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, ICMPv4, ICMPv6, IGMP, MLD, HTTP, SIP, RTSP, NNTP, etc. It is useful for both functional and performance testing.
tcpdump prints a description of the contents of packets on a network interface which match a given boolean expression. It can also be run with the -w flag, which causes it to save the packet data to a file for later analysis, and/or with the -r flag, which causes it to read from a saved packet file rather than to read packets from a network interface. In all cases, only packets which match the expression will be processed by tcpdump. tcpdump logs more than just TCP, IP, or ethernet packets, but has a whole suite of decoders, including ones for USB.