data communications and computer networks

Project Description:

using wireshark (formerly ethereal)

required hardware: you can do this lab exercise on any computer that is connected to
the internet and has ethereal or wireshark software installed. alternately, you can do
this lab from the comfort of your own home or laptop by downloading and installing
wireshark from (or ethereal from and installing
it on your local pc.

in this lab you will:
1. execute wireshark and practice capturing data packets

2. become familiar with the results from capturing packets for a file download from
a web server.

part 1: start up wireshark capture and select computer ip address
1. determine the ip address for the ethernet interface cards of the computer you
are using. start up wireshark, click capture to interfaces and click on the
check box under device corresponding to your active ethernet interface.
click on the start button. wireshark will begin running in capture mode and
will open up a wireshark capture window showing you how many packets
have been captured in real time.

part 2: download web page
1. with wireshark still running in capture mode, start up your favorite browser
(internet explorer, mozilla, firefox or whatever).

2. enter the following address:

3. a web page should appear in your browser from the author’s home page

4. close your browser window

5. go back to the wireshark capture window and click the stop button or
capture to stop to stop the packet capture.

part 3: verify that the web page download has been captured
1. back in the wireshark window, you should now see lots of packets in the top
summary pane. filter out all packets except http packets by typing the word
“http” into the filter: box and press apply or click viewfilter toolbar if
you don’t see a filter box at the top. this will make things much easier to

2. you should see a packet containing something like “get /cwhite / http”
sent by your pc to request the web page download.

3. if the next packet listed (containing the reply from the web server to your pc)
contains “http/1.1 200 ok” and the next 3 are “continuation” get packets,
then you have successfully captured the packets containing the lab html web
page. skip the following step 4 and continue to part 4.

4. on the other hand, if the reply from the web server contains “http/1.1 304
not modified”, then this means wireshark did not capture the packets from
the web site because the web page was already stored (cached) in your
browser. in this case you must clear your browser cache and then go back and
re-do the capture as follows:

a. first, you must clear the web cache in your browser.
i. for internet explorer, click tools to internet options, then, under
the general tab, click the delete files button within the
temporary internet files box area.

ii. for firefox, click tools to options, then privacy, cache and click

iii. for other browsers, you’re on your own.

b. now in your wireshark window, again select capture to interfaces and
click the capture button corresponding to the ethernet interface. when
prompted whether to save the previous capture, click continue without

c. go back to part 2, step 1 above to download the web page again while
wireshark is capturing packets.

part 4: what to hand in
the goal of this lab was primarily to introduce you to wireshark and practice capturing
data packets. the intentions of the following questions is to show that you have been able
to run wireshark and explore some of the capabilities. answer the following questions:

1. list at least three different protocols that appears in the protocol column in the
unfiltered packet-listing window.

2. how long did it take from when the http get message was sent until the http
ok reply was received? note: by default, the value of the time column in the
packet listing window is the amount of time, in seconds, since wireshark tracing
began. to display the time field in time-of-day format, select the wireshark view
pull down menu, then select time display format, then select time-of-day.

3. what is the internet address of the web page

4. what is the internet address of your computer?

5. provide screen shots of the http get and http ok messages that was sent
from your computer to the http server. look
for an http get and http ok message in the “listing of captured packets”
portion of the wireshark window that shows “get /cwhite ". when you select the
http get message, the ethernet frame, ip datagram, tcp segment, and http
message header information will be displayed in the packet-header window2. by
clicking on ‘+’ and ‘-‘ right-pointing and down-pointing arrowheads to the left
side of the packet details window, minimize the amount of frame, ethernet,
internet protocol, and transmission control protocol information displayed.
maximize the amount information displayed about the http protocol.

6. create (on paper) a simple example of a substitution-based cipher.

7. create (on paper) a simple example of a transposition-base cipher.

thank you!
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Price Type: Negotiable

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