What is TCP/IP?



Transmission Control Protocol (TCP) and Internet Protocol (IP) are two distinct computer network protocols. It is the basic communication protocol of the Internet. It can also be used as a communications protocol in a private network like; intranet or extranet.
A so-called "connection-oriented" protocol, TCP works by establishing a virtual connection between two devices via a series of request and reply messages sent across the physical network.

A protocol is an agreed-upon set of procedures and rules. When two computers follow the same protocols - the same set of rules - they can understand each other and exchange data. TCP and IP are so commonly used together, however, that TCP/IP has become standard terminology for referring to this suite of protocols.

TCP/IP is a two-layer program. The higher layer, Transmission Control Protocol, manages the assembling of a message or file into smaller packets that are transmitted over the Internet and received by a TCP layer that reassembles the packets into the original message.

The lower layer, Internet Protocol, handles the address part of each packet so that it gets to the right destination. Each gateway computer on the network checks this address to see where to forward the message. Even though some packets from the same message are routed differently than others, they'll be reassembled at the destination.
The Transmission Control Protocol is responsible for ensuring the reliable transmission of data across Internet-connected networks. TCP checks packets for errors and submits requests for re-transmissions if any are found.
Many Internet users are familiar with the even higher layer application protocols that use TCP/IP to get to the Internet. These include the World Wide Web's Hypertext Transfer Protocol, File Transfer Protocol, Telnet, and the Simple Mail Transfer Protocol.
TCP/IP Header