If you are a network manager whose company is making a move offshore, beware. Offshore staffs cannot get their work done if their core business applications do not work well over WAN links. Poor performance and intermittent downtime can quickly offset any savings that might have been gained.
As a result, properly assessing how applications will behave and perform on the target WAN is important. The primary way to accomplish this task is through WAN emulation, which works by running target applications in the actual multi-tier data center environment, using a test bed network that reflects the conditions on the production network. This allows development, network and quality-assurance staff to observe the offshore end-user experience without leaving the lab. Staff can test application performance under current and projected traffic loads, as well as evaluate worst-case scenarios. Most importantly, they can nip potential problems in the bud while doing so is still inexpensive.
Applications behave differently over a real-world WAN then they do on a development or lab LAN. Latency, packet loss, jitter, bandwidth contention and other WAN characteristics all impact the delivery of IT services to the end-user.
Unfortunately, developers rarely consider these factors when they first build an application. They focus instead on issues such as application functionality and interface design. Only after they have tackled these issues do they consider the performance of the application on the network.
Addressing network performance problems in an application so late in the game often is difficult or impossible. Design and coding approaches are usually too entrenched at that point to be changed. As a result, companies may wind up trying to redesign the network to suit the application. That usually means adding more bandwidth, but not all problems can be overcome with raw bandwidth alone.
These problems can be exacerbated in an offshore situation. Distances are greater and bandwidth is more expensive. More network "hops" usually are involved, which can create more latency and bandwidth contention issues. Last-mile links may also be limited.
Three principles are important in developing an application-testing strategy:
Capture Attributes Of Your Existing WAN Infrastructure
A WAN emulation solution should automate this process, ensuring the accuracy of the WAN model, while keeping the time and cost associated with creating the model as low as possible. Such a solution should also enable the creation of "what-if" scenarios, to assess the potential impact that changes in the network-such as increased traffic or additional remote offices-may have on application performance.
Network-savvy developers should be given the option to do more sophisticated functionality and regression testing in the emulated environment. This will provide further protection against deployment problems and will optimize the quality of production code.
Published: Friday, November 19, 2004