The Working Principle Of Network OSI Layers

The Working Principle Of Network OSI formsA stand-alone personal electronic electronic computer means a computer having an operating system, substance abuser programs and info. It has the means to put information on a floppy diskette, on a hard disk, or on paper. Information from such a computer to passes to another user only by first taking a copy. The copy quarter be in a form of a printout or it can be information in a floppy disk, a removable hard disk, or on a compact disk.Analysis of information1. What is computer net?Acomputer network, often simply referred to as a network, is a collection ofcomputersand devices interconnect by communications channels that press forward communications among users and allows users to sh ar resources. Networks may be classified according to a wide variety of characteristics. A computer network allows sharing of resources and information among interconnected devices.2. Elements of computer networksEnddevices, also referred as hosts The sources and destinations of the communication. The devices the end users ar most familiar with. These devices act as theinterface surrounded by the end users and the underlyingnetwork. intermediator devices Devices that give network access to the attached end devices andtransportthe messages mingled with hosts. Usually it istransparentto the end users. Also, these devices accomplish communication functions in order to reassure the success of the communication process.Examples Hubs, switches, routers, modems, firewalls, etc.Transmission media The physical media thatconnectsthe devices, enabling the exchange of messages between them. It may be wired, that is, somecoppercable or opticfibercable, or wireless, that is, some radio link.ServicesNetwork, aware software acts that request network resources in order to enjoy the end user of the covering some provided service.Processes Software that runs on network devices in order to support the communication functions in accordance with the established, also in software, communication rules or protocols and help the provision of services to the end users.Messages Well-known employments. Include telephone calls, e-mail, web pages, etc.Devices and media are the physical elements or hardware of the network, whereas the services and the processes are the computer programs or software of the network.We have to note that moderncomputer networksare converged data or information networks, meaning that can carry any grammatical case of information between wide ranges of devices, and provide previously separate and distinct conventional communication methods and services, as well as new, alternative communication forms onto a common platform.3. Explanation about seven OSI social classs in clearThe OSI, or Open System Interconnection, model defines a networking framework for implementing protocols in seven tiers. tally is passed from one layer to the next, starting at the application layer in one station, and proceedin g to the bottom layer, over the channel to the next station and seat up the hierarchy. TheOSI, or Open System Interconnection, model defines a networking framework for implementing protocols in seven layers. Control is passed from one layer to the next, starting at the application layer in one station, and proceeding to the bottom layer, over the channel to the next station and back up the hierarchy.Application ( bottom 7)This layer supportsapplicationand end-user processes. conversation partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on datasyntaxare identified. Everything at this layer is application-specific. This layer provides application services forfile transfers,e-mail, and othernetworksoftwareservices.TelnetandFTPare applications that exist entirely in the application level. Tiered application architectures are part of this layer.Pre directation (Layer 6)This layer provides independence from di fferences in data representation by translating from application to network format, and vice versa. The presentation layer works to change data into the form that the application layer can accept. This layer formats and encrypts data to be sent across anetwork, providing freedom from compatibility problems. It is sometimes called the syntax layer. posing (Layer 5)This layer establishes, manages and terminates connections between applications. The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end. It deals with session and connection coordination.Transport (Layer 4)This layer provides transparent transfer of data between end systems, orhosts, and is responsible for end-to-end error recovery andflow control. It ensures complete data transfer.Network (Layer 3)This layer providesswitchingandroutingtechnologies, creating logical paths, known asvirtual circuits, for transmitting data fromnodeto node. Routing an d forwarding are functions of this layer, as well as shrouding,internetworking, error handling,congestioncontrol and packet sequencing.Data involvement (Layer 2)At this layer, data packets areencodedand decoded into bits. It furnishes transmission protocolknowledge and management and handles errors in the physical layer, flow control and frame synchronization. The data link layer is divided into two sub layers The Media Access Control layer and theLogical Link Controllayer. The MAC sub layer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls framesynchronization, flow control and error checking.Physical (Layer 1)This layer conveys the bit stream galvanising impulse, light or radio signal through thenetworkat the electrical and mechanical level. It provides thehardware means of sending