TCP header format

Postingan ini saya buat dan copas langsung dari wikipedia untuk menghadapi ujian jaringan komputer, isinya ngga dilebih-lebihin maupun dikurang-kurangin. hal ini ditulis untuk menangani sifat mudah lupa saya. hha

TCP merupakan komponen paling vital pada model TCP/IP yang kita pakai. Karena dengan TCP inilah kita dapat mewujudkan aplikasi internet yang reliable, connection oriented. dibawah ini merupakan header format dari TCP

source port dan destination port adalah port sumber dan tujuan, port ini merupakan pengalamatan pada transport layer. Secara umum pada transport layer end pointnya disebut TSAP, atau Transport Serciver Access Point dan pada TCP TSAP ini disebut dengan port.

Sequence number dan Acknowledge number masing-masing terdiri dai 32 bit data, yang berisi nomor-nomor dari byte data.

Data Offset/ TCP header lenght berisi panjangnya data pada TCP header, atau berapa 32 bit word yang terpakai untuk header.

  • CWR (1 bit) – Congestion Window Reduced (CWR) flag is set by the sending host to indicate that it received a TCP segment with the ECE flag set and had responded in congestion control mechanism (added to header by RFC 3168).
  • ECE (1 bit) – ECN-Echo indicates
  • If the SYN flag is set (1), that the TCP peer is ECN capable.
  • If the SYN flag is clear (0), that a packet with Congestion Experienced flag in IP header set is received during normal transmission (added to header by RFC 3168).
  • URG (1 bit) – indicates that the Urgent pointer field is significant
  • ACK (1 bit) – indicates that the Acknowledgment field is significant. All packets after the initial SYN packet sent by the client should have this flag set.
  • PSH (1 bit) – Push function. Asks to push the buffered data to the receiving application.
  • RST (1 bit) – Reset the connection
  • SYN (1 bit) – Synchronize sequence numbers. Only the first packet sent from each end should have this flag set. Some other flags change meaning based on this flag, and some are only valid for when it is set, and others when it is clear.
  • FIN (1 bit) – No more data from sender
    • Window size (16 bits) – the size of the receive window, which specifies the number of bytes (beyond the sequence number in the acknowledgment field) that the receiver is currently willing to receive (see Flow control and Window Scaling)
    • Checksum (16 bits) – The 16-bit checksum field is used for error-checking of the header and data
    • Urgent pointer (16 bits) – if the URG flag is set, then this 16-bit field is an offset from the sequence number indicating the last urgent data byte
    • Options (Variable 0-320 bits, divisible by 32) – The length of this field is determined by the data offset field. Options 0 and 1 are a single byte (8 bits) in length. The remaining options indicate the total length of the option (expressed in bytes) in the second byte.
    • Padding – The TCP header padding is used to ensure that the TCP header ends and data begins on a 32 bit boundary.The padding is composed of zeros.[6]

    Some options may only be sent when SYN is set; they are indicated below as [SYN].

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