Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
iperf - A TCP, UDP, and SCTP network bandwidth measurement tool
netcat - Netcat is a featured networking utility which reads and writes data across network connections...
netperf - Netperf is a benchmark that can be used to measure the performance of many different types of networking. It provides tests for both unidirectional throughput, and end-to-end latency. - HewlettPack...
Ettercap - Ettercap is a suite for man in the middle attacks on LAN.
TamoSoft Throughput Test - TamoSoft Throughput Test is a utility for testing the performance of a wireless or wired network.