The Transmission Control Protocol/Internet Protocol (TCP/IP) is a suite of protocols that governs the way data travels from one device to another.
IP is a network layer protocol and provides datagram routing services. IP’s main task is to support internetwork addressing and packet routing.
Two main protocols work at the transport layer: TCP and UDP. TCP is a reliable and connection-oriented protocol, which means it ensures packets are delivered to the destination computer. UDP is a best-effort and connectionless protocol.
TCP
TCP is referred to as a connection-oriented protocol because before any user data is actually sent, handshaking takes place between the two systems that want to communicate.
TCP provides a full-duplex, reliable communication mechanism, and if any packets are lost or damaged, they are re-sent.
UDP and TCP are transport protocols that applications use to get their data across a network.
They both use ports to communicate with upper OSI layers and to keep track of various conversations that take place simultaneously. The ports are also the mechanism used to identify how other computers access services. When a TCP or UDP message is formed, source and destination ports are contained within the header information along with the source and destination IP addresses. The combination of protocol (TCP or UDP), port, and IP address makes up a socket, and is how packets know where to go (by the address) and how to communicate with the right service or protocol on the other computer (by the port number).
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