Introduction to the TCP IP protocol stack through a role playing game

Transcript

1 Introduction to the TCP IP protocol stack through a role playing game Based on : Norman Pendegraft The TCP/IP game. In Current issues in IT education, Tanya McGill (Ed.). IGI Publishing, Hershey, PA, USA Acknowledgment: Many thanks to Ozden Nyiaz for assisting in the preparation of these slides

2 Players are organized into four-person teams that represent different computers in the network.

3 NETWORK MAP

4 NETWORK MAP

5 Each person in the team assumes the role of one layer.

6 Outgoing Messages

7 Creates messages Breaks the message into several smaller messages if necessary Addresses and routes the message Formats the message and performs error control Transmits the message to the physical layer of the destination computer

8 APPLICATION LAYER Message (Continued) ID of your computer ID of destination computer Type any message you wish to send up to 20 characters. Use a hyphen (-) to indicate spaces between words Write the message and the name of the computer to which you send the message on the blank piece of paper. This will help you understand the responses you get to your messages. Pass the message to the transport layer.

9 TRANSPORT LAYER Break the SMTP message into smaller packets. Cut the SMTP packet into two parts at the dotted line. Message (Continued)

10 Find one or two blank TCP packets. of If there is only one part of the SMTP packet, write "1 of 1" in the box. Message (Continued) If it s blank

11 SMTP of If there are two parts of the SMTP packet, write "1 of 2" on the first TCP packet. of "2 of 2" on the second TCP packet. Message (Continued)

12 Tape the SMTP packet(s) to the TCP packet(s) over the space. of From To Message Pass the message to the network layer.

13 SMTP IP Find a blank IP packet. NETWORK LAYER Final Destination Next Node Next computer s IP address in the Put the IP address of the network map PC corresponding to the PC of the To box of the SMTP packet

14 If your computer is directly connected to the final destination computer, the Next Node is the same as the final destination. Your Computer Final Destination

15 If your computer is not directly connected to the destination, you must select the best route that the message should follow and specify one of the computers to which you are connected. Your Computer Final Destination

16 IP Tape the TCP + SMTP packet to the IP packet over the space. Final Destination Next Node of Pass the message to the data link layer.

17 IP Ethernet DATA LINK LAYER Source Destination Control Message# Error : : Your computer s MAC address * 1st message 01 2nd message 02 of hyphens Put the MAC address of the PC corresponding to the PC of the Next Node box of the IP packet. Final Destination Next Node of

18 Ethernet IP Source Destination Control Message# Error Final Destination Next Node : : of Tape the SMTP + TCP + IP packet to the Ethernet packet over the space. Pass the message to the physical layer. In a few moments, the physical layer will return the packet to you.

19 Ethernet * IP SMTP PHYSICAL LAYER Data Messages Source Destination Control Message# Error : : Final Destination... Next Node... of If the Control box contains an asterisk (*) this is a data message.

20 Before transmitting the message. Determine if there will be an error in transmission by tossing two coins; if they are both heads, you will introduce an error. Change the number in the error box to your new calculation. Alternative version: You will transmit a message by giving it to the supervisor of the lab/course. He/she may decide to introduce an error (you will not know about it)

21 Ethernet IP SMTP Take a picture of the original packets via your mobile phone. Save the picture for next steps. Final Destination Next Node Source Destination Control Message# Error : :

22 Ethernet IP ORIGINAL PACKET Source Destination Control Message# Error Final Destination Next Node : : of Pass the original SMTP + TCP + IP + Ethernet packet back to the data link layer and make sure that that person understands that you are giving back the message that he/she just gave you to transmit.

23 Ethernet IP Control Messages Source Destination Control Message# Error Final Destination Next Node : : ACK or NAK of If the Control box contains an ACK or an NAK, this is a control message. Simply pass the Ethernet packet to the physical layer of the computer whose address is listed in the Destination box. Things are complicated enough without ACKs and NAKs getting destroyed.

24 Incoming Messages

25 Ethernet IP DATA LINK LAYER Source Destination Control Message# Error * Final Destination Next Node : : of If the Control box contains an asterisk (*), this is a data message. Perform error checking. Count the number of hyphens in the user data (the SMTP packet, the TCP packet, and the IP packet [but not the Ethernet packet]). If this number is the same as the number in the Error box, no errors have occurred. If they are different, an error has occurred.

26 Ethernet If no errors have occurred in data message Find a blank Ethernet packet. Source Destination Control Message# Error : : Your MAC address ACK Write the Ethernet address contained in the Source box of the incoming message Write the two-digit number contained in the Message box of the incoming message in the Message box Pass the outgoing ACK message to the physical layer.

27 Ethernet IP Remove the Ethernet packet from the incoming message, and throw the Ethernet packet away. Source Destination Control Message# Error Final Destination Next Node * : : of Pass the incoming SMTP + TCP + IP packet to the network layer.

28 Ethernet If an error has occurred in data message Find a blank Ethernet packet. Source Destination Control Message# Error : : Your MAC address NAK Write the Ethernet address contained in the Source box of the incoming message Write the two-digit number contained in the Message box of the incoming message in the Message box Pass the outgoing NAK message to the physical layer. Throw away the incoming message containing the error.

29 Ethernet If the Control box contains an ACK, this is an ACK message. Source Destination Control Message# Error : : ACK Find the original message you sent, from the photo that you have taken for next steps, that has the same message number as the ACK. Destroy the original message and the ACK.

30 Ethernet IP If the Control box contains an NAK, this is an NAK message. Source Destination Control Message# Error Final Destination Next Node : : NAK of Find the original message you sent, from the photo that you have taken for next steps, that has the same message number as the NAK. Give the original message to the physical layer to transmit again. In a few moments, the physical layer will return the packet to you. Destroy the NAK.

31 IP NETWORK LAYER If the message is addressed to you Final Destination Next Node of If it s your IP address

32 IP Remove the IP packet from the SMTP + TCP packet and throw the IP packet away Final Destination Next Node of Pass the SMTP + TCP packet to the transport layer

33 IP If the message is not addressed to you Final Destination Next Node of If it s someone else s IP address

34 IP Final Destination Next Node of Scratch out or erase the address in the Next Node box. Route the message by finding the next computer in the network map to which the message should be sent and writing its data link layer address in the Next Node box.

35 IP Remove the IP packet from the SMTP + TCP packet and throw the IP packet away Final Destination Next Node New IP Old IP of Substitute the IP part with the new one Pass the message to the transport layer.

36 TRANSPORT LAYER of If the box says "1 of 1": The message is completed.

37 Take the TCP packet off of the SMTP packet and throw away the TCP packet of Pass the SMTP packet to the application layer

38 SMTP of If the box says "1 of 2": The message is not completed. of Message (Continued) Wait for the second part of the message (2 of 2) to arrive.

39 SMTP Take the TCP packets off of both SMTP packets and throw away the TCP packets of of Message (Continued)

40 Tape the two parts of the SMTP packet back together. From To Message Message (Continued)

41 Message (Continued) Pass the SMTP packet to the application layer

42 APPLICATION LAYER Eventually, you will receive an incoming message from the transport layer that was sent to you by some other computer asking you a question. To respond to the message, you will send a message that answers the question. Follow the same steps above to send a message write your answer in the Message box. For example, if the message you received asked what your favorite color was, you might write red or blue in the Message box.