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Fix costly impairments with pre-deployment testing

25 Mar 2013  | Asim Rasheed

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Ensuring interoperability between devices and minimising service degradation across long distances requires limits to be set on the maximum level of the most relevant impairments present at an output interface and the minimum level that can be tolerated at an input. By adhering to these limits, network equipment designers, software creators and testers can ensure proper interworking between different vendor equipment and networks, and can isolate problems.


Impairments tend to trend
Most of us know from experience that working networks do not behave in a deterministic way. Caused by cumulative random events, impairments affect traffic packets that are traversing a network differently at any given moment. For example, when the kids in the neighbourhood get home from school, the Internet upload/download speeds slows down. Application performance is also impacted by the distance of the path that was dynamically built for each packet as it traverses a cross-country network.

Since impairments come and go with whatever is trending at the time, equipment designers, software creators, and testers need test solutions that can help to predict when and where they are most likely to occur. There are test tools available that can emulate wide area network (WAN) cloud impairments to simulate various network and cloud conditions and validate whether the end-to-end performance is impacted by the delay within the WAN cloud. These tools are leading the fight to prevent latency and packet loss.


Testing impairments
Pre-deployment impairment testing, as mentioned above, offers a controllable, simulated network environment that lets you evaluate how devices, networks, and services are impacted under various impaired traffic conditions.

This saves network designers and testers the time, effort, and money that would otherwise be spent using expensive lab resources to replicate real-life conditions. An impairment testing solution allows designers and testers to easily emulate a real-life network with a few clicks of the mouse, running network protocols and sending data traffic over an emulated device or network that has impairments impacting those packets.

When evaluating an impairment test system, designers and testers should looks for the following functions:

 • High density 1GE, 10GE, and 40GE support so the system can grow with evolving needs
 • Realistic, high-scale WAN emulation for precision testing of devices running expansive networks
 • Hardware-based impairment generation for full line rate impairments, reproduction of real-life network conditions, superior network performance, and cost-effective testing
 • Integration with traffic generation, protocol emulation, and analysis—all from a single user interface—for faster time to test, lower costs, and ease of use
 • High levels of latency to emulate long network distances and corresponding network latency (600ms delay with 10GE port pair, 6s with 1GE port pair, and 500ms delay with 40GE port pair) at line rates
 • Flexible and definable classifiers that allow the tester to impair traffic differently by class of traffic, such as QoS priority or application-specific impairment profiles
 • Emulation of large network clouds using combination of router/host emulation and impairment
Data centre operators need to be sure that the network equipment they use has been thoroughly tested and impairments vetted before they are implemented. Network equipment designers and testers can use impairment testing results to determine the best design for their devices or where to focus efforts to rectify performance problems. With the right impairment testing and reporting tools, you can demonstrate to customers that your equipment has been optimised not just as a stand-alone box, but as part of a variety of networks, running a variety of service mixes.


About the author
Asim Rasheed is technical marketing engineer for Ixia.

To download the PDF version of this article, click here.


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