Exam question help :(

Andy andyli1234567 at hotmail.com
Thu Apr 1 02:38:23 UTC 2004


Hello group!
 
I'm guessing this where all the experts with DNS are gathered...

I'm currently stuck on this question we have in our Networks and
Communication course in Imperial, UK! If anyone can help to any parts
of the question, it will be very much appreciated! Taken from the 2003
exam...


A web browsing session visits the following URLs in order:

http://www.doc.ic.ac.uk/index.html
ftp://kiwi.doc.ic.ac.uk/README
http://www.doc.ic.ac.uk:8080/index.html

Briefly explain your answer to each of the following:


i) How many DNS lookup operations will the browser need to perform in
the session?

I believe this to be 2, one for the two http requests and one for the
ftp request, but i'm not really sure!


ii) If the browser was situated in the java.sun.com domain, and made a
request for an iterative lookup of address from its local DNS server,
what are the domains that the DNS server contacts for the lookup of
the first URL in the list above. (it must be assummed that each level
in the DNS heirarchy is in a different zone, and that all servers have
no cached information).

I came up with this list,but i'm not too sure once again!

java.sun.com
sun.com
.com
<root>
uk
ac.uk
ic.ac.uk
doc.ic.ac.uk

iii) How many server processes will be contacted by the browser during
the session?

iv) For the first and last URL, how is the server socket constructed?

v) If the session was extended to send an email to
notab at kiwi.doc.ic.ac.uk, is a new DNS request required.

I think that it does not require a new request as its something to do
with it already being cached...?

vi) DNS does not provide user defined record types, but you are
required to add details of the owner and telephone number of each
machine in the doc.ic.ac.uk domain, which can be retrieved by outside
clients using DNS. Can you suggest a method to achieve this?

I can't! :(

vii) Explain if it would be possible or not to use a firewall to block
access to http://www.doc.ic.ac.uk/c212_exam.ps but allow access to all
URLs listed in the web browsing session.


Any help or pointers in the right direction will be a life saver as my
exams are soon!!!!

Thanks a lot people!

Andy


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