The Network Workbench is network simulation software for academic investigation of Internet concepts. It was developed by Dr. Mark Pullen of the GMU Department of Computer Science and C4I Center, assisted by his students.

The latest version of Network Workbench is 4.2, released 5 May 2002. The major changes from version 4.0 are:
(4.1) Improved module architecture in the reliable transport layer (rtl) software. Although the rtl protocol is unchanged, software for the two versions is not compatible.
(4.2) Corrected an error in the reliable datalink control (DLC) function built into NW. The DLC protocol did not change, however the NW solution was incorrect for some cases in previous versions.