The Windows utility tracert or its Unix equivalent tracerout

The Windows ‘utility’ tracert, (or its Unix equivalent, traceroute) can be used to find the

sequence of routers through which a message is routed. Use this to find the path from your site to

some others. How well does the number of hops correlate with the RTT times from ping? How well

does the number of hops correlate with geographical distance? Another Unix utility ‘ping’ can be used

to find the RTT to various Internet hosts. Read the man page for ping, and use it to find the RTT to

www.columbia.edu in New York City, and www.qualcomm.com in California. Measure the RTT values

at different times of day, and compare the results. What do you think accounts for the difference?

Solution

In very simple words, the number of routers through which a packet passes on its way from source to destination is called hop count.

Ping utility can be used to measure the RTT. Ping generates a sequence of request-responses and measures the RTT. Traceroute utility can be used to measure the hop count.

Following observations were made by me regarding RTT and hop count to the given web servers:

Hop Count

Commands used : ping <webserver>, traceroute <webserver>.   for ex. traceroute www.qualcomm.com

You can try this multiple times at different times of day as mentioned in the given question.

Generally, the RTT values increase with the increasing hop cont. Sometimes, different routes have different relationships between these two measures. Geographically far hops contribute far more propagation delay than the near ones.