TCP Features

   To ensure that IP datagrams are transferred in an orderly, efficient, and reliable manner, TCP implements the following features:

Connection opening: On the sending host, a process (such as web browser)  issues a request to send data (such as a URL) to a destination host (such as a web server). TCP creates an initial segment designed to open the connection between the sender and the receiver (the browser and server). In this initial contact, the two systems exchange IP addresses and port numbers (to cerate socket interface) and setup the flow control and sequencing (discussed next)

 

Flow control: one of the parameters that the sending and receiving hosts exchange is number of bytes each is willing to accept in at on time. This way, one system doesn't end up sending more data the other system can handle. This value can move up or down as the circumstances change on each machine, so the systems exchange this information constantly to ensure efficient data transfer.

 

Sequencing: Every segment is assigned a sequence number (or, technically, the first data byte in every segment is assigned a sequence number). This technique lets the receiving host reassemble any segments that arrive out of order.

 

Acknowledgement: When TCP transmits a segment, it holds  the segments a queue until the receiving TCP issues an acknowledgement that he has received the segment. If the sending TCP doesn't receive this acknowledgement it retransmits the segment.

 

Error detection: A checksum value in the header lets the receiver test the integrity of an incoming  segment. If is corrupted, the receiver fires back an error message to the sender, which then immediately retransmits the segment.

 

Connection closing: when the process on the sending host indicates that the connection should be terminated, the sending TCP sends a segment that tells the receiver that no more data will be sent and the socket should be closed.

 

      These features illustrate why Internet communication are generally reliable. They show that TCP acts as a sort chaperone for the IP datagram traveling from host to host.