The publicly available network simulator ns has become a popular and widely used simulator for research in telecommunications networks. However, the design of ns is such that simulation of very large networks is difficult, if not impossible, due to excessive memory and CPU time requirements Extensions and enhancements to the ns simulator have been developed to allow a network simulation to be run in a parallel and distributed fashion, on a network of workstations.

The Georgia Tech Network Simulator (GTNetS) is a full-featured network simulation environment that allows researchers in computer networks to study the behavior of moderate to large scale networks, under a variety of conditions. The design philosophy of GTNetS is to create a simulation environment that is structured much like actual networks are structured. For example, in GTNetS, there is clear and distinct separation of protocol stack layers. Follow the link for more information.

BGP++ is a detailed C++ implementation of the Border Gateway Protocol for ns-2. BGP++ implementation is based on GNU Zebra routing software. In particular, Zebra BGP daemon is incorporated in a OO environment, modified to communicate with simulator's scheduler and TCP interface. BGP++ tries to introduce Zebra bgpd functionality in the simulator. The advantage of this approach is that it saves development effort since the same algorithms are not rewritten and it builds on well-tested code.   
 

NETI@home is an open-source software package that collects network performance statistics from end-systems. It has been written for and tested on the Windows and Linux operating systems, with testing for other operating systems to be completed soon. NETI@home is designed to run on end-user machines and will collect various statistics about Internet performance. These statistics will then be sent to a server at the Georgia Institute of Technology, where they
will be collected and made publicly available. We believe that this tool will give researchers much needed data on the end-to-end performance of the Internet, as measured by end-users. Our basic approach is to sniff packets sent to and received by the host and infer performance metrics based on these observed packets. NETI@home users will be able to select a privacy level that will determine what types of data will be gathered, and what will not be reported. NETI@home is designed to be an unobtrusive software system that runs quietly in the background with little or no intervention by the user, and using few resources.