TCP Packet Switching

TCP Packet Switching

Communication cannot take place between two or more electronic devices unless they agree on a protocol. Internet Protocol and Transmission Control Protocol (TCP) are examples. These two together comprise a significant part of the Internet Protocol Suite, and they are commonly referred to as TCP/IP.

The World Wide Web (www), email, File Transfer Protocol (FTP), secure shell, peer-to-peer file sharing and streaming media applications all make use of TCP. It emphasizes reliability over speed. That is why users experience a degree of latency. But it is a small price to pay for the knowledge that in the huge Internet environment a great deal of connectivity and file transfer takes place all the time with relatively little signal corruption, data loss or dropout. That is due to TCP’s great ability to seek out and correct errors. What makes this work is packet transmission.

TCP moves data in a continuous, unstructured byte stream. The 32-bit sequence number field specifies the number assigned to the first byte of data in the current message. It can also be used to identify an initial sequence number to be used in the upcoming transmission.

The 32-bit acknowledgment number field can contain the value of the next sequence number that the sender of the segment is expecting to receive. The sequence number refers to the stream flowing in the same direction as the segment, while the acknowledgment number refers to the stream flowing in the opposite direction from the segment.

Important parts of the TCP protocol are establishment and termination of the connection. TCP uses a three-way handshake to establish the connection. For a client to connect to a server, first the server listens at a port prior to establishing a passive open. Then, the client creates an active open. The connection termination involves a four-way handshake. Here again each side participates in accordance with the protocol.