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OSI Model: Using Open Systems Interconnection to Send and Receive Data

OSI model stands for Open System Interconnection Model is considered as reference model so that applications can communicate over a network. This model is maintained by International Organization for standardization(ISO). The purpose of this conceptual framework is to understand the relation among application and build it. Main functionality supported by this model is interoperability between vendors so that the software programs create by developers will interoperate. This model reduce complexity by breaking down into several components of 7 layers. It standardize interface by allowing multiple vendors to develop and support. If you change is one layer it doesn’t affect another layer this will go for quick development. Developer can rewrite the entire protocol in any layer this will provide effective update and improvement to any component.

OSI Model Layers

Layer 1: Physical layer

This is the lowest layer of the OSI model which is concerned with the transmission of bits over physical medium. Main purpose of this layer to carry the signals, electrical impulses and radio signals to the upper layer in the model. Examples of Physical layer Protocol Fast Ethernet, RS232 with the layer components.

Layer 2: Data-link layer

This is the second layer. Primary purpose of this layer is to transfer data between adjacent layers. Function of this layer to establish a link across physical network and putting packets of bits that come from physical layer into network frames so that they can travel to the next upper layer. This layer divided into two sub link layer logical link layer and media access control. Function of MAC layer is to check how a computer on network can access data and transmit it and function of LLC layer to make sure frame should travel in synchronized way to the network layer, control the flow of data, and check error and handle them comes from physical layer. Example of Data-link layer protocol PPP(Point-to-point protocol), Ethernet for LAN and many more.

Layer 3: Network layer

This layer transmit data from node to node by providing some of the technologies like addressing and routing through logical/virtual circuits. It also control the congestion and follow packet sequencing to transfer data. Protocol used by this layer is IP (Internet Protocol), RIP (Routing Information Protocol), ICPM (Internet Control Message protocol).

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Layer 4: Transport layer

This layer manage the delivery of packets including checking for errors once the data is arrived. This layer is also responsible for end-to-end data recovery, message delivery with acknowledgment and ensure to complete data transfer to the end point. This tells transmitting station to back-off when no buffer available to avoid message traffic control. Protocol used by this layer TCP, UDP and many more.

Layer 5: Session layer

Function of this layer is to establish, manage and terminate the connection between applications when they are transferring data. This layer authenticate the application before connecting to another one and reconnect them if the interruption comes. Application of this layer is web conferencing, live TV. Protocol used in this layer SCP, X.225, SMPP and so on.

Layer 6: Presentation layer

Primary function of this layer is to convert incoming and outgoing data from one form to another and present it to the Application layer. Basically it convert one network format into another required one. Layer encrypts data to be sent across a network freedom from compatibility to the change in platform. Protocol used by this layer NCP, ICA, AFP and so on.

Layer 7: Application layer

This the top most layer in the OSI model which interact with the user and user application. Layer is for application involved in communication system, and Communication partners are identified. Protocol used by this layer DND, FTP, HTTP, DHCP and many more.

OSI Model 7 layers