NANDINI_300377653_LAB4

B. Using Sniffer to study ARP requests and replies [_____/8] Since all messages exchange between any two devices on an Ethernet network will be encapsulated in Ethernet frames, it is necessary for the devices to determine each other’s physical address before messages can be exchanged. Knowing the destination’s IP address, a device can find out the corresponding MAC address by use of the Address Resolution Protocol (ARP). We will use Sniffer Wiresharkto gain a better understanding of ARP. What is the physical address (MAC address) of the Ethernet interface on the PC? 00:30:F2:CE:54:D7 What is the physical address (MAC address) of the Ethernet interface on the Server 00:E0:A3:39:DD:D3 3

C. Using Sniffer to study FTP session [_____/8] Refer to the lab work from lab#3 1. Ensure that the ftp server has been setup (the FTP server). 2. Test from PC that the ftp server is working 3. type ftp 210.100.10.51 using the user name student with password lab3 4. Transfer the file lab3t.txt from PC to the FTP server using the command: ftp> put lab3.txt 5. End the ftp session by typing quit . 6. On Sniffer1 7. Examine the packets captured and you should see some arp packets followed by some tcp and ftp packets. 8. tcp and ftp (which runs on top of tcp) packets will be displayed. 9. Examine the first tcp packets captured BEFORE the first FTP message.  For the first TCP message, which Flag is set in TCP? 10. Examine the FTP messages exchanged between the server and the client. Note that the server sent Response messages to the client, whereas the client sent Request messages to the server. 11. After client user logged in and before the transfer of the file, can you see there is another three-way handshake that TCP used to establish another connection between the two devices? In these 3 TCP packets, what are the SEQUENCE NUMBERS and ACKNOWLEGEMENT NUMBERS of these TCP messages SEQ# ACK# On Sniffer0 (PC outgoing pkts) 0 0 On Sniffer1 (Server outgoing pkts) 0 1 On Sniffer0 (PC outgoing pkts) 1 1 The second TCP connection is used by ftp for data transfer whereas the first TCP connection is for ftp control data. 12. Examine the second to last FTP packet that sent your file to the server (FTP-DATA).  Can you see the Message:Data connection already open; transfer starting 6