Linux in an Embedded Communications Gateway

This article describes a communications gateway system, why Linux was chosen for the implementation and why Linux is an excellent choice for similar gateways.

This project is one of many examples of Linux being successfully used in the commercial marketplace and in mission-critical commercial communication applications. In fact, Linux may have a place in such applications where perhaps no other OS can compete.

Linux is exceptionally well-suited for communications functions. It's fast, stable, reliable, has built-in TCP/IP networking, and it uses common, well-known development tools. Commercial versions of those tools are now available from Cygnus Solutions ( Using loadable modules makes trimming the system down to a minimum kernel fairly easy to do, and the whole operating system is Open Source, so there's no limit to the customization possible.

Linux runs on many different processors, opening a wide range of target platforms—yet applications developed for it can easily be ported to other UNIX platforms, as required. The number of Linux ports to small, cheap processors is growing—Linux even runs on the Palm Pilot. Commercial technical support for Linux is available from several companies. Linux developers are getting easier to find as the popularity of the OS increases, and as more universities use Linux in their computer science labs. In addition, and perhaps most important to a commercial venture, is the lack of any license fee to use Linux. That translates into a significant cost savings for commercial products. With its technical and financial advantages, Linux may be the best option for many embedded communications systems.

The coming years will see a huge array of new commercial communications services being offered. PCS systems, new applications for wireless networks, low-earth orbit satellite networks, new utility SCADA systems, home and small office networks—all of these systems will need to be interconnected in various ways, and embedded communications systems will be built to serve these functions. These systems will range from cable-modem/video-on-demand controllers mounted high on telephone poles to small black boxes locked away in phone company central offices to small black boxes that sit behind your PC. I won't be surprised if many of these next generation systems run Linux.


Greg Herlein no longer works for Pacific Gas and Electric Company. Since building the system described here, he has gone on to adventures as network administrator on a major oceanographic research ship. He now owns and runs Herlein Engineering, a software development and consulting company that specializes in Linux, networking and communications and is based in San Francisco. You can find out more at or reach him by e-mail at