Hello group! Just wondering if any experts could help me out with an
exam I’ve got coming up in Imperial, UK! I’m guessing this
is where people with this sort of knowledge are gathered. Anything
thing will help on any parts of the question!

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’m guessing 2, but I don’t really know why….


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 assumed that each level
in the DNS hierarchy is in a different zone, and that all servers have
no cached information.)

This is what I got, think its right

java.sun.com
sun.com
..com

uk
ac.uk
ic.ac.uk
doc.ic.ac.uk

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

Any help would be good! Is it just a total of the above? 8?

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

Sockets are : , but not given ip addresses here nor a
port for the first? 80 for http…

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

I’m thinking not because it’s already been 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 doc.ic.ac.uk domain, which can be retrieved by outside
clients using DNS. Can you suggest a method to do this?

I’m thinking its something to do with allocating numbers of
ports above the WKS range for each user, or I maybe on totally the
wrong track!

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
the URLs listed in the web browsing session.

Don’t have a clue about this one, any pointers?


Thanks a lot for any comments you could put down. Anything would be
useful as my exams are very soon!!!

Thanks again,

Andy