Packet Tracer - Investigating the TCP/IP and
OSI Models in Action
Please click here to download topology 3.2.4.6 Packet Tracer - Investigating the TCP-IP and OSI Models in Action Instructions
Topology
Objectives
Part 1: Examine HTTP Web Traffic
Part 2: Display Elements of the
TCP/IP Protocol Suite
Background
This simulation activity is intended to
provide a foundation for understanding the TCP/IP protocol suite and the
relationship to the OSI model. Simulation mode allows you to view the data contents
being sent across the network at each layer.
As data moves through the network, it is
broken down into smaller pieces and identified so that the pieces can be put
back together when they arrive at the destination. Each piece is assigned a
specific name (protocol data unit [PDU]) and associated with a specific layer
of the TCP/IP and OSI models. Packet Tracer simulation mode enables you to view
each of the layers and the associated PDU. The following steps lead the user
through the process of requesting a web page from a web server by using the web
browser application available on a client PC.
Even though much of the information
displayed will be discussed in more detail later, this is an opportunity to
explore the functionality of Packet Tracer and be able to visualize the
encapsulation process.
Part 1: Examine HTTP Web Traffic
In Part 1 of this activity, you will use
Packet Tracer (PT) Simulation mode to generate web traffic and examine HTTP.
Step 1:
Switch from Realtime to
Simulation mode.
In the lower right corner of the Packet
Tracer interface are tabs to toggle between Realtime and Simulation
mode. PT always starts in Realtime
mode, in which networking protocols operate with realistic timings. However, a
powerful feature of Packet Tracer allows the user to “stop time” by switching
to Simulation mode. In Simulation mode, packets are displayed as animated
envelopes, time is event driven, and the user can step through networking
events.
a.
Click the Simulation mode icon to switch from Realtime mode to Simulation
mode.
b.
Select HTTP from the Event List
Filters.
1)
HTTP may already be the only visible
event. Click Edit Filters to display
the available visible events. Toggle the Show
All/None check box and notice how the check boxes switch from unchecked to checked
or checked to unchecked, depending on the current state.
2)
Click the Show All/None check box until all boxes are cleared and then select
HTTP. Click anywhere outside of the Edit Filters box to hide it. The
Visible Events should now only display HTTP.
Step 2:
Generate web (HTTP) traffic.
Currently the Simulation Panel is empty.
There are six columns listed across the top of the Event List within the
Simulation Panel. As traffic is generated and stepped through, events appear in
the list. The Info column is used to
inspect the contents of a particular event.
Note: The Web Server and Web Client are displayed in the left pane. The panels
can be adjusted in size by hovering next to the scroll bar and dragging left or
right when the double-headed arrow appears.
a.
Click Web Client in the far left pane.
b.
Click the Desktop tab and click the Web
Browser icon to open it.
c.
In the URL field, enter www.osi.local and click Go.
Because time in
Simulation mode is event-driven, you must use the Capture/Forward button to display network events.
d.
Click Capture/Forward four times. There should be four events in the
Event List.
Look at the Web Client web browser page.
Did anything change?
____________________________________________________________________________________
Step 3:
Explore the contents of the
HTTP packet.
a.
Click the first colored square
box under the Event List > Info column. It may be necessary to
expand the Simulation Panel or use
the scrollbar directly below the Event
List.
The PDU Information at Device: Web Client window
displays. In this window, there are only two tabs (OSI Model and Outbound PDU
Details) because this is the start of the transmission. As more events are
examined, there will be three tabs displayed, adding a tab for Inbound PDU Details. When an event is
the last event in the stream of traffic, only the OSI Model and Inbound PDU
Details tabs are displayed.
b.
Ensure that the OSI Model tab is selected. Under the Out Layers column, ensure that the Layer 7 box is highlighted.
What is the text displayed next to the Layer 7 label? __________________________________________
What information is listed in the numbered
steps directly below the In Layers
and Out Layers boxes?
____________________________________________________________________________________
c.
Click Next Layer. Layer 4 should be highlighted. What is the Dst Port value? ______________________
d.
Click Next Layer. Layer 3 should be highlighted. What is the Dest. IP value? ______________________
e.
Click Next Layer. What information is displayed at this layer?
____________________________________________________________________________________
f.
Click the Outbound PDU Details tab.
Information listed under the PDU Details is reflective of the layers
within the TCP/IP model.
Note: The information listed under the Ethernet II section provides even more detailed information than is
listed under Layer 2 on the OSI Model
tab. The Outbound PDU Details
provides more descriptive and detailed information. The values under DEST MAC and SRC MAC within the Ethernet
II section of the PDU Details appear
on the OSI Model tab under Layer 2,
but are not identified as such.
What is the common information listed
under the IP section of PDU Details as compared to the
information listed under the OSI Model tab?
With which layer is it associated?
____________________________________________________________________________________
What is the common information listed
under the TCP section of PDU Details, as compared to the information listed under the OSI Model tab, and with which layer is
it associated?
