COMP3221 Lab 2 Routing and Communicating
The goal of this lab is to apply a routing algorithm and to connect to a remote machine on the network.
Exercise 1: Router Information Protocol (RIP)
Execute (by hand) the RIP protocol on the communication graph represented in Figure 1 where nodes represent routers and edges represent communication links between routers.
Consider initially that the routing tables are empty (containing only node-local information). Given that no failures occur (neither message losses, nor node failures), write down the final routing table each router obtains after convergence of the protocol.
What happens if the link 1 fails?
Duration: 25 min
Exercise 2: Talking to an SMTP server
The second part consists in understanding the interaction between a client and a server. Your machine will play the role of a client communicating with the ¡°Simple Mail Transfer Protocol¡± (SMTP) server whose hostname is mail.usyd.edu.au.
The language used in this communication is defined by the SMTP protocol specified in the RFCs. SMTP is associated a specific port, number 25, so that the server expects to hear the client using this specific language that sends a request to this port.
To initiate a connection on port 25 with mail.usyd.edu.au, use the terminal emulation protocol for TCP/IP through the telnet command as follow:
1 $ telnet mail.usyd.edu.au 25
The server should answer something along these lines if the connection is successful.
1 Trying 129.78.8.1…
2 Connected to mail.usyd.edu.au.
3 Escape character is ‘^]’.
4 220 staff.cs.usyd.edu.au. V1.4 ready at Mon, 02 Jul 2012 10:05:29 +1000
Try telling him HELO hostname with any hostname and observe the response from the server. Leave the connection open and continue with the next question.
1
Figure 1: A communication graph with routers A, B, C, D, E communicating through links 1,2,3,4,5,6.
Duration: 5 min
Exercise 3: Asking for a layered service
Now that the connection is opened, the next step is to ask the SMTP server to send an email. Try to send an email from your email account at the School of IT to yourself, use a different recipient address if you have one.
MAIL FROM:isusedtoindicatethesenderofthemessage.Useanglebracketstoencapsulate your email, and terminate by pressing the ¡°enter¡± key, as follows:
1 MAIL FROM:
If the server accepts the address by returning code 250, then tell him the recipient address.
1 RCPT TO:
If the server accepts the address by returning code 250, then you can start giving the data to
be sent by typing:
COMP3221 Routing and Communicating
A1B 34C
D6E
Table of router C
2 5
Table of router A
Table of router D
Table of router B
Table of router E
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1 DATA
Make sure that the server answers you how to indicate that you are done writing your data: ¡°end with a ¡¯.¡¯ on a line¡±. The last thing to do (next question below) is to write a structured message with the appropriate fields so that the email client of your recipient, once connecting to its receiving mail server (IMAP), will nicely represent this information on the screen of his computer.
Duration: 5 min
Exercise 4: Formating a message
The email information itself is represented in a format specified in another RFC. First, tell the server the format of the content (use the MIME format version 1.0):
1 MIME-Version: 1.0
Specify the correct UTC hour with +1000 indicating that Sydney time is 10 hours 00 minutes
later.
1 Date: Mon, 15 Aug 2012 15:05:00 +1000
Specify your information, the recipient information, the subject and body of the message,
and that this is a text message followed by an empty line followed by a dot.
1 From: Your name
2 To: You
3 Subject: Testing SMTP
4
5 The body of my message…
6 …spans multiple lines.
7 Content-Type: text/plain;
8
9.
Check whether you successfully received the message by using your web browser. Repeat
questions 3 and 4 with the following fields:
1 From: Satoshi Nakamoto
2 To: You
3 Subject: The Red Belly Blockchain Rocks!
What do you see? Finally, terminates the connection with:
1 QUIT Duration: 10 min
COMP3221 Routing and Communicating
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Exercise 5: Client-server communication
You can use telnet to connect to the blockchain server as well. In this tutorial, your tutor will set up a reference blockchain server for you. Ask your tutor the IP address and port number of the server. You could try to log your preferred messages with “tx|
Duration: 5 min
COMP3221 Routing and Communicating
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