Section G.2. TCP Segment Header

   

G.2 TCP Segment Header

This description is taken from pages 15 to 17 of RFC 793, Transmission Control Protocol.

TCP Header Format                                            0                   1                   2                   3         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |          Source Port          |       Destination Port        |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |                        Sequence Number                        |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |                    Acknowledgment Number                      |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |  Data |           |U|A|P|R|S|F|                               |     | Offset| Reserved  |R|C|S|S|Y|I|            Window             |     |       |           |G|K|H|T|N|N|                               |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |           Checksum            |         Urgent Pointer        |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |                    Options                    |    Padding    |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |                             data                              |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Source Port:  16 bits        The source port number.      Destination Port:  16 bits        The destination port number.      Sequence Number:  32 bits        The sequence number of the first data octet (byte) in this segment      (except when SYN is present). If SYN is present the sequence      number is the initial sequence number (ISN) and the first data      octet is ISN+1.      Acknowledgment Number:  32 bits        If the ACK control bit is set, this field contains the value of      the next sequence number the sender of the segment is expecting to      receive.  Once a connection is established this is always sent.      Data Offset:  4 bits        The number of 32 bit words in the TCP Header.  This indicates      where the data begins.  The TCP header (even one including options)      is an integral number of 32 bits long.      Reserved:  6 bits        Reserved for future use.  Must be zero.      Control Bits:  6  single-bit values (from left to right):        URG:  Urgent Pointer field significant      ACK:  Acknowledgment field significant      PSH:  Push Function      RST:  Reset the connection      SYN:  Synchronize sequence numbers      FIN:  No more data from sender      Window:  16 bits        The number of data octets (bytes) the sender of this segment is      willing to accept.      Checksum:  16 bits        The checksum field is the 16 bit one's complement of the one's      complement sum of all 16 bit words in the header and text.      Urgent Pointer:  16 bits        This field contains the current value of the urgent pointer as a      positive offset from the sequence number in this segment.  The      urgent pointer points to the sequence number of the octet      following the urgent data.  This field is only be interpreted      in segments with the URG control bit set.      Options:  variable        Options may occupy space at the end of the TCP header and are a     multiple of 8 bits in length.
       


    TCP/IP Network Administration
    Advanced Topics in Global Information Management, Vol. 3 (Advanced Topics in Global Information Management Series)
    ISBN: 1591402514
    EAN: 2147483647
    Year: 2001
    Pages: 181

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