problem 1) In this problem you will use the unix utility 'dig' to explore contents of DNS messages. Please use dig on unix.andrew.cmu.edu. The format of a dig request is simple. Just type:
dig www.princeton.edu to perform a look-up for that DNS name. As you now know, DNS requests can do more than just ask for IP address corresponding to single DNS name. Type dig princeton.edu ANY to see DNS records of all types that are associated with the domain `princeton.edu'.
(a) What IP address did computer you are logged into contact to make the DNS request? Where do you think this server is located?
(b) List all of the various kinds of records received as a result of your query. For each record, describe its purpose, using one of the entries provided in the reply as the concrete ex.
(c) Note that some of the names in the reply are not in a domain `princeton.edu'. Use the DNS names and/or `traceroute' to find the general location of one of these servers. Where is it? Given the type of record, why would Princeton do this?
(d) Use dig to find the names of two non-local servers you could contact in the process of identifying the nameserver for the domain `cnn.com' (assume no DNS information is cached anywhere).
(e) Use dig to determine the TTL for the DNS mappings of `www.cnn.com' and `www.cs.stanford.edu'. What are they? If you ask to provide two positive and two negative effects of having a short DNS TTL for company's e-commerce site, what would be your answer?
problem 2)(a) IPv6 allows for 2128 addresses. That is about 295 addresses for every person alive. Why was IPv6 designed to have so many addresses? Identify two specific reasons.
(b) IPv4 contained a checksum while IPv6 does not. describe why the designers of IPv6 decided the checksum was not needed. Give at least 2 concrete reasons why they felt they could or should drop this feature.