WAFS

08/03/05

Server consolidation: A proven method to stop spiraling IT costs

02/21/05

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Copyright © 2005 IDG Communications, Inc.

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