TCP/IP reference model

After the introduction of satellites and radio networks, researchers started working on a modified reference model since OSI reference model was not competent. This resulted in the development of TCP/IP reference model.  The four major layers used in this model are the internet layer, transport layer, application layer and host-to-network layer. The internet layer holds the whole architecture together and is a connectionless layer. It permits hosts to inject switching packets into any network and any destination. This packet format is an official format referred as IP, the Internet Protocol. The transport layer is a layer above the internet layer which allows peer entities on the source and destination hosts to carry on a conversation. There are two varieties of transport protocols- transmission control protocol and user datagram protocol. Application layer lie at the top of transport layer. All the higher-level protocols are incorporated in it. TELNET, FTP, SMTP, DNS, NNTP, USENET etc. are examples. The host-to network layer which lies below the internet layer is the choice of user/host through which user attempts connection to the network. TCP/IP reference model fails to distinguish concepts like service, interface and protocol. TCP/IP model fails in Bluetooth related devices and technology.