A Python script to emulate the functionality of the traceroute command. The script takes as a command line input the domain name of the intended receiver. It works by sending ICMP echo messages to the destination with increasing values of the IPv4 TTL Field. It listens to receive an ICMP Time Exceeded message from the routers along the path, and an ICMP Reply message from the final destination. The IP Addresses of the routers that send messages are extracted from the message header, and the round trip times are calculated using a timer on the sender.
This was done as a part of Assignment 1 for the course Computer Networking at IIT Delhi in Fall '21. Some important features are:
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I use ICMP Echo packets instead of UDP Datagrams used by the original
traceroute. This is because the UDP version relies on the assumption that the port on the destination host is not active. As mentioned here, many modern implementations have replaced UDP with ICMP (including the Windowstracert), and historical reasons for choosing UDP no longer exist. -
Libraries used include just the
socketlibrary, and thestructlibrary for packing bytes. I construct packets as well as unpack them to check header fields. -
The script contains three configuration variables, which can be customised. It doesn't provide a way to set them through command-line options however, so they will have to be changed in the source code. For instance, the
NUM_PROBESvariable sets how many probes to send out for eachttlvalue. Currently it is set to 3, like the default intraceroute.
Example Script Output
Plot of Average RTT vs Hop Number