In this problem, we use the useful dig tool available on Unix and Linux

hosts to explore the hierarchy of DNS servers. Recall that in Figure $2\mathrm{.}19,$ a DNS

server higher in the DNS hierarchy delegates a DNS query to a DNS server lower in

the hierarchy, by sending back to the DNS client the name of that lower$-$level DNS

server. First read the man page for dig, and then answer the following questions.

a$.$ Starting with a root DNS server $($from one of the root servers $[$a$-$

m$].$rootservers.net$),$ initiate a sequence of queries for the IP address for your

department$$s Web server by using dig. Show the list of the names of DNS

servers in the delegation chain in answering your query.

b$.$ Repeat part a$)$ for several popular Web sites, such as google.com, yahoo.com, or

amazon.com.?