Welcome back for another episode of the ABC's of NSM.  What's NSM you say?  We'll go with Network and System Management, but you could throw Security in there as well.  We'll work our way through the alphabet over the next several weeks looking at tools and concepts along the way for all the administrators out there.  By the way, you can thank Joe for the format & Don for the title (I couldn't for the life of me come up with one.)

Today's letter D is for DummyNet, a network protocol testing package first implemented in 1998 in the BSD operating system.  With a PC, two network interface cards and a bootable drive (take your pick), you can implement transparently between your test sources and targets.  DummyNet is configured through pipes.  First, you create the pipe, then you can constrain bandwidth, and/or set queue size, delay, and loss.  For the Linux users out there, NetEm is the most similar to BSD's DummyNet.

The value in using packages like DummyNet or NetEm comes from being able to emulate the problems your users will face in non-LAN conditions.  Delivering WAN-like obstacles in the path between your test suite and the application during the design and test cycles will give the application owners and the network administrators ample opportunities to tune where necessary to increase the likelihood of a smooth rollout into production.