____________________________________________________________________________________
What is the Host listed under the HTTP section
of the PDU Details? What layer would
this information be associated with under the OSI Model tab?
____________________________________________________________________________________
g.
Click the next colored square
box under the Event List > Info column. Only Layer 1 is active
(not grayed out). The device is moving the frame from the buffer and placing it
on to the network.
h.
Advance to the next HTTP Info box within the Event List and click the colored square
box. This window contains both In Layers
and Out Layers. Notice the
direction of the arrow directly under the
In Layers column; it is pointing upward, indicating the direction the
information is travelling. Scroll through these layers making note of the items
previously viewed. At the top of the column the arrow points to the right. This
denotes that the server is now sending the information back to the client.
Comparing the information displayed in the In Layers column with that of the Out Layers column, what are the major differences?
____________________________________________________________________________________
i.
Click the Outbound PDU Details tab. Scroll down to the HTTP section.
What is the first line in the HTTP
message that displays?
____________________________________________________________________________________
j.
Click the last colored square box
under the Info column. How many tabs
are displayed with this event and why?
____________________________________________________________________________________
Part 2: Display Elements of the TCP/IP Protocol Suite
In Part 2 of this activity, you will use the
Packet Tracer Simulation mode to view and examine some of the other protocols comprising
of the TCP/IP suite.
Step 1:
View Additional Events
a.
Close any open PDU information windows.
b.
In the Event List Filters >
Visible Events section, click Show All.
What additional Event Types are
displayed?
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
These extra entries play various roles
within the TCP/IP suite. If the Address Resolution Protocol (ARP) is listed, it
searches MAC addresses. DNS is responsible for converting a name (for example, www.osi.local) to an IP address. The
additional TCP events are responsible for connecting, agreeing on communication
parameters, and disconnecting the communications sessions between the devices.
These protocols have been mentioned previously and will be further discussed as
the course progresses. Currently there are over 35 possible protocols (event
types) available for capture within Packet Tracer.
c.
Click the first DNS event in the
Info column. Explore the OSI Model and PDU Detail tabs and note the encapsulation process. As you look at
the OSI Model tab with Layer 7 highlighted, a description of
what is occurring is listed directly below the In Layers and Out Layers
(“1. The DNS client sends a DNS query to the DNS server.”). This is very useful
information to help understand what is occurring during the communication
process.
d.
Click the Outbound PDU Details tab. What information is listed in the NAME: in the DNS QUERY section?
____________________________________________________________________________________
e.
Click the last DNS Info colored square box in the event
list. Which device is displayed?
____________________________________________________________________________________
What is the value listed next to ADDRESS: in the DNS ANSWER section of
the Inbound PDU Details?
____________________________________________________________________________________
f.
Find the first HTTP event in the list and click the
colored square box of the TCP event
immediately following this event. Highlight Layer 4 in the OSI Model
tab. In the numbered list directly below the In Layers and Out Layers,
what is the information displayed under items 4 and 5?
____________________________________________________________________________________
TCP manages the connecting and
disconnecting of the communications channel along with other responsibilities.
This particular event shows that the communication channel has been
ESTABLISHED.
g.
Click the last TCP event.
Highlight Layer 4 in the OSI Model
tab. Examine the steps listed directly below In Layers and Out Layers.
What is the purpose of this event, based on the information provided in the
last item in the list (should be item 4)?
____________________________________________________________________________________
Challenge
This simulation provided an example of a
web session between a client and a server on a local area network (LAN). The
client makes requests to specific services running on the server. The server
must be set up to listen on specific ports for a client request. (Hint: Look at
Layer 4 in the OSI Model tab for
port information.)
Based on the information that was
inspected during the Packet Tracer capture, what port number is the Web Server listening on for the web
request?
____________________________________________________________________________________
____________________________________________________________________________________
What port is the Web Server listening on for a DNS request?
____________________________________________________________________________________
____________________________________________________________________________________
Suggested Scoring Rubric
Activity Section
|
Question Location
|
Possible Points
|
Earned Points
|
Part 1: Examine
HTTP Web Traffic
|
Step
2d
|
5
|
|
Step
3b-1
|
5
|
||
Step
3b-2
|
5
|
||
Step
3c
|
5
|
||
Step
3d
|
5
|
||
Step
3e
|
5
|
||
Step
3f-1
|
5
|
||
Step
3f-2
|
5
|
||
Step
3f-3
|
5
|
||
Step
3h
|
5
|
||
Step
3i
|
5
|
||
Step
3j
|
5
|
||
Part 1 Total
|
60
|
||
Part 2: Display
Elements of the TCP/IP Protocol Suite
|
Step
1b
|
5
|
|
Step
1d
|
5
|
||
Step
1e-1
|
5
|
||
Step
1e-2
|
5
|
||
Step
1f
|
5
|
||
Step
1g
|
5
|
||
Part 2 Total
|
30
|
||
Challenge
|
1
|
5
|
|
2
|
5
|
||
Part 3 Total
|
10
|
||
Total Score
|
100
|
||
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