Computer Networking / Assignment n. 3
Due Date: May 2nd 2006, 18:00 CEST
DNS and SMTP
This is an individual assignment. You may discuss it with others, but your answers must be written
on your own. Office hours are currently posted on the class web-site. All announcements in relation to
this assignment will also be posted there.
Problem 1: DNS
Answer the following questions about DNS:
1. Explain briefly each field in a DNS register
2. What is the role of DNS root and authority servers?
3. Use the application dig to locate the IP address of the machine www.ic.unicaamp.br. What is
the IP address? What is the canonical name of the machine?
4. Also using dig find out the name of servers with authority over the unicamp.br and br domains.
Problem 2: SMTP
1. Explain the difference between SMTP and protocols like POP and IMAP.
2. Are the connections used by SMTP persistent or not? Why?
3. Attached with this assignment are two mail messages received by leonardo@ic.unicamp.br.
Which of the two messages is likely to be authentic? Why? What machine was used to forge
the forged message?
4. Forge a message in the name of your favorite celebrity or character to leonardo@ic.unicamp.br.
Include a new SMTP header of the form X-CN2006-A03: Your Real Name. Include your real
name also somewhere in the message for grading purposes.
Problem 3: SMTP and DNS
1. Find five e-mail addresses outside the USI domains on the web. For each address, write the
canonical names and IP addresses of all the mail servers that handle the address. For example,
this is what you should write for fernandl@lu.unisi.ch
fernandl@lu.unisi.ch mg1.ti-edu.ch 195.176.176.161
mg2.ti-edu.ch 195.176.176.168
Useful References
• Lecture notes;
• Chapter two of the course book;
• dig man page;
• RFC 2821 - Simple Mail Transfer Protocol (http://www.faqs.org/rfcs/rfc2821.html)
Submission
Please turn in a pdf file containing your answers. Send the file to Leonardo via e-mail (fernandl@lu.unisi.ch)
by the deadline. In the subject of the message include the words “NET Assignment 03”.
1
Message A:
Return-Path: <leonardoleiriafernandes@gmail.com>
X-Original-To: leonardo@brasilia.ic.unicamp.br
Delivered-To: leonardo@brasilia.ic.unicamp.br
Received: from localhost (goiania.ic.unicamp.br [143.106.7.22])
by brasilia.ic.unicamp.br (Postfix) with ESMTP id 7AA7E7E10
for <leonardo@brasilia.ic.unicamp.br>; Mon, 10 Apr 2006 04:47:39 -0300 (BRST)
Received: from brasilia.ic.unicamp.br ([143.106.7.34])
by localhost (goiania.ic.unicamp.br [143.106.7.22]) (amavisd-new, port 10024)
with ESMTP id 27608-04 for <leonardo@brasilia.ic.unicamp.br>;
Mon, 10 Apr 2006 04:47:36 -0300 (BRST)
Received: from maceio.ic.unicamp.br (maceio.ic.unicamp.br [143.106.7.31])
by brasilia.ic.unicamp.br (Postfix) with ESMTP id 9B3FA7E0E
for <leonardo@brasilia.ic.unicamp.br>; Mon, 10 Apr 2006 04:47:37 -0300 (BRST)
Received: from nproxy.gmail.com (nproxy.gmail.com [64.233.182.185])
by maceio.ic.unicamp.br (8.13.6/8.11.6) with ESMTP id k3A7lMDV015292
for <leonardo@ic.unicamp.br>; Mon, 10 Apr 2006 04:47:23 -0300
Received: by nproxy.gmail.com with SMTP id p48so553127nfa
for <leonardo@ic.unicamp.br>; Mon, 10 Apr 2006 00:47:25 -0700 (PDT)
DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws;
s=beta; d=gmail.com;
Received: by 10.48.216.15 with SMTP id o15mr3490006nfg;
Mon, 10 Apr 2006 00:47:22 -0700 (PDT)
Received: by 10.48.30.8 with HTTP; Mon, 10 Apr 2006 00:47:19 -0700 (PDT)
Message-ID: <f9ca498d0604100047n60d5b3b4kc3d76c17f6742193@mail.gmail.com>
Date: Mon, 10 Apr 2006 09:47:19 +0200
From: "Leonardo Fernandes" <leonardoleiriafernandes@gmail.com>
To: leonardo@ic.unicamp.br
Subject: Hello
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
X-Virus-Scanned: by amavisd-new at ic.unicamp.br
X-Spam-Status: No, hits=5.066 tagged_above=2 required=6.31 tests=AWL,
BAYES_99, RCVD_IN_BL_SPAMCOP_NET, SUB_HELLO
X-Spam-Level: *****
Hello,
Just playing a little bit with SMTP.
-Leonardo Leiria Fernandes
PhD Student
Faculty of Informatics
University of Lugano - Switzerland
2
Message B:
Return-Path: <leonardoleiriafernandes@gmail.com>
X-Original-To: leonardo@brasilia.ic.unicamp.br
Delivered-To: leonardo@brasilia.ic.unicamp.br
Received: from localhost (goiania.ic.unicamp.br [143.106.7.22])
by brasilia.ic.unicamp.br (Postfix) with ESMTP id 35F647E10
for <leonardo@brasilia.ic.unicamp.br>; Mon, 10 Apr 2006 05:38:23 -0300 (BRST)
Received: from brasilia.ic.unicamp.br ([143.106.7.34])
by localhost (goiania.ic.unicamp.br [143.106.7.22]) (amavisd-new, port 10024)
with ESMTP id 32406-11 for <leonardo@brasilia.ic.unicamp.br>;
Mon, 10 Apr 2006 05:38:21 -0300 (BRST)
Received: from maceio.ic.unicamp.br (maceio.ic.unicamp.br [143.106.7.31])
by brasilia.ic.unicamp.br (Postfix) with ESMTP id 9CCE37E0E
for <leonardo@brasilia.ic.unicamp.br>; Mon, 10 Apr 2006 05:38:22 -0300 (BRST)
Received: from nproxy.gmail.com (rabico.lsd.ic.unicamp.br [143.106.24.138])
by maceio.ic.unicamp.br (8.13.6/8.11.6) with SMTP id k3A8YoPB021990
for <leonardo@ic.unicamp.br>; Mon, 10 Apr 2006 05:35:46 -0300
Date: Mon, 10 Apr 2006 05:34:50 -0300
Message-Id: <200604100835.k3A8YoPB021990@maceio.ic.unicamp.br>
From: "Leonardo Fernandes" <leonardoleiriafernandes@gmail.com>
To: leonardo@ic.unicamp.br
Subject: Hello
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
X-Virus-Scanned: by amavisd-new at ic.unicamp.br
X-Spam-Status: No, hits=4.557 tagged_above=2 required=6.31 tests=BAYES_90,
SUB_HELLO
X-Spam-Level: ****
Hello,
Just playing a little bit with SMTP.
-Leonardo Leiria Fernandes
PhD Student
Faculty of Informatics
University of Lugano - Switzerland
3