How to improve WAN performance

How to tune WANs for better performance

The performance of applications across the WAN are beset by a range of problems – latency, congestion, chatty applications, contention with other apps, low bandwidth – that can be addressed in a variety of ways.

Users find the secrets of WAN optimization

Here are some tips from Gartner analyst Joe Skorupa on how to analyze the problems and speed up application performance over the WAN.

The performance of applications across the WAN are beset by a range of problems – latency, congestion, chatty applications, contention with other apps, low bandwidth – that can be addressed in a variety of ways.

Users find the secrets of WAN optimization

Here are some tips from Gartner analyst Joe Skorupa on how to analyze the problems and speed up application performance over the WAN.

* First, identify what the problem is – latency, low bandwidth, chatty applications, etc. If you assume it's low bandwidth and throw more bandwidth at the problem it won't fix the performance of a chatty application, he says.

Click to see: Quick tips on improving WAN performance

* Fix the applications. Many applications are written to run on LANs where it doesn't make much performance difference if it takes 50 round-trip transactions to paint a screen. Applications can be written with the WAN in mind to reduce the number of round trips and to encourage caching data that will be reused so it doesn't have to be fetched repeatedly. Writing better applications is a good practice going forward, but there is little chance that legacy applications will be rewritten just to deal with the WAN problem, he says.

* Boost bandwidth. It's not always the case, but sometimes all that's needed for a WAN to work better is to boost bandwidth. For WAN links in metro areas where latency is 5 millisecs and inexpensive metro Ethernet services are available, it might be simplest and cheapest to buy more bandwidth, if congestion is the primary problem. "If bandwidth is cheap, turn up the bandwidth." If it's not cheap, other methods will have to come into play.

* If latency is the primary problem, either because of distance or the nature of the application, asymmetrical acceleration may help. This optimizes data that is sent to end machines so it takes fewer bits crossing the connection to get it there. This type of optimization could include downloading browser applets that promotes, for example, caching of static data and sending only data that changes from screen to screen. "In a lot of cases it's good enough," Skorupa says.

* If latency and bandwidth are issues, symmetric acceleration may be needed via devices deployed at both ends of the WAN to deduplicate transmissions by caching bit patterns that repeat, optimizing individual applications through knowledge of how they work and how they can be assisted to work better, and compression.

* Buy a WAN emulator. These boxes can be placed between two machines and simulate a WAN connection of a certain bandwidth, latency, packet loss, etc. Businesses can then run typical traffic through the box to find out how well their mix of applications perform. CIFS, for example, may work fine with up to 25 millisec of delay on a high-bandwidth connection, so if actual links have less delay, there is likely no need to optimize the traffic on those links, he says. The emulator can also be used to test how well various WAN optimization options will work with customer applications. "They can give you a 90% confidence factor on what will work and where," Skorupa says.