Ostinato is a free, open-source, cross-platform packet, traffic generator and analyzer with a user-friendly GUI. It is designed to be the reverse of Wireshark and thus be complementary to it. This program allows users to open, edit, replay, and save PCAP files, as well as modify any field of any protocol (some protocols even allow for the changing of packet fields for each packet during runtime, such as IP/MAC addresses).
