14.8.1-packet-tracer---tcp-and-udp-communications

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 MultiServer and click the Desktop tab > Command Prompt . b. Enter the ping -n 1 192.168.1.255 command. You are pinging the broadcast address for the client LAN. 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 MultiServer window. Step 2: Generate web (HTTP) traffic. a. Switch to Simulation mode. b. Click HTTP Client and open the Web Browser from the desktop. c. In the URL field, enter 192.168.1.254 and click Go . Envelopes (PDUs) will appear in the topology window. d. Minimize, but do not close, the HTTP Client configuration window. Step 3: Generate FTP traffic. a. Click FTP Client and open the Command Prompt from the desktop b. Enter the ftp 192.168.1.254 command. PDUs will appear in the simulation window. 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 6 www.netacad.com

Packet Tracer - TCP and UDP Communications c. Minimize, but do not close, the DNS Client configuration window. Step 5: Generate Email traffic. a. Click E-Mail Client and open the E Mail tool from the Desktop. b. Click Compose and enter the following information: 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 E-Mail Client configuration window. 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 Capture/Forward button in the Simulation Panel to observe the different protocols travelling on the network. Note : The Capture/Forward button ‘ >| ‘ is a small arrow pointing to the right with a vertical bar next to it. a. Click Capture/Forward once. All of the PDUs travel to the switch. b. Click Capture/Forward six times and watch the PDUs from the different hosts as they travel on the network. Note that only one PDU can cross a wire in each direction at any given time. Questions: What is this called? Multiplexing A variety of PDUs appears in the event list in the Simulation Panel. What is the meaning of the different colors? Different types of protocols such as DNS and TCP. 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 HTTP and TCP PDUs. To filter the traffic that is currently displayed: 1) Click Edit Filters and toggle the Show All/None button. 2) Select HTTP and TCP . Click the red “x” in the upper right-hand corner of the Edit Filters box to close it. Visible Events should now display only HTTP and TCP PDUs. c. Open the browser on HTTP Client and enter 192.168.1.254 in the URL field. Click Go to connect to the server over HTTP. Minimize the HTTP Client window. d. Click Capture/Forward until you see a PDU appear for HTTP. Note that the color of the envelope in the topology window matches the color code for the HTTP PDU in the Simulation Panel. Question: Why did it take so long for the HTTP PDU to appear? TCP must first establish the connection. © 2013 - 2019 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 2 of 6 www.netacad.com

Packet Tracer - TCP and UDP Communications d. Record the SRC PORT , DEST PORT , SEQUENCE NUM , and ACK NUM values. Source Port: 1027, Destination Port 21, Seq Num 0, Ask Num 0 Question: What is the value in the flag field? The flag field is SYN e. Close the PDU and click Capture/Forward until a PDU returns to the 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? The source port and destination ports are reversed. Seq Num is 0, Ask Num 1The flag field is SYN and ACK g. Click the Outbound PDU Details tab. Question: How are the port and sequence numbers different from the previous results? The source port and destination ports are reversed. The Seq Num is 1, Ask Num is 1. h. Close the PDU and click Capture/Forward until a second PDU returns to the FTP Client . The PDU is a different color. i. Open the PDU and select Inbound PDU Details . Scroll down past the TCP section. 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 Edit Filters to display only 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? UTP 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: Sou Source Port: 1026, Destination Port 53 Why are there no sequence and acknowledgement numbers? It is UDP f. Close the PDU and click Capture/Forward until a PDU with a check mark returns to the DNS Client . g. Click the PDU envelope and select Inbound PDU Details . Question: © 2013 - 2019 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 4 of 6 www.netacad.com

Packet Tracer - TCP and UDP Communications How are the port and sequence numbers different than before? They are reversed. What is the last section of the PDU called? What is the IP address for the name multiserver.pt.ptu ? DNS Answer. IP 192.168.1.254 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 Edit Filters to display only POP3, SMTP and TCP . c. Click the first PDU envelope to open it. d. Click the Outbound PDU Details tab and scroll down to the last section. Questions: What transport layer protocol does email traffic use? TCP Are these communications considered to be reliable? Yes . e. Record the SRC PORT , DEST PORT , SEQUENCE NUM , and ACK NUM values. What is the flag field value? Source Port: 1026, Destination Port 25, Seq Num 0, Ack Num 0, SYN f. Close the PDU and click Capture/Forward until a PDU returns to the E-Mail Client with a checkmark. g. Click the TCP PDU envelope and select Inbound PDU Details . Question: How are the port and sequence numbers different than before? They are reversed, Seq Num 0, ACK Num 1 h. Click the Outbound PDU Details tab. Question: How are the port and sequence numbers different from the previous two results? Source Port: 1026, Destination Port 25, Seq Num 1, Ack Num 0, ACK i. There is a second PDU of a different color that E-Mail Client has prepared to send to MultiServer . This 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 PDU s? Source Port: 1026, Destination Port 25, Seq Num 1, Ack Num 1, ACK and PSH What email protocol is associated with TCP port 25? What protocol is associated with TCP port 110? Type your answers here. Port 25: SMTP Port 110: POP3 © 2013 - 2019 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 5 of 6 www.netacad.com