14.8.1 Packet Tracer - TCP and UDP Communications

10/21/23, 7:37 PM 14.8.1 Packet Tracer - TCP and UDP Communications about:blank 1/5 Packet Tracer - TCP and UDP Communications Objectives Part 1: Generate Network Traffic in Simulation Mode Part 2: Examine the Functionality of the TCP and UDP Protocols Background This simulation activity is intended to provide a foundation for understanding TCP and UDP in detail. Packet Tracer simulation mode provides you the ability to view the state of different PDUs as they travel through the network. Packet Tracer Simulation mode enables you to view each of the protocols and the associated PDUs. The steps outlined below lead you through the process of requesting network services using various applications that are available on a client PC. You will explore the functionality of the TCP and UDP protocols, multiplexing, and the function of port numbers in determining which local application requested the data or is sending the data. Packet Tracer will not score this activity. Instructions Part 1: Generate Network Traffic in Simulation Mode and View Multiplexing Step 1: Generate traffic to populate Address Resolution Protocol (ARP) tables. Perform the following task to reduce the amount of network traffic viewed in the simulation. a. Click and click the tab > . MultiServer Desktop Command Prompt b. Enter the command. You are pinging the broadcast address for the client LAN. ping -n 1 192.168.1.255 The command option will send only one ping request rather than the usual four. This will take a few seconds as every device on the network responds to the ping request from MultiServer. c. Close the window. MultiServer Step 2: Generate web (HTTP) traffic. a. Switch to Simulation mode. b. Click and open the from the desktop. HTTP Client Web Browser c. In the URL field, enter and click . Envelopes (PDUs) will appear in the topology window. 192.168.1.254 Go d. Minimize, but do not close, the HTTP Client configuration window. Step 3: Generate FTP traffic. a. Click and open the from the desktop FTP Client Command Prompt b. Enter the command. PDUs will appear in the simulation window. ftp 192.168.1.254 c. Minimize, but do not close, the FTP Client configuration window. Step 4: Generate DNS traffic. a. Click DNS Client and open the . Command Prompt b. Enter the nslookup multiserver.pt.ptu command. A PDU will appear in the simulation window. © 2013 - 2019 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 1 of 5 www.netacad.com

10/21/23, 7:37 PM 14.8.1 Packet Tracer - TCP and UDP Communications about:blank 2/5 Packet Tracer - TCP and UDP Communications c. Minimize, but do not close, the configuration window. DNS Client Step 5: Generate Email traffic. a. Click and open the tool from the Desktop. E-Mail Client E Mail b. Click and enter the following information: Compose 1) To: user@multiserver.pt.ptu 2) Subject: personalize the subject line 3) E-Mail Body: personalize the Email c. Click . Send d. Minimize, but do not close, the configuration window. E-Mail Client Step 6: Verify that the traffic is generated and ready for simulation. There should now be PDU entries in the simulation panel for each of the client computers. Step 7: Examine multiplexing as the traffic crosses the network. You will now use the in the Simulation Panel to observe the different protocols Capture/Forward button travelling on the network. Note Capture/Forward >| : The button ‘ ‘ is a small arrow pointing to the right with a vertical bar next to it. a. Click once. All of the PDUs travel to the switch. Capture/Forward b. Click six times and watch the PDUs from the different hosts as they travel on the Capture/Forward network. Note that only one PDU can cross a wire in each direction at any given time. Questions: What is this called? conversation multiplexing. A variety of PDUs appears in the event list in the Simulation Panel. What is the meaning of the different colors? They represent different protocols. Part 2: Examine Functionality of the TCP and UDP Protocols Step 1: Examine HTTP traffic as the clients communicate with the server. a. Click . Reset Simulation b. Filter the traffic that is currently displayed to only and PDUs. To filter the traffic that is currently HTTP TCP displayed: 1) Click and toggle the Edit Filters Show All/None button. 2) Select . Click the red “x” in the upper right-hand corner of the Edit Filters box to close HTTP and TCP it. Visible Events should now display only HTTP and TCP PDUs. c. Open the browser on HTTP Client and enter in the URL field. Click to connect to the 192.168.1.254 Go server over HTTP. Minimize the HTTP Client window. d. Click until you see a PDU appear for HTTP. Note that the color of the envelope in the Capture/Forward topology window matches the color code for the HTTP PDU in the Simulation Panel. © 2013 - 2019 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 2 of 5 www.netacad.com

