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Mohamed G. Gouda					CS 356
Spring 2020						Homework 1
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Using DNS to resolve the host name:

	www.prod.ab.com

of a web server into an IP address consists of generating and 
processing of 6 messages M1, M2, ..., and M6. Describe the generation 
and processing of these 6 messages.

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Solution:
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M1:
The local DNS server already knows the IP address of a root server. Thus,
it sends a msg M1 to this root server asking for the IP address of the com
server.

M2:
The root server already knows the IP address of a com server. Thus,
it sends a msg M2 containing the IP address of the com server back to the
local DNS server.

M3:
Now the local DNS server knows the IP address of the com server. Thus,
it sends a msg M3 to the com server asking for the IP address of the 
ab.com server.

M4:
The com server already knows the IP address of the ab.com server. Thus,
it sends a msg M4 containing the IP address of the ab.com sever back to
the local DNS server.

M5:
Now the local DNS server knows the IP address of the ab.com server. Thus,
it sends a msg M5 to the ab.com server asking for the IP address of the 
www.prod.ab.com server.

M6:
The ab.com server already knows the IP adress of the www.prod.ab.com server. 
Thus, it sends a msg M6 containing the IP address of the www.prod.ab.com
server back to the local DNS server.