In this lab you will learn how to implement a traceroute application using ICMP request and reply messages. Students are strongly encouraged to first do the ICMP Ping lab before the ICMP Traceroute lab as it is done with the same approach. The checksum and header making are not covered in this lab, refer to the ICMP ping lab for that purpose, the naming of most of the variables and socket is also the same.
Traceroute is a computer networking diagnostic tool which allows a user to trace the route from a host running the traceroute program to any other host in the world. Traceroute is implemented with ICMP messages. It works by sending ICMP echo (ICMP type ‘8’) messages to the same destination with increasing value of the time-to-live (TTL) field. The routers along the traceroute path return ICMP Time Exceeded (ICMP type ‘11’ ) when the TTL field become zero. The final destination sends an ICMP reply (ICMP type ’0’ ) messages on receiving the ICMP echo request. The IP addresses of the routers which send replies can be extracted from the received packets. The round-trip time between the sending host and a router is determined by setting a timer at the sending host.
Your task is to develop your own Traceroute application in python using ICMP. Your application will use ICMP but, in order to keep it simple, will not exactly follow the official specification in RFC 1739..