IP, the Internet protocol，was designed to allow multiple routes between any two points and to route packets of data around damaged routers.


TCP was layered on top of IP to give each end of a connection the ability to acknowledge receipt of IP packets and request retransmission of lost or corrupted packets. Furthermore, TCP allows the packets to be put back together on the receiving end in the same order they were sent.


 UDP is an unreliable protocol that does not guarantee that packets will arrive at their destination or that they will arrive in the same order they were sent

 ICMP, the Internet Control Message Protocol, which uses raw IP datagrams to relay error messages between hosts.


 The part of the host-to-network layer made up of the hardware that connects different computers (wires, fiber optic cables, microwave relays, or smoke signals) is sometimes called the physical layer of the network. .


A network layer protocol defines how bits and bytes of data are organized into the larger groups called packets, and the addressing scheme by which different machines find each other.


The transport layer is responsible for ensuring that packets are received in the order they were sent and making sure that no data is lost or corrupted The layer that delivers data to the user is called the application layer,The application layer decides what to do with the data after it's transferred.

The three lower layers all work together to define how data is transferred from one computer to another.

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