TCP Packet Header Flashcards
TCP Packet Header
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
|————-Source Port ———————- | ————————Destination port ———————-|
|——————————————- Sequence Number —————————————————–|
|————————————— Acknowledgment Number ———————————————–|
|Offset|Reserved|—-TCP Flags ———–| — Window —————————————————–|
/ C E U A P R S F \
|———————Checksum—————–| ———-Urgent Pointer ————————————–|
|————————————–TCP Options (Variable length, optional) ——————————|
Source Port =
The (software) port number of the source host. (16 bits)
Destination Port =
The (software) port number of the destination host. (16 bits)
Sequence Number =
The sequence number of the first data octet in this segment. (32 bits) (Not used when the SYN flag is set.)
Acknowledgement Number =
The sequence number of the next data octet to be sent by the source. This field is used when the ACK flag is set. (32 bits)
Data Offset =
The number of 32 bit words in the TCP Header.
Reserved =
These bits should be set to 0.
Flags (Contains control information used for connection establishment)
0 1 2 3 4 5
URG ACK EOL RST SYN FIN
Flags (Contains control information used for connection establishment)
0 1 2 3 4 5
URG ACK EOL RST SYN FIN
URG =
The Urgent Pointer field is significant
ACK =
The Acknowledgement field is significant
EOL =
End of Letter
RST =
Reset the connection
SYN =
Synchronize sequence numbers
FIN =
No more data from the sender
Window =
The maximum number of octets which the sender will accept. (16 bits)
