Always test remote app performance with a WAN emulator

When you test new applications using a WAN emulator before deployment, you ensure apps perform to remote users’ standards and requirements and make app adoption easier.

Always test remote app performance with a WAN emulator
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Many organizations deploy new applications for their remote site users without testing it on a WAN. Not testing these applications across a simulated WAN increases the possibility of performance issues during the early stages of usage because you have no idea how the application will perform once latency or jitter come in between the communication path of the client and server. 

If the application uses large amounts of bandwidth that causes congestion, then it can negatively affect the performance of other applications that share the bandwidth. A WAN emulator can enable you to measure the average bandwidth that an application may use before you deploy it. 

What is a WAN emulator?

WAN emulators allow network architects and engineers to build a WAN environment in a lab. This enables testing to occur within a lab without the use of a circuit which can be very costly. WAN emulators are inexpensive, and many costs under $3,000.  

Once the environment is built, emulators allow various parameters and characteristics of a WAN environment to be configured and applied. The most important is bandwidth.

WAN emulators can be implemented as either an appliance or software installed on a computer. They have at least two LAN interfaces and will simulate a WAN. Traffic enters the interface, and software within the emulator will buffer the traffic and slow it down, depending on the bandwidth settings that are configured. 

WAN emulators typically allow different upstream and downstream bandwidths to be configured. This is important because many circuits that organizations use are asynchronous, and it enables testers to more closely simulate their WAN environment. 

WAN emulator parameters: latency, packet loss and jitter configuration

Many WAN emulators allow users to select and configure other parameters, such as latency, jitter and packet loss. Latency exists in every WAN connection and can have a big impact on real-time communications. Voice-over-IP and video communication are some of the most sensitive applications to latency.

Packet loss varies by provider, distance and path, but it is important to test applications with non-zero packet loss and to increase packet loss settings in the test environment to find out at what point the application response becomes unacceptable. This type of flexibility is impossible in the real world because a real network has bandwidth determined by the provider and latency that is determined by the distance between network endpoints and the type of communication medium.

While a WAN might, at times, experience some level of packet loss, it is almost impossible for a production user to create such a scenario for the purposes of evaluating the behavior of an application. This is also true for jitter, which is the variation in latency. Some form of jitter is present in all WAN environments and should be included along with packet loss in the configuration to obtain an accurate measurement test or simulation.  

How to test your applications using a WAN emulator 

When testing applications with a WAN emulator, you install the server side of the application on one Ethernet interface and the client side on the other Ethernet interface. You then measure how your application performs with bandwidth, latency and jitter settings similar to what is operating on your present WAN. You establish that configuration as your baseline.  

From that point, you incrementally degrade the performance and measure the application response time. Also, from your baseline, you increment the performance and measure how your application performs at each increment level. You then document what emulator settings created acceptable and unacceptable application performance.  

It is critical to have an actual application end user involved in measuring the application performance. This will help obtain an accurate opinion of the performance. Use any application performance monitoring tools that you have available, and consider tracking time on certain transactions. It is essential to document all your emulator settings and the application response time with each specific setting.  

The next step is for network engineers and application support staff to discuss what is an optimal way to configure the network or application parameters to most effectively enable the application to work effectively across a WAN.  

Decisions about how much bandwidth is required, quality of service mechanisms, what type of circuit is best for optimal communication, etc. will be made. Your goal should be optimal application performance, without interrupting the communication of existing traffic. Using the data that is documented from the WAN emulation tests will help you make the correct decision.

End users deal with enough challenges when getting comfortable using a new or updated application interface, so it is best to make it easier for them by having it at least perform optimally across the WAN. That is why it is always best to be proactive and test the performance across the WAN before any deployment.

Taking this extra effort to test applications on a WAN emulator will make the transition to using new applications much more seamless because they will perform faster and not interrupt the performance of other applications. In the end, this can contribute to increased user productivity and a workforce that is less resistant to changes in applications.

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