For the same situation as in Exercise 4.5, which of the following is always true of the name resolution process, assuming that all name servers are configured correctly and no messages are lost?

A. If M had answered a query for the IP address corresponding to www.cslab. scholarly.edu at some time in the past, then it can respond to the current query without contacting any other name server.

B. If M has a valid IP address of a functioning name server for cslab.scholarly.edu in its cache, then M will get a response from that name server without any other name servers being contacted.

Exercise 4.5

While browsing the Web, you click on a link that identifies an Internet host named www.cslab.scholarly.edu. Your browser asks your Domain Name System (DNS) name server, M, to find an Internet address for this domain name. Under what conditions is each of the following statements true of the name resolution process?

A. To answer your query, M must contact one of the root name servers.

B. If M answered a query for www.cslab.scholarly.edu in the past, then it can answer your query without asking any other name server.

C. M must contact one of the name servers for cslab.scholarly.edu to resolve the domain name.

D. If M has the current Internet address of a working name server for scholarly.edu cached, then that name server will be able to directly provide an answer.

E. If M has the current Internet address of a working name server for cslab.scholarly. edu cached, then that name server will be able to directly provide an answer.