and receiving data on a carrier, including defining cables, cards and physical aspects.Fast Ethernet,RS232, andATMareprotocolswith physical layer components.4. Relationship between all the layersThe OSI model originally distinguishes between service, legal separation and protocols.The transmission control protocol/IP model doesnt clearly distinguish between service, interval and protocol.The OSI model is a reference model..The TCP/IP model is an implementation of the OSI model.In OSI model, the protocols came after the model was described.In TCP/TP model, the protocols came first, and the model was really just a description of the existing protocols.In OSI model, the protocols are better hidden.In TCP/IP model, the protocols are not hidden.The OSI model has 7 layers.The TCP/IP model has only 4 layers.The OSI model supports both connectionless and connection-oriented communication in the network layer, but only connection -oriented communication in transport layer.The TCP/IP model supports both connectionless and connection-oriented communication in the transport layer, giving users the choice. rationalise all the layers with example network?Application Layer 7 It is employed in software packages which implement client-server software. When an application on one computer starts communication with another computer, then the Application layer is used. The header contains parameters that are agreed between applications. This header is often only sent at the beginning of an application operation. Examples of services within the application layer includeFTPDNSSNMPSMTP gatewaysWeb browserNetwork File System (NFS)Telnet and Remote Login (rlogin)X.400FTAMDatabase softwarePrint boniface SoftwarePresentation Layer 6 This provides function call exchange between host operating systems and software layers. It defines the format of data being sent and any encryption that may be used, and makes it presentable to the Application layer. Examples of services used are listed belowMIDIHTMLGIFTIFFJPEGASCIIEBCDICSession Layer 5 The Session layer defines how data conversations are started, controlled and fin ished. The Session layer manages the transaction sequencing and in some cases authorization. The messages may be bidirectional and there may be many of them, the session layer manages these conversations and creates notifications if some messages fail. Indications show whether a packet is in the middle of a conversation flow or at the end. Only after a completed conversation will the data is passed up to layer 6. Examples of Session layer protocols are listed belowRPCSQLNetBIOS namesAppleTalk aspDecent SCPTransport Layer 4 This layer is responsible for the ordering and reassembly of packets that may have been broken up to travel across accredited media. Some protocols in this layer also perform error recovery. After error recovery and reordering the data part is passed up to layer 5. Examples areTCPUDPSPXNetwork Layer 3 This layer is responsible for the delivery of packets end to end and implements a logical addressing scheme to help accomplish this. This can be connectionless or connection-oriented and is independent of the topology or path that the data packets travel. Routing packets through a network is also defined at this layer confident(p) a method to fragment large packets into smaller ones depending on MTUs for different media. Once the data from layer 2 has been received, layer 3 examines the destination address and if it is the address of its own end station, it passes the data after the layer 3 headers to layer 4. Examples of Layer 3 protocols includeAppletalk DDPIPIPXDECnetData Link Layer 2 This layer deals with getting data across a specific medium and individual links by providing one or more data link connections between two network entities. End points are specifically identified, if required by the Network layer Sequencing. The frames are maintained in the dress sequence and there are facilities for Flow control and Quality of Service parameters such as Throughput, Service Availability and Transit Delay. Examples includeIEEE 802.2IEEE 802 .3802.5 Token anticipateHDLCFrame RelayFDDIATMPPPThe Data link layer performs the error check using the Frame Check Sequence in the jabbing and discards the frame if an error is detected. It then looks at the addresses to see if it needs to process the rest of the frame itself or whether to pass it on to another host. The data between the header and the trailer is passed to layer 3. The MAC layer concerns itself with the access control method and determines how use of the physical transmission is controlled and provides the token ring protocols that define how a token ring operates. The LLC shields the higher level layers from concerns with the specific LAN implementation.Physical Layer 1 This layer deals with the physical aspects of the media being used to transmit the data. The electrical, mechanical, adjective and functional means this defines things like pin outs, electrical characteristics, modulation and encoding of data bits on carrier signals. It ensures bit synchronizati on and places the binary pattern that it receives into a receive buffer. Once it decodes the bit stream, the physical layer notifies the data link layer that a frame has been received and passes it up. Examples of specifications includeV.24V.35EIA/TIA-232EIA/TIA-449FDDI802.3802.5EthernetRJ45NRZNRZIConclusionTo conclude with a computer network provides connectivity between computers like autonomous systems, networks or nodes. It permits sharing of various resources among all, or several, or one of those computers that are associated with the network.