On the Road to Building a VoIP Testbed
I plan to start working on an idea about building a testbed for Voice-over-IP experiments. Some of the experiments I would like to perform are:
- The Effect of Non-variable Delays and Jitter in the WAN interface on VoIP performance.
- The Effect of Non-variable Delays and Jitter in the LAN interface on VoIP performance.
- Comparison of the Effects of Non-variable Delays and Jitter in the LAN and WAN interfaces on VoIP performance.
- The Effect of DSL local loop saturation on VoIP performance.
- Effectivity of SS7 signalling over SIP signalling on Hybrid POTS-VoIP networks.
- … and other experiments on particular pieces of vendor provided hardware and software solutions from softswitches to hardware-based media converters.
Some of the tools that come to mind for developing this projects are:
- Asterisk SoftPBX. This is the most importat piece of technology in this project. This can serve as the media gateway controller, signalling controller and feature router all in one. Also the tests should be launched from this platform. I will probably need to write some custom plugins here to automate certain testing tasks.
- NIST-Net Network Testing Suite is a general-purpose tool for emulating performance dynamics in IP networks. The tool is designed to allow controlled, reproducible experiments with network performance sensitive/adaptive applications and control protocols in a simple laboratory setting.
- SIPp Testing Tool is an open source SIP traffic generator. This is useful for SIP protocol compliance and load testing.
- PCI E1-PRI Interface Cards. These cards from Sangoma or Digium are useful for PSTN interfacing for both calls and signalling.
- PC Hardware. Need some hardware to install all this software on. We will probably require at least one PC per testbed component. It is wise not to mix components in a single PC to make isolation and troubleshooting easier. Also this could minimize possible load sharing factors that might affect the experiments.
- Handsets. These should come in the form of PSTN, ISDN and VoIP telephone handsets. Software-based IP Phones can also be used.
- PSTN Connectivity. Connectivity to traditional PSTN systems like Class 4 and Class 5 switches.
- Network Connectivity. Two subnets can be built to emulate both WAN and LAN sides of the network. The WAN side can also be emulated on the Ateneo-PLDT Network Testbed.
There are also some commercial VoIP and network testing tools that can be used in this project. These will have to be evaluated further. The list above is just a list of bare essentials and I will probably start the project with these items. The first phase would be to evalution these components and scan the market for alternatives.
