DNS Protocol Analysis

Problem 2.

Given a FTP client host whose name is ksc111.keene.edu and a FTP

server host whose name is ftp.umass.edu, there is a request message sent from

the FTP client to the FTP server. In order to resolve the IP address of the FTP

server, we suppose the FTP client host will use 4 name servers, namely, a local

name server (nic.keene.edu), a root name server, an edu TLD name server, and

an authoritative name server. We assume the IP address of the edu TLD name is

cached in the root name server, and the IP address of the authoritative name

server is 128.90.78.65. Also, we assume there are 4 DNS resource records stored

in the database of the edu TLD server, namely:

(mit.edu, dns.mit.edu, NS)

(unh.edu, dns1.unh.edu, NS)

(bu.edu, dns2.bu.edu, NS)

(umass.edu, dns.umass.edu, NS)

and moreover, we assume there are 11 DNS resource records stored in the

database of the authoritative name server, namely:

(mail.umass.edu, 201.112.30.61, A)

(gaia.umass.edu, 201.112.30.63, A)

(ftp.umass.edu, ftp2.umass.edu, CNAME)

(pop.umass.edu, 201.112.30.68, A)

(ftp1.umass.edu, 201.112.30.64, A)

(ftp2.umass.edu, 201.112.30.65, A)

(www.umass.edu, 201.112.30.90, A)

(www1.umass.edu, 201.112.30.91 A)

(www.umass.edu, suncook.umass.edu, CNAME)

(www1.umass.edu, suncook1.umass.edu, CNAME)

(ftp1.umass.edu, ftp-server.umass.edu, CNAME)

Answer the following questions:

(a) Based on the DNS resource record information stored in the database of

edu TLD name server and the authoritative name server, can we obtain

the FTP servers IP address by resolving its name through the 4 name

servers? If not, what DNS record we have to include into the database of

edu TLD name server.

(10 points)

(b) Referring to the above question, what is the IP address of the FTP server if

we can resolve successfully the FTP servers name via the 4 DNS servers.

(10 points)

ROOT DNS name server edu TLDDNS local DNS name server name server nic.keene.eduauthoritative DNS name server 128.90.78.65 FTP Client ksc111.keene.edu FTP Server ftp.umass.edu ROOT DNS name server edu TLDDNS local DNS name server name server nic.keene.eduauthoritative DNS name server 128.90.78.65 FTP Client ksc111.keene.edu FTP Server ftp.umass.edu