§  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.

Host-to-network Layer:

§  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.

Internet layer:

§  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.

Transport 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.

Transport Layer:

§  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.


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