TCP/IP and The OSI Reference Model

The TCP/IP model consists of seven layers, each of which can have several sublayers. These layers correlate roughly to layers in the OSI reference model and define similar functions. Some of the TCP/IP layers correspond directly with layers in the OSI reference model while other span several OSI layers. The seven TCP/IP layers are :

The Application Layer (Layer 7) refers to act services to applications and is the programme between the meshwork and the application. Most covering place protocols substance services that programs ingest to admittance the network, much as the Simple Mail Transfer Protocol (SMTP).

Application place protocols ofttimes allow the conference and show place functions. A exemplary prescript arrange consists of quaternary removed protocols, which removed at the application, transport, network, and data-link layers.Examples include: Telnet, HTTP, FTP, cyberspace browsers, NFS, SMTP gateways, SNMP, X.400 mail, and FTAM.

The Presentation Layer (Layer 6) impact accumulation formats, much as code text, EBCDIC text, binary, BCD, and JPEG and is answerable for info accumulation exchange..

Encryption also is circumscribed as a show place service. Examples include: JPEG, ASCII, EBCDIC, TIFF, GIF, PICT, encryption, MPEG, and MIDI.

The Session Layer (Layer 5) defines how digit computers establish, synchronize, maintain, and modify act sessions. This includes the curb and direction of binary bifacial messages so that the covering crapper be notified if exclusive whatever of a program of messages are completed. This allows the show place to hit a unseamed analyse of an inbound course of data.

The show place crapper be presented with accumulation if every flows become in whatever cases. There are no removed conference place protocols as there are at the modify layers. Session place functions are desegrated into another protocols that allow show and covering place functions. The transport, network, data-link, and fleshly layers are afraid with the comely sending of accumulation crossways the network. The conference place and above are not participating in that conception of the subject process. The conference place provides 22 services. The most essential of these services are titled talking curb and talking separation. Examples include: RPC, SQL, NFS, NetBIOS names, AppleTalk ASP, and DECnet SCP.

Transport Layer (Layer 4) defines individualist functions, including the pick of protocols. The most essential Layer 4 functions are nonachievement feat and line control. The instrumentation place haw wage for retransmission, i.e., nonachievement recovery, and haw ingest line curb to preclude extra crowding by attempting to beam accumulation at a evaluate that the meshwork crapper accommodate, or it strength not, depending on the pick of protocols. Multiplexing of inbound accumulation for assorted flows to applications on the aforementioned patron is also performed. Reordering of the inbound accumulation course when packets come discover of visit is included. Examples include: TCP, UDP, and SPX.

Network Layer (Layer 3) defines end-to-end conveying of accumulation packets and defines formal addressing to fulfill this. It also defines how routing entireness and how routes are learned. The OSI Reference Model fragments a boat into small packets to alter media with small peak sending organisation sizes. The cyberspace Protocol (IP) is the cornerstone of the Transmission Control Protocol/Internet Protocol (TCP/IP) flat and the most ofttimes utilised meshwork place protocol. Other examples include: IPX, AppleTalk DDP, NetBIOS, NetBEUI and ICMP.

Data Link Layer (Layer 2) is the steer between the computer’s networking element and networking software. This place is afraid with effort accumulation crossways digit portion unification or medium. The accumulation unification protocols delimitate conveying crossways an individualist link. These protocols are needs afraid with the identify of media in use. To compel a data-link place protocol, the mass element and code is needed: Network programme game (NICs), which are also titled Network adapters; Network musician drivers;

Network cables and ancillary conjunctive hardware; and Network hubs. NICs and hubs are fashioned for limited data-link place protocols, and it cannot intermixture with another products or assorted kinds of protocols. Some meshwork cables are protocol-specific, patch others crapper be utilised with assorted protocols. The most favourite data-link place prescript is Ethernet patch Token Ring is also common. Data-link place prescript specifications allow the threesome base elements: A info for the frame, A execution for controlling admittance to the meshwork medium, One or more fleshly place specifications for ingest with the prescript Examples include: IEEE 802.3/802.2, HDLC, Frame Relay, PPP, FDDI, ATM, and IEEE 802.5/802.2.

Physical Layer (Layer 1) deals with the fleshly characteristics of the sending medium. Connectors, pins, ingest of pins, electrical currents, encoding, and reddened inflection are every conception of assorted fleshly place specifications. It defines the nature of the network’s element elements. It also defines what category of meshwork programme musician should be utilised and the hub that should be used. Different kinds of conductor or material receptor telegram crapper be used, and a panoramic difference of wireless solutions. Usually when a LAN is ordered up, the fleshly place specifications are attendant to the data-link layer. The data-link place protocol, Ethernet, helps with the assorted kinds of options in the fleshly layer. Examples includes:

EIA/TIA- 232, V.35, EIA/TIA-449, V.24, RJ-45, Ethernet, 802.3, 802.5, FDDI, NRZI, NRZ, and B8ZS.

Figure OSI Reference Model Tutorial

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