Distributed Systems Lab: Network Connections and DNS
We now come to the second part where we query the Domain Name System
Find out how it works using man pages (on Linux or on the Web).
An explanation of the output produced by dig can be found in
Connected: An Internet Encyclopedia.
1. Mail Exchange Servers
Find the mail exchange servers of unibz.it.
2. Root Servers
Find all root servers.
3. Domain Servers
Which are the name servers for the it domain?
4. Authoritative Answers
Find the IP address of www.mit.edu.
Is the answer authoritative?
Is the answer authoritative? (Hint: Check the flags in the header
and find out what they mean, looking into RFC1035.)
Contact a name server that will give you an authoritative answer.
5. Default Servers
Which are the domain names of the name servers used by default when
(or nslookup or any other resolver)
Hint: look into /etc/resolv.conf.
6. Duplicate Hosts
How many hosts can be reached under
Explain what you find.
7. Time to Live
What is the time to live of the records?
How does the time to live change when you call dig repeatedly?
Why is this the case?
Let your default name server do some caching: ask for a the name of a
rarely used machine (e.g., the ftp server of some university in some
Check how long the lookup takes the first and the
second time. Are the answers authoritative?
Can a non-authoritative DNS server return authoritative answers?
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