Advanced Packet Data Testing with Linux

At Nortel Networks, we have developed a Linux-based system for testing a second-generation packet radio service. During system development we explored the details of packet radio, the IP internals of the Linux operating system and device-driver development.

Using our USN device, the ND environment variable and our Xnest-user environment, we provide Nortel Networks' GPRS developer with a desktop testing environment where they can exercise the latest GPRS nodes simulating mobile web surfers and the Internet.

Linux's open network code made all our work possible. Using Alessandro Rubini's Linux Device Drivers (see Resources 3) and the Linux source code as a guide, we developed a device driver in a very short amount of time, even though we had never before written a device driver. Rubini's book also helped us during our kernel modifications. It is hard to imagine being able to do something this complex in such a short period of time with a closed-source OS.

It is interesting to compare different versions of the Linux kernels. The kernel's networking code is becoming more modular and incorporates IPv6. With the latest kernel versions, all our device driver and kernel modifications would have been unnecessary. In addition to books such as Rubini's and being open source, Linux is a capable choice for any networking application because of the standards it supports and the constant improvements the Linux development community provides.


Wes Erhart ( majored in electrical engineering at Texas A&M. He joined Nortel Networks in 1993 and has been managing the GSM automation development group for two years. Not a particularly good coder and harboring an irrational distrust of all computers, Wes did possess enough good sense to marry a goddess and now has a wonderful daughter godette filling his life.

Joseph Bell ( is a Texas A&M University computer engineering graduate and has been with Nortel Networks since he was a sophomore in college. He enjoys all things Linux and anything that can be programmed. When not coding, he can be found ranching on his farm in north Texas.

Marc Hammons ( is a University of Texas computer science graduate and has been with Nortel Networks since 1994. He has lost all faith in nihilism and is a born-again Linux enthusiast. In his spare time, he enjoys digging into source code, a good cup of coffee and the game of foosball.

Mark Mains ( graduated from LSUS with three degrees, in Physics, Math and Computer Science. He started work for Nortel Networks in 1997 and has been using Linux since 1996. Most of his spare time is spent in front of his computer, building circuits or working on his Z28.


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