OSI Model Layer : A complete Explaination


Open Systems Interconnection LAYERS

The open Systems Interconnection model (OSI) is a conceptual model that standardizes and characterizes the internal functions of a communication system by partitioning it into abstraction layers. The model is a product of the Open systems Interconnection project at the International Organization for Standardization (ISO).

The OSI reference model has seven layers. These were decided on the basis of following principles:

  • A layer should be created where a different level of abstraction is needed.
  • Each layer should perform a well-defined function
  • The laser boundaries should be chosen to minimize the information flow across the interface.

OSI model itself is not a network architecture. It does not specify the exact services and protocols to be used in each layer. It just tell what each laser should do. It provides a basis for coordinating the development of a standard that would facilitate a flexible interconnection of systems.

The seven layers of OSI model are:

  • Physical layer
  • Data link layer
  • Network layer
  • Transport layer
  • Session layer
  • Presentation layer
  • Application layer
1PhysicalTransmits data over physical mediumMultiplexer and repeater, hub, Amplifier, OscilloscopeIEEE802, IEEE802.2, ISO2110, ISDN
2Data linkPackages raw bits into frames and includes a cyclical redundancy check (CRC)Switch, bridge and brouter, NICLIC
3NetworkHandles addressing, translates logical addresses and names to physical addresses, routing and traffic managementRouter and BrouterIP, IPX, NW Link, NetBEUL
4TransportRepackages messages into smaller formats, provides error free delivers and error handling functionsGatewayNetBEUI, TCP, SPX and NW Link, ARP, RARP, NETBios
5SessionAllows two applications to communicate over a network by opening a session and synchronizing the involved computersGatewayNetBios, RPC
6PresentationPerforms protocols conversion, encryption and data compressionGateway and redirectorsAFP, TDI, SMB, NCP
7ApplicationProvides network access for applications, flow control and error recoveryGatewaySMTP, ETP, SNMP, Telnet, Appletalk, DNS,TFTP, MINE, LOGIN, NFS, BOOTP

Important Questions for IT Officer

(Visited 1,831 time, 1 visit today)