NIST Net network emulator: drop tail modification

By default the NIST Net emulator manages the router queue by dropping packets using the DRD algorithm. Some users of NIST Net wanted the emulator to do normal drop tail. Some we tried to set the DRD min and max parameters close together, but even above max DRD drops packets with a maximum p of 0.95. We hacked in a simple drop tail implementation, modifying the kernel/knistnet.c source code file. We didn't want to modify the interface or anything so we abuse the DRD max queue length parameter.

So to set up NIST Net doing drop tail with maximum queue length of mq, you can use this syntax from the command line:

$ cnistnet [your nistnet commands] --drd 0 mq

Be sure to setup a bandwidth/delay limit to build the queue up or you won't notice all but the smallest settings for max queue length. This is totally research grade software, so you should grep for jnick to ensure that it is doing what you think it is. You can download the source code below and read about compilation and installation on the NIST Net page, they remain the same with our modification. If you have other questions contact us via the information at the bottom of this page or check out the NIST Net FAQ.

Streaming Media Lab
Computer Science Department
Worcester Polytechnic Institute

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Last modified: 06/22/2003