Definition
Transmission Control Block
A transmission control block (TCB) is a data structure maintained by a host for every open TCP connection. It records the connection state and the sequence numbers used to ensure reliable delivery.
Contents
TCB fields
The TCB stores:
- the IP address and port number of each party;
- the sequence number of the next byte to be sent;
- the sequence number of the last sent byte that has been acknowledged;
- the sequence number of the next byte expected from the other party;
- the initial sequence numbers chosen by both parties.