This is one of a series of 9 packets corresponding to the setup and clear-down of a TCP connection. In this case the connection was made to the telnet (terminal) port of the remote computer. The computer accepts the connection and produces a login prompt to the client. Instead of proceeding to login to the server, the client then decides to terminate the connection.
This packet clears-down the telnet connection from the client to the server. The FIN (Final) bit in the TCP header is set to indicate that the client wishes the end of the connection. Normally the server would reply with another TCP packet also with the FIN bit set, confirming that the connection has been disconnected. In this case, (as shown in 9,10) the remote node decides to continue transmission.
0: 00e0 f726 3fe9 0800 2086 354b 0800 4500 ..÷&?... .5K..E.
16: 0028 08bb 4000 ff06 9998 8b85 d96e 8b85 .(..@........n..
32: e902 9005 0017 7214 f130 9431 1028 5011 ......r..0.1.(P.
48: 2238 1c64 0000 "8.d..
ETHER: ----- Ether Header ----- ETHER: ETHER: Packet 8 arrived at 17:37:31.08 ETHER: Packet size = 54 bytes ETHER: Destination = 0:e0:f7:26:3f:e9,CISCO Router ETHER: Source = 8:0:20:86:35:4b, Sun ETHER: Ethertype = 0800 (IP) ETHER: IP: ----- IP Header ----- IP: IP: Version = 4 IP: Header length = 20 bytes IP: Type of service = 0x00 (normal) IP: Total length = 40 bytes IP: Identification = 2235 IP: Flags = 0x4 IP: .1.. .... = do not fragment IP: ..0. .... = last fragment IP: Fragment offset = 0 bytes IP: Time to live = 255 seconds/hops IP: Protocol = 6 (TCP) IP: Header checksum = 9998 IP: Source address = 139.133.217.110, client IP: Destination address = 139.133.233.2, server.abdn.ac.uk IP: No options IP: TCP: ----- TCP Header ----- TCP: TCP: Source port = 36869 TCP: Destination port = 23 (TELNET) TCP: Sequence number = 1913975088 TCP: Acknowledgement number = 2486243368 TCP: Data offset = 20 bytes TCP: Flags = 0x11 TCP: ..0. .... = No urgent pointer TCP: ...1 .... = Acknowledgement TCP: .... 0... = No push TCP: .... .0.. = No reset TCP: .... ..0. = No Syn TCP: .... ...1 = Fin TCP: Window = 8760 TCP: Checksum = 0x1c64 TCP: Urgent pointer = 0 TCP: No options TCP:
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