Transport Control Protocol

Seven major features of TCP
1. Connection oriented
2. Point to point
3. Complete reliability - delivered as sent
4. Full duplex communication
5. Stream interface
6. Reliable connection startup
7. Graceful connection shutdown

Connection-Oriented Service
when a Application at site A wants to send to and receive data from another application at site B, the following three phases occur:
1. The two TCPs establish a virtual connection between them.
2. Data are exchanged in both directions.
3. The connection is terminated.

Note that this is a virtual connection, not a physical connection. The TCP segment is encapsulated in an IP datagram and can be sent out of order, or lost, or corrupted, and then resent. Each may be routed over a different path to reach the destination. There is no physical connection. TCP creates a stream-oriented environment in which it accepts the responsibility of delivering the bytes in order to the other site.

Full-Duplex Communication
TCP offers full-duplex service, where data can flow in both directions at the same time. Each TCP endpoint then has its own sending and receiving buffer, and segments move in both directions.

Reliable transport
IP is unreliable
Application programmers typically require reliability (although not always)
The Transmission Control Protocol (TCP) establishes a reliable end-to-end communication service on top of IP
It uses an acknowledgment mechanism to check the safe and sound arrival of data