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What’s with WAN optimisation?

Dealing with latent tendencies

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The data centre is no longer alone. It's not a facility that occasionally releases data sporadically, on special occasions for particular jobs. As IT functions become increasingly centralised within the data centre, it's hammered constantly for both input and output by all parts of the business.

This has huge ramifications for the data centre's network connections. Centralising IT into a data centre is surely the smart thing to do, as it enables better, more fine-grained control and management of assets. The big question however is if the network can handle all the extra traffic that's being generated.

If you're part of a large organisation with offices scattered around the country, or around the globe, your users will be accessing their data not from a machine in the local server closet, but from a virtual server, third row down on rack H22.

But when that happens, do users still feel that the data is being accessed locally? The answer had better be yes, or the helpdesk's phone lines will be glowing.

Bandwidth or Band-Aid?

If the answer is no, as it's likely to be, the answer may be to throw more bandwidth at the problem. For some, that works as long as the data isn't too far away, and the transit time between facility and user isn't too critical.

Slight delays might be OK for accessing a word-processed document, but won't be fast enough for a database accessing multiple data sets to compile the results of a query, or for streaming video or supporting a VoIP call. Delays in such situations quickly prove unacceptable.

Consider too the impact on essential functions such as backup and disaster recovery. Here we're talking about very large volumes of data that need to be pumped across a wide area link. The faster it goes, the shorter the backup window.

For some of these circumstances, buying more bandwidth can solve the problem. It might keep the backup window manageable for now, although average annual data growth rates of 50 per cent don't suggest that this is a viable long-term strategy.

Latent variables

An alternative is to consider WAN optimisation. In essence, this technology involves parking a box at either end of the WAN link, hooking the network through them, and letting them manage the connection.

All WAN optimisation systems use a variety of techniques to minimise WAN traffic and minimise the effect of latency - the time delay created by the finite speed of light.

To do this, they tweak the network's parameters to provide the best throughput for the link's speed, they compress and deduplicate data at the block level, so effectively increasing the bandwidth available.

They also use cacheing, which is by far and away the most effective of the techniques, as it avoids a file traversing the WAN link more than once.

The network parameters tweaked usually involve reducing the network protocol overhead by performing such adjustments as increasing packet size, which cuts the number of packets crossing the link.

Chatty WAN

Application awareness can also speed WAN traffic, and therefore the business. WAN traffic typically includes email and web browsing, Windows file shares, rich media, external and business-critical applications, and real-time applications, such as video-conferencing. Many of these applications can be chatty, as they were not originally designed to run over a WAN.

WAN optimisation technology can manage such traffic by prioritising real time applications, such as VoIP, ensuring that one individual's file transfer doesn't cause drop-outs on someone else's conference call. They can also ensure that protocols such as CIFS and MAPI are optimised for WAN use, so that only the traffic that needs to traverse the link actually does so.

And since the WAN optimiser understands the traffic flows, it can add security to your network. Some vendors offer the ability to block undesirable data types, depending on policy. You could block in appropriate web surfing, peer-to-peer traffic, YouTube, and so on.

So if you are managing a data centre, connectivity is key. There are other means for gaining some of the benefits of WAN optimisation, such as deduplication and cacheing, but it remains the only way to get the benefit of all of them in a single box -- which in itself offers its own payback.

All you have to do now is the cost-benefit analysis. ®

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