Ping and Traceroute for internet

From the 6.033 assignment on "Internet Routes and Measuring Round Trip Times," I learned to use ping, which sends ICMP (similar to IP) request packets, for example: ping -c 10 -s 56 www.csail.mit.edu


But ping doesn't work for www.microsoft.com and some other sites, because they block ICMP due to security reasons. But most sites don't block ICMP because, ICMP is way, way more than "traceroute" and "ping." It is used for feedback when you run a DNS server (port unreachable) which, in a modern DNS server, may actually help select a different machine to query faster. (source)

Then we used traceroute, which prints the route packets trace to network host. According to its man page, It utilizes the IP protocol's time to live (TTL) field and attempts to elicit an ICMP TIME_EXCEEDED response from each gateway along the path to the host.