What is OSI Layer Model

OSI Layer Model is a creation defined by international organization for standards and OSI stands for Open Systems Interconnection. This method split communication system into seven different layers. A layer is an assortment of theoretically comparable functions that offer services to the layer over it and obtains services from the layer below it. OSI Layer Model facilitates the user a blunder free transportation transversely a network and offer the pathway required by applications. The layers throw and obtain packets that provide the path to contents. OSI Layer Model offering a framework for networking which employ protocols in seven layers. The processing control exceed from one layer to next layer and this process continue till the end .The processing start from bottom layer and then over the channel to further station and backing the hierarchy. The OSI model layer consists of seven layers and each layer interacts with each other. The layer one and two called media layer and layer 3, 4, 5, 6, and 7 called host layers. OSI layer model is classified into 7 categories discussed in detail under.

  1. OSI Physical Layer
  2. OSI Data Link Layer
  3. OSI Network Layer
  4. OSI Transport Layer
  5. OSI Session Layer
  6. OSI Presentation Layer
  7. OSI Application Layer


OSI Physical Layer

OSI Physical Layer is responsible for media, signal and binary communications. OSI Physical Layer describes the physical and electrical stipulations for devices in depth it identify the relationship among physical medium and devices such as bus adopters, repeaters, hubs, cables, pins, voltages and network adapters etc. The functionality of OSI Physical Layer contrast with the OSI Data Link Layer as physical layer is a primarily with the communication of a particular device with a standard while data link layer deals at last two or multiple devices. OSI Physical layer contains cables, cards, and various physical features for data carrier such as protocol, ATM, RS232, and Ethernet. OSI Physical layer perform following functions or services. Physical layer is responsible to set up and terminate a link to a communication medium. Physical layer play a part where the communication resources are efficiently shared between manifold users. Physical layer offer hardware resources for sending and receiving of data. It also handled the exchanging between the demonstrations of digital data and signals broadcasting over a transportation channel such as optical fiber, copper wire, and over a radio link SCSI buses also operated in this layer.


OSI Data Link Layer

OSI Data Link Layer provides Physical addressing. OSI Data Link Layer gives procedural and functional resources for broadcasting of data among networks. It also identifies errors of physical layer and tries to correct them. The main propose of OSI Data link layer propose is to handled point to multi point and point to point media. The encoded and decoded of data into bits is the main functionality of OSI Data Link Layer including frames management and flow control. OSI Data Link Layer has two sub layers Media Access Control (MAC) layer which is responsible to manage how and where computers on the network get access to the information and consent to broadcast it and OSI Logical Link Control (LLC) layer control which is responsible for frame management, error checking, and flow control of data. The HDLC, LSL, and ATM are the implemented protocols on his layer.


OSI Network Layer

OSI Network Layer is used for logical addressing as virtual circuits which are used to transmit data from node to node and determination of Path. OSI Network Layer is also offering routing and switching technologies. The error handling, packet sequencing, internetworking, addressing, and congestion control are the main functionality of Network layer. It also provides best quality of service on the request of transport layer. The IPX and TCP/IP are the implemented protocols on this layer. Network Layer has three sub layers as listed below.

Subnetwork Access: Subnetwork Access regard as protocols and responsible to deal with interface to network as X.25.

Subnetwork Dependent Convergence: It is responsible to carry level of transportation network up to the level of network on any side.

Subnetwork Independent Convergence: It is used to manage transformation across multiple networks.


OSI Transport Layer

OSI Transport Layer provides connections from end-to-end, flow control of data, and reliability of transmit data. It is also offering error recovery. OSI Transport Layer can maintain path of the section and resend those that fail. The most common example of Transport layer is Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). The working of OSI Transport Layer is just like a post office which deals lots of mail, dispatches and sending of parcel while in post office outer envelop of mail used but in Transport layer double envelop used as cryptographic presentation services that can be read only by addresses. The tunneling protocols operated by Transport layer. The SPX, TCP/IP’s, DNS are examples of implemented protocols on this layer.


OSI Session Layer

OSI Session Layer deals with Inter-host communication. It is responsible to manage, establish and conclude the link among applications. Through OSI Session layer the setting up of new connection can be handled, if needed conversation terminated, and exchanging of dialogue between the applications at every end. OSI Session Layer also administers session and link coordination. It also offers full and half duplex including simple operation. The OSI Session Layer is generally executed explicitly in application surroundings that employ remote system calls. The SAP, and TCP/IP remote procedure call are the examples of implemented protocols.


OSI Presentation Layer

OSI Presentation Layer is providing data representation, convert plain text into code as encryption and decoding of data. OSI Presentation Layer offering liberty from compatibility troubles therefore it is also called syntax layer. It also set up a perspective among application layer entities. OSI Presentation Layer decoded data demonstration from application to network format and vice versa. It has essential encoding rules of ANSI which have ability to changing an EBCDIC-coded text file to an ASCII-coded file. Data translation, Data conversion and compression are the main task of OSI Presentation Layer. The NCP and Apple talk Filing Protocol are implemented in presentation layer.


OSI Application Layer

OSI Application Layer is responsible for network process to application. It supports various types of applications and end user procedures. OSI Application Layer identifies the communication associate, Excellency of service, user verification, privacy, and restraint of data syntax. Application Layer also offering various services such as file transformation, e-mail, and network software services. It contains Telnet and FTP and also includes Tiered application architectures. The well known examples of OSI model layers are web browsing, SAP, SMTP, TCP/IP, and NFS.