Need for speed

WAN optimisation has become a crucial consideration for IT managers in the struggle to improve application delivery across distributed offices. Barry Mansfield unearths some of the important criteria that IT managers should keep in mind when making the investment.

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By  Sathya Ashok Published  August 15, 2007

WAN optimisation has become a crucial consideration for IT managers in the struggle to improve application delivery across distributed offices. Barry Mansfield unearths some of the important criteria that IT managers should keep in mind when making the investment.

How do I know if my company's existing network might need a WAN optimisation solution?

If you know that your company needs to adopt WAN optimisation technology then it is probably already too late, because your clients are likely to be complaining already that they are observing poor performance.

"If there are no actual problems you want to be sure that it stays that way," says Werner Heeren, regional sales manager for EMEA at Fluke Networks.

"By monitoring the various links you will know whether WAN optimisation is needed, before you are informed by your users. Most CIOs think that the WAN is the bottleneck for slowness. When users are complaining about a slow network, the manager should investigate the cause. Is it really the network or the WAN or is it maybe the server farm, or the application? How do you know? By measuring the total application response time."

NME recommends: If your company is expanding its branch network or consolidating its servers, now is a good time to check application responsiveness so that you can start problem shooting at an early stage.

How do I justify investing in WAN solutions to my management?

"The typical multinational will want to extend its core applications from the headquarters to the branch, as if the user is sitting in the headquarters," says Cherif Sleiman, chief technologist for MEA at Cisco. "Imagine that 70% of your employees are in branches. The IT experience you offer these people directly affects their performance. You are paying them salaries, bonuses and providing healthcare, so you want to make sure they are ultimately productive."

Fluke Networks' Heeren recommends drawing up a report that reflects the influence of the round trip time over the WAN compared to the total application response time. "Or you could go further by assuring an SLA (Service Level Agreement). This way you can guarantee a specific response time for an application. If this cannot be met, then necessary counter measures can be taken."

NME recommends: Building in appropriate checks and balances, so that all eventualities are covered, should convince an organisation's senior management that the investment in WAN optimisation is sound.

What can these solutions actually do to improve network and application performance?

Optimisation techniques for WANs can improve most organisations' response times and save them from having to invest in costly bandwidth upgrades, particularly when branch office servers are being centralised. Some examples of performance improvements include accelerating CIFS performance, by predicting client requests, and pre-staging data to the client. This greatly improves performance for Windows file transfers, directory browsing, and remote access to Microsoft applications such as MS Word, Powerpoint and Excel.

TCP throughput is known to degrade significantly on high-latency, intercontinental links. "Bandwidth is often touted as the answer to application performance problems, but because of the way TCP protocol works, adding bandwidth is often ineffective," points out Sudhir Sanil, technical manager for the ME at F5 Networks.

NME recommends: Be assured that WAN optimisation technologies are proven and cost effective, though some are better than others. An optimisation solution can employ adaptive TCP optimisation, enabling adaptation in real time to the latency, packet loss and congestion characteristics of WAN links, accelerating virtually all application traffic.

How do I know which solutions to pick with such an array of options available (real time reporting, network capacity planning, QoS, application performance monitoring and so on)?

It is advisable to start with real time reporting to ensure your WAN is free of problems. If not, it will help you to identify the reason for the same.

There are deployments that have no centralised management. This can defeat the object of WAN optimisation, because dedicated personnel are then required at the branch site to physically manage that solution. According to Cisco's Sleiman, integration is also a headache for IT managers and the ideal for WAN optimisation is that it becomes just another service that you turn on.

NME recommends:
All these features should be core. With multimedia becoming mainstream in every organisation, QoS (quality of service) is a must. Centralised management is also key - companies may have different needs, but you should strive to make life simple for employees in the branch office.

Is there a security compromise with any of these WAN optimisation solutions?

Only network-transparent products interoperate with other networking products such as firewalls, monitoring, and QoS devices. Many WAN optimisation controllers (WOCs) create TCP or UDP tunnels, meaning that all application traffic is multiplexed over a single TCP or UDP port between WOCs - and the addresses of packets flowing between WOCs are replaced with the addresses of the WOCs themselves.

These proprietary traffic streams are not understood by any device operating at Layer 4 and above. As a result, firewalls, monitoring and QoS devices will fail to work. Tunnelling also creates a static routing overlay, meaning that dynamic changes in routing tables can lead to unpredictable behaviour and even a complete loss of connectivity sometimes.

NME recommends: In large enterprise networks, with datacentres connected by dozens of distinct WAN links running dynamic, asymmetric routing and sophisticated network monitoring, QoS and security, it is essential that you have full visibility of your traffic. Look into the vendor's transparency claims before signing the final purchase order.

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