TCP

TCP (Transmission Control Protocol ) — is an Internet transmission protocol, it is on the transport layer along with UDP, RTP. The difference between UDP and TCP is that it is more reliable.

TCP guarantees

• Delivery of data
• Preservation of message order.

Guarantee of delivery of data and preservation of an order of messages is reception of the confirming message.

An example of operation of the protocol

The sender sends a message through the network, the recipient receives it and sends an ACK to the sender (Acknowledgment; ACK means that the data segment is received). The next message is sent, and if the recipient receives it, they will send the ACK again.

This will be repeated until the sending file is received by the recipient.

Protocol operation in case of error

If an error occurs during transportation then the data segment will not reach the recipient and the recipient will not send the ASK. The sender, when sending the file, sets a timelock after which the file will be sent again if no ASK arrives. If the timer is successful, the protocol resumes sending segments until the file is finally received.

The TCP protocol acknowledges multiple segments sent one after another rather than an individual segment.

Files come to TCP as one big stream of bytes. Then, that stream is split into chunks. These chunks are called segments. Once separated, the segments are sent one after another to the addressee. The addressee, receives them, combines them into one stream and sends it to the application.

The entire sending process is protected only against the loss of segments. Received segments may not be received in the order in which they were sent. Segments may also be duplicated.