Layer 4: TCP and UDP

Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) are the transport protocols (OSI Layer 4) for the TCP/IP protocol suite. The transport layer, as you might recall, provides the network-independent process connection services between host client/server applications. These processes can be connection-oriented (similar to making a phone call), an immediate point-to-point communication, or connectionless, like sending a letter through the mail. After it is sent, it might or might not arrive within a reasonable time frame, and if it gets lost, you can always send another.

Connection-oriented processes are point-to-point communication streams. These connections are thought of as virtual circuits (VCs). Each ...

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