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Introduction TCP/IP Reference Model What is a protocol? Why was TCP/IP invented ? Layers of TCP/IP Reference Model eITnotes.com

TCP/IP Reference Model TCP/IP is a set of protocols developed to allow cooperating computers to share resources across a network. TCP/IP reference model forms the base of present day Internet. TCP stands for “Transmission Control Protocol”. IP stands for “Internet Protocol”. eITnotes.com

Why was TCP/IP invented ? ARPANET (Advanced Research Project Agency Network) was first network sponsored by U.S. department of defense. It connects many universities and govt. installation using leased telephone lines. Later on when the satellites and radio networks were added to ARPANET, the existing protocols were not able to handle such a network. Therefore a new model called TCP/IP reference model was introduced. eITnotes.com

The TCP/IP Model defined in 1974 for the first time. The main goal of TCP/IP was to build an interconnection of networks, referred to as an internetwork, or internet, that provided universal communication services over heterogeneous physical networks. The clear benefit of such an internetwork is the enabling of communication between hosts on different networks, perhaps separated by a large geographical area. Why was TCP/IP invented ? eITnotes.com

What is a protocol? A protocol is a collection of rules and procedures for two computers to exchange information. Protocol also defines the format of data that is being exchanged. eITnotes.com

Layers of TCP/IP Reference Model Network Interface Layer Internet Layer Transport Layer Application Layer eITnotes.com

Network Interface Layer It is the bottom layer of TCP/IP model and lies above the internet layer. It also called the link layer, because it provides interface to the actual network hardware. This interface provide reliable delivery, and may be packet or stream oriented. It includes wires, network interface cards, etc. Other related details within this layer are connectors, signal strength, and wavelength along with various others. contd… eITnotes.com

It will use the required LAN operating algorithm, such a CMSA/CD(Carrier sense Multiple Access with Collision Detect) or Token Ring Passing and responsible for placing data within frame. The frame format is dependent on the system being used. The frame holds the h/w address of the host,data and checking algos for data integrity. contd… eITnotes.com

Network Interface Layer Protocols ATM : used to transfer packets of fixed size i.e. 53 bytes cell with 600 mbps speed. FDDI(Fiber Distributed Data Interface): data transmission on fiber lines upto 2km with 200 mbps speed. Ethernet: is standard communication protocol for building LAN. It creates communication system that allows sharing of data and resources. eITnotes.com

Internet Layer It is the second layer of TCP/IP and lies b/w Network Interface Layer and Transport Layer. The network layer, provides the “virtual network” image of an internet. Internet Protocol (IP) is the most important protocol in this layer. It is a connectionless protocol that does not assume reliability. IP provides a routing function that attempts to transmit messages to their destination. contd... eITnotes.com

Different packets are routed independently. So the order n which packets arrive at destination can be different from the order in which they were sent. In such case it is the responsibility of the higher layer to arrange these packets. It also provides congestion control. contd… eITnotes.com

A message unit in an IP network is called an IP datagram. This is the basic unit of information transmitted across TCP/IP networks. Other network-layer protocols are ICMP, IGMP, ARP etc. contd… eITnotes.com

Internet Layer Protocols ARP (Address Resolution Protocol) – Resolves IP addresses to the corresponding MAC level h/w address by for instance broadcasting. ICMP (Internet Control Message Protocol) –Diagnostics and error reporting (IGMP) Internet Group Management Protocol –Management of group multicast eITnotes.com

Transport Layer It is the third layer of TCP/IP and lies b/w Internet Layer and Application Layer. This layer acts as a delivery service used by the application layer. It also use checksum, acknowledgement and time outs to control the transmission. It provides the end-to-end data transfer by delivering data from an application to its remote system. contd… eITnotes.com

Transport Layer Protocols Transmission Control Protocol (TCP) which provides connection-oriented reliable data delivery, congestion control, and flow control. User Datagram Protocol (UDP) Provides connectionless, unreliable, service. UDP is used by applications that need a fast transport mechanism and can tolerate the loss of some data. Used for the transmission of small amount of data.E.g video and audio casting eITnotes.com

Application Layer It lies above the transport layer. Application Layer helps people and machines to communicate. It handles the details of the particular application. An application is a user process cooperating with another process. It provide services to various user applications like file transfer, , remote login, fetching web pages etc. eITnotes.com

Protocols used in Application Layer Sr. No.ProtocolFull FormPurpose 1.TELNETTerminal NetworkFor remote login 2.SMTPSimple Mail transfer Protocol For 3.FTPFile Transfer ProtocolFor transferring files 4.DNSDomain Name ServerFor mapping host names into network address 5.HTTPHyper Text Transfer Protocol For fetching wed pages 6.NNTPNetwork News Transfer protocol For moving news articles 7.POP3Post Office Protocol 3For incoming mail eITnotes.com

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