11: TCP Reset Connection

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 sent by the client completes the TCP disconnection and resets the connection. Note that this must be the final packet in the session. Normally a sender expects a FIN (final) disconnection request to be confirmed; however a reset requires no confirmation and aborts the connection immediately. No further data should flow in either direction.


Hexadecimal Dump of the Packet

           0: 00e0 f726 3fe9 0800 2086 354b 0800 4500    ..÷&?... .5K..E.
          16: 0028 08bc 4000 ff06 9997 8b85 d96e 8b85    .(..@........n..
          32: e902 9005 0017 7214 f131 0000 0000 5004    ......r..1....P.
          48: 2238 c0c9 0000                             "8....
          64: fd27 fffd 24                            .'..$


Decode of the Packet

ETHER:  ----- Ether Header -----
ETHER:
ETHER:  Packet 11 arrived at 17:37:32.18
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
IP:         xxx. .... = 0 (precedence)
IP:         ...0 .... = normal delay
IP:         .... 0... = normal throughput
IP:         .... .0.. = normal reliability
IP:   Total length = 40 bytes
IP:   Identification = 2236
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 = 9997
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 = 1913975089
TCP:  Acknowledgement number = 0
TCP:  Data offset = 20 bytes
TCP:  Flags = 0x04
TCP:        ..0. .... = No urgent pointer
TCP:        ...0 .... = No acknowledgement
TCP:        .... 0... = No push
TCP:        .... .1.. = Reset
TCP:        .... ..0. = No Syn
TCP:        .... ...0 = No Fin
TCP:  Window = 8760
TCP:  Checksum = 0xc0c9
TCP:  Urgent pointer = 0
TCP:  No options
TCP:


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