tcptraceroute is a traceroute implementation using TCP SYN packets, instead of the more traditional UDP or ICMP ECHO packets. In doing so, it is able to trace through many common firewall filters.
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This version includes greatly improved command line handling, properly aligning packet data for architectures that don't allow non-aligned memory access, the ability to traceroute to a local IP address, the ability to probe with TCP ACK packets, making it possible to traceroute through stateless firewalls that permit hosts sitting behind the firewall to establish outbound connections, and the ability to track probes by source port numbers instead of IP IDs, making it possible for tcptraceroute to function properly on Solaris.
Many new features have been introduced, including the ability to send more than one probe to each hop, to send probes with the ECN bits set, to send probes of an arbitrary length, and more.