These tools will generate traffic and transmit it, retransmit traffic from a capture file, perhaps with changes, or permit you to edit traffic in a capture file and retransmit it.
• Bit-Twist includes bittwist, to retransmit traffic from a capture file, and bittwiste, to edit a capture file and write the result to another file (GPL, BSD/Linux/OSX/Windows)
• Cat Karat is an easy packet generation tool that allows to build custom packets for firewall or target testing and has integrated scripting ability for automated testing. (Windows)
• D-ITG (Distributed Internet Traffic Generator) is a platform capable to produce traffic at packet level accurately replicating appropriate stochastic processes for both IDT (Inter Departure Time) and PS (Packet Size) random variables (exponential, uniform, cauchy, normal, pareto, …).
• epb (ethernet package bombardier) is a simple CLI tool for generating/converting ethernet packets from plain text/pcap/netmon/snoop files. (BSD like, Linux/Unix)
• Mausezahn is a free fast traffic generator written in C which allows you to send nearly every possible and impossible packet.
• Nemesis is a command-line network packet crafting and injection utility. Nemesis can natively craft and inject ARP, DNS, ETHERNET, ICMP, IGMP, IP, OSPF, RIP, TCP and UDP packets. (GPL, BSD/Linux/Solaris/Mac OSX/Win32)
• Network Expect is a framework that allows to easily build tools that can interact with network traffic. Following a script, traffic can be injected into the network, and decisions can be taken, and acted upon, based on received network traffic. An interpreted language provides branching and high-level control structures to direct the interaction with the network. Network Expect uses libwireshark for all packet dissection tasks. (GPL, BSD/Linux/OSX)
• Network Traffic Generator Client/Server based TCP/UDP traffic generator (GPL, BSD/Linux/Win32)
• Ostinato is a network packet and traffic generator and analyzer with a friendly GUI. It aims to be “Wireshark in Reverse” and thus become complementary to Wireshark. It features custom packet crafting with editing of any field for several protocols: Ethernet, 802.3, LLC SNAP, VLAN (with Q-in-Q), ARP, IPv4, IPv6, IP-in-IP a.k.a IP Tunneling, TCP, UDP, ICMP, IGMP, MLD, HTTP, SIP, RTSP, NNTP, etc. It is useful for both functional and performance testing. (GPL, Linux/BSD/OSX/Win32)
• packETH GUI/CLI Ethernet packet generator (GPL, Linux/OSX/Windows)
• PlayCap is a GUI tool for playing back pcap/Wireshark captures (GPL, Linux/Windows).
• Scapy is a powerful interactive packet manipulation program (in Python). It is able to forge or decode packets of a wide number of protocols, send them on the wire, capture them, match requests and replies, and much more. (GPL, BSD/Linux/OSX)
• tcpreplay is the opposite of tcpdump, send pcap files out of an interface (BSD, BSD/Linux/Unix)