10/21/23, 7:37 PM 14.8.1 Packet Tracer - TCP and UDP Communications about:blank 4/5 Packet Tracer - TCP and UDP Communications Question: Are these communications considered to be reliable? Yes d. Record the , , , and values. SRC PORT DEST PORT SEQUENCE NUM ACK NUM Question: What is the value in the flag field? 1025, 21, 0, 0. SYN e. Close the PDU and click until a PDU returns to the Capture/Forward FTP Client with a checkmark. f. Click the PDU envelope and select . Inbound PDU Details Question: How are the port and sequence numbers different than before? 21, 1025, 0, 1. SYN+ACK. The source and destination ports are reversed, and the acknowledgement number is 1. g. Click the tab. Outbound PDU Details Question: How are the port and sequence numbers different from the previous results? 1025, 21, 1, 1. The source and destination ports are reversed, and both sequence and acknowledgement numbers are 1. h. Close the PDU and click until a second PDU returns to the Capture/Forward FTP Client . The PDU is a different color. i. Open the PDU and select . Scroll down past the TCP section. Inbound PDU Details Question: What is the message from the server? “Welcome to PT Ftp server” j. Click Reset Simulation. Step 3: Examine DNS traffic as the clients communicate with the server. a. Repeat the steps in Part 1 to create DNS traffic. b. In the Simulation Panel, change to display only . Edit Filters DNS and UDP c. Click the PDU envelope to open it. d. Look at the OSI Model details for the outbound PDU. Question: What is the Layer 4 protocol? UDP Are these communications considered to be reliable? No e. Open the Outbound PDU Details tab and find the UDP section of the PDU formats. Record the SRC PORT and DEST PORT values. Question: Why are there no sequence and acknowledgement numbers? Because UDP does not need to establish a reliable connection. f. Close the and click until a PDU with a check mark returns to the . PDU Capture/Forward DNS Client g. Click the PDU envelope and select . Inbound PDU Details © 2013 - 2019 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 4 of 5 www.netacad.com

10/21/23, 7:37 PM 14.8.1 Packet Tracer - TCP and UDP Communications about:blank 5/5 Packet Tracer - TCP and UDP Communications Question: How are the port and sequence numbers different than before? The source and destination ports are reversed What is the last section of the called? What is the IP address for the name PDU multiserver.pt.ptu ? DNS ANSWER, 192.1681.254. h. Click Reset Simulation. Step 4: Examine email traffic as the clients communicate with the server. a. Repeat the steps in Part 1 to send an email to user@multiserver.pt.ptu . b. In the Simulation Panel, change to display only Edit Filters POP3, SMTP TCP and . c. Click the first PDU envelope to open it. d. Click the tab and scroll down to the last section. Outbound PDU Details Questions: What transport layer protocol does email traffic use? TCP Are these communications considered to be reliable? Yes e. Record the , , , and values. What is the flag field SRC PORT DEST PORT SEQUENCE NUM ACK NUM value? 1025, 25, 0, 0. SYN f. Close the and click until a PDU returns to the with a checkmark. PDU Capture/Forward E-Mail Client g. Click the TCP PDU envelope and select . Inbound PDU Details Question: How are the port and sequence numbers different than before? the source and destination ports are reversed h. Click the tab. Outbound PDU Details Question: How are the port and sequence numbers different from the previous two results? he source and destination ports are reversed i. There is a second of a different color that has prepared to send to . This PDU E-Mail Client MultiServer is the beginning of the email communication. Click this second PDU envelope and select Outbound PDU Details . Questions: How are the port and sequence numbers different from the previous two s? PDU he source and destination ports are reversed What email protocol is associated with TCP port 25? What protocol is associated with TCP port 110? SMTP. POP3. End of document © 2013 - 2019 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 5 of 5 www.netacad.com