§ TCP/IP protocols map to a four-layer conceptual model known as the DARPA model, named after the U.S. government agency that initially developed TCP/IP. The four layers of the DARPA model are: Application, Transport, Internet, and Network Interface.
§ Each layer in the DARPA model corresponds to one or more layers of the seven-layer Open Systems Interconnection (OSI) model.
§ TCP/IP means transmission control protocol and internet protocol. Protocols are set of rules which govern every possible communication over the internet.
§ These protocols describe the movement of data between the host computers or internet. These offer simple naming and addressing schemes.
§ Originally it was created to connect military networks together, later it was used by government agencies and universities.
§ It is robust to failures and flexible to diverse networks. Most widely used protocol for interconnecting computers and it is the protocol of the internet.
§ Lowest layer of the all.
§ Protocol is used to connect the host, so that the packets can be sent over it.
§ Varies host to host and network to network.
§ Selection of a packet switching network which is based on a connectionless internetwork layer is called an internet layer.
§ It the layer which holds the whole architecture together.
§ It allows the host to insert the packets.
§ It helps the packet to travel independently to the destination.
§ Order in which packets are received is different from the way they are sent.
§ IP (internet protocol) is used in this layer.
§ It decides if data transmission should be on parallel path or single path.
§ Functions such as multiplexing, segmenting or splitting on the data done by layer four that is transport layer.
§ Transport layer breaks the message (data) into small units so that they are handled more efficiently by the network layer.
§ Functions of the transport layer are same as the OSI model.
§ Transport layer also arrange the packets sent in sequence.
§ The Application layer provides applications the ability to access the services of the other layers and defines the protocols that applications use to exchange data.
§ There are many Application layer protocols and new protocols are always being developed.
§ The most widely-known Application layer protocols are those used for the exchange of user information:
§ The Hypertext Transfer Protocol (HTTP) is used to transfer files that make up the Web pages of the World Wide Web.
§ The File Transfer Protocol (FTP) is used for interactive file transfer.
§ The Simple Mail Transfer Protocol (SMTP) is used for the transfer of mail messages and attachments.
§ Telnet, a terminal emulation protocol, is used for logging on remotely to network hosts.
Advantages of TCP/IP
§ It operated independently.
§ It is scalable.
§ Client/server architecture.
§ Supports a number of routing protocols.
§ Can be used to establish a connection between two computers.
Disadvantages of TCP/IP
§ In this, the transport layer does not guarantee delivery of packets.
§ The model cannot be used in any other application.
§ Replacing protocol is not easy.
§ It has not clearly separated its services, interfaces and protocols.