[cs615asa] HW5 graded

Jan Schaumann jschauma at stevens.edu
Sat Apr 2 22:39:21 EDT 2016


I've just sent out grades for HW5.  Here are a few common notes:

The assignment asked you to perform traceroutes against a number of
locations using multiple tools.  It also explicitly asked you to "Report
anything noteworthy or interesting. If anything appears surprising,
research an explanation."

This is a fairly good hint that you should expect to see something that
might warrant some research and an explanation.  If you submit a single
sentence in respons to this, then you probably have not adaequately
addressed the problem.

One of the things that should be noteworthy would be that different
visual traceroutes to 'www.stevens.edu' end up in different physical
locations.  You should have an explanation for why that is.

When looking at the different destinations and the way traffic is
routed, you should consider the RTTs, the different paths and how they
map into the real world, where/when they cross oceans or other large
obstacles, etc.

When looking at the traceroute output, you can also, as some of you have
well documented, identify the different peering relationships between
the different network service providers, which can be quite interesting.
This exercise offers a lot of opportunity to learn more about the
infrastructure of the internet.

The tcpdump output for your traceroutes should show the TTL as it's
being incremented; you should have trimmed the various DNS lookups, and
identified the final 'destination unreachable' packets.

In the DNS exercise, several of you set your server as a forwarder that
lets Google's public DNS server answer all queries.  That misses the
point of the exercise, as you were supposed to observe the DNS packets
from your DNS server going to the root servers, the gtld servers, etc.

I suspect that this was you following some online documentation without
fully understanding it.  As I've mentioned before, please always make
sure to understand what the documents you are following mean, and why
the steps they recommend are performed.

I also hope that you revisited this assignment after the last lecture
and that you were able to better identify the relevant DNS queries.


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