Vista via WAN not an optimisation cure-all

The new OS offers improvements on previous Windows versions, but won't solve all woes

Windows Vista has users buzzing about network performance improvements, but industry watchers caution that the new operating system is no WAN-optimisation panacea.

In certain scenarios, the improvements implemented in Vista and slated for Windows Server 2008 (Longhorn), will alleviate the problems of latency and inefficient protocols that have hampered application performance over the WAN. But the improvements will have little or no effect on performance until PC hardware is upgraded, applications are reworked and Microsoft Vista or Longhorn machines sit at both ends of a WAN link.

From a communications perspective, Longhorn and Vista are works in progress, says Joe Skorupa, a Gartner research vice president. “There’s a lot to like, but don’t dash to deploy Vista just to get these features. As well-tested as it has been, you’ll want to make sure you take a measured approach to deployment.”

For the most part, Vista’s performance gains are directed at file-sharing over WANs, which has become an important new datacentre issue for organisations as the number of employees working in remote offices climbs. Most significantly, Vista features a rewritten TCP/IP stack and improvements to Common Internet File System (CIFS), the native Windows access protocol that enables file- and print-sharing among devices.

For the new TCP/IP stack, Microsoft changed its congestion-control algorithms so more data is sent at higher speeds. “It does some autotuning things, and it takes advantage of large window sizes — stuff the research has been pointing to for a while that will make TCP run a lot better in high-bandwidth, high-latency environments,” Skorupa says.

Microsoft based its Vista implementation of CFIS on a new version of the Server Message Block (SMB) protocol that lets multiple data blocks be sent over the WAN simultaneously, instead of requiring that blocks be sent individually and waiting for acknowledgment that each has been received.

These CIFS and TCP improvements will have the most positive impact on long file-transfers, such as large media files that have been compressed as much as they can be, says Eric Siegel, a senior analyst at research firm Burton Group. But don’t count on Vista to do data reduction-based compression as dedicated WAN-optimisation appliances can, he says. Nor will Vista’s performance enhancements have much effect on web-based applications, Skorupa adds.

“They’re not going to take a badly structured, browser-based app that does 70 round trips on the network to paint a screen down to five round trips,” he says.

Another consideration is that companies won’t benefit fully from the TCP and CIFS enhancements unless they have Longhorn or Vista machines on both ends of a link.

Further complicating the CIFS issue is that a number of third-party and homegrown applications, because they were developed specifically for the LAN, never took advantage of some of the advanced features in SMB 1.0. Getting these applications to take advantage of the improvements in SMB 2.0, on which the Vista CIFS implementation is based, is not an attractive prospect for many IT departments, Skorupa says. Deploying WAN-optimisation gear is much quicker and far less painful than restructuring an application, he says.

Another performance feature Microsoft has focused on in Vista is QoS, incorporating management tools that let administrators link application policies to user profiles via Active Directory. Using Active Directory information about employees’ and groups’ access rights as the base, administrators can potentially make decisions as fine-grained as giving a particular finance employee high-priority access to SAP applications during the last two weeks of a quarter.

On the whole, Microsoft has made great strides to improve application performance over the WAN, but Vista’s enhancements are not going to wipe out the market for specialised WAN-optimisation gear any time soon. “There’s a lot of cleanup here, and it took Microsoft a long time to do it. But that said, it’s good stuff,” Skorupa says.

Taking advantage of all the good stuff will require hardware upgrades. Most existing desktop machines lack the processing power, memory and graphics capabilities to take advantage of Vista, Skorupa says. “This is not a no-cost upgrade.”

Significant software testing is required, too. “Enterprises have hundreds, and in some cases thousands, of in-house applications that they have to test,” Skorupa says.

That’s a serious consideration for Hyundai Information Services North America. David Jung, technical lead for infrastructure engineering security at the automaker’s IT unit, is running Vista on his work PC, but says Hyundai has no immediate plans to implement it company-wide. The appeal of performance enhancements is outweighed by the daunting reality of how a client operating-system upgrade could break dozens of existing applications, Jung says.

“One of the big issues is that we need to verify all the applications will keep working on Vista. It will take some time,” he says. In addition, he says, the CPU and memory required to run Vista is a factor for waiting.

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