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Osi Model Explained EssayThis paper discusses the Open System Interconnection reference position (OSI model) and the organization and function of its 7 layers. The OSI model is the most commonly referenced networking communication model, but it is rarely implemented in its entirety Ciccarelli et al. (2008). The OSI model provides a common frame of reference for discussing different hardware and software issues (Ciccarelli et al., 2008). The layers are the Application, Presentation, Session, Transport, Network, Data Link and Physical (Ciccarelli et al., 2008). When data is sent, the user employment sends data down through the layers of the model, which are self contained and constitute specific functions. Each layer adds information to the data pertaining to the layers control. The OSI model was created in 1984 by the International Standards Organization (ISO) in response to the direct for a set of standards to drop by the wayside computers to communicate through a network according to Ciccarelli et al. (2008).Additional rationales for the OSI model are given and most significant among them is that it was knowing to overcome interoperability issues with networking products from disparate vendors (Ciccarelli et al., 2008 Davis, 2008). Other reasons given for creating the OSI model include to clarify general functions of internetworking (Rivard Roherty, 2008) to divide the complexity of networking into smaller more manageable bites (Rivard Roherty, 2008) to simplify troubleshooting (Ciccarelli et al., 2008) to allow developers to change and improve components of a networking stack without altering the function of other layers (and the need to re-write them) (Rivard Roherty, 2008)A key to the understanding the OSI model is the idea of data fleeting down through the OSI model layers in one computer, then across a network media and then up through the OSI model layers in a second computer (Hill, 2002). As data flows down through the OSI model laye rs, each layer that has an applicable protocol, labels the data packet with a oral sex and a trailer specific to the layer this is known as encapsulation (Hill, 2002). On the recipient computer, the data header and trailer is removed after its values are use (or de-encapsulated) as the data packet travels up the corresponding layer of the OSI model (Ciccarelli et al., 2008 Hill, 2002). Each layer prepares the data for the adjacent layer before it is forwarded by adding header and trailer data to the data. Layer responsibilities and definitions(7) Application User programs communicate with APIs in the application layer which allows user programs to contain very little networking polity themselves (Hill, 2002). The application layer provides access to the network protocol stack. DNS brings at the application layer. Other important examples of protocols operating at this layer are http, POP3 (email protocol), SMTP (email transport protocol), IMAP (internet pass on access protocol ), FTP and Telnet includes network printing and database services. Layer devices include hosts, servers, PCs and laptops, cellular phones pic(Ciccarelli et al., 2008 Hill, 2002 Messer, 2010). (6) Presentation This layer mark offs that format of data input from the application layer is in a form suitable for transport over the network, and that it can be interpreted by the receiving node. Translates character sets such as ASCII, EBCDIC and Unicode for compatibility with far nodes. This layer compresses and encrypts data as needed pic(Ciccarelli et al., 2008 doogie966, 2011 Hill, 2002 Messer, 2010).(5) Session Sets up, maintains and breaks-down connections between network endpoint applications negotiates whether transmission will be simplex, half-duplex, or good duplex. Simplex is resembling to a broadcast in that it is one way half-duplex is two way transmission, but only one direction at a time full duplex is two-way communication at the same time using different channels to ma nage send and receive traffic pic(Ciccarelli et al., 2008 Hill, 2002 Messer, 2010 Rivard Roherty, 2008). Remote purpose calls originate from the session layer (doogie966, 2011). (4) Transport Provides reliable transport using connection-oriented services (transmission control protocol -TCP) and connection-less oriented services (user datagram protocol, or UDP). Important functions provided by this layer are flow control, error detection and error recovery. Flow control starts before data is actually sent. The transmitting node sends the receiving node a message indicating that it is about to transmit data to the receiving node.The receiving node acknowledges the receipt of the notice from the sender then data is transmitted. Flow control utilizes TCP protocol to ensure delivery of data. TCP is associated with connection-oriented service where communication is assured. Flow control also manages data transmission speed through a windowing process. A TCP window is that specific amo unt of data that can be sent before an acknowledgement is unavoidable by the receiving node. This prevents the receiving device from being overwhelmed by data pile that is cant process fast enough. Connection-less transmissions (UDP) offers no error detection or recovery mechanism and is faster without the overhead of recovery requirements pic(Ciccarelli et al., 2008 Hill, 2002 Messer, 2010 Rivard Roherty, 2008). (3) Network answerable logical addressing using IP protocol, or path determination (routing) and packet (datagrams) delivery pic(Ciccarelli et al., 2008 Hill, 2002 Messer, 2010 Rivard Roherty, 2008).When traffic arrives at the network layer, header/trailer information is added or taken away that includes the logical addressing data or IP. IP addressing allows a router to route packets to remote nodes IP. There are two ways routing can be processed one is source routing. In source routing, IP data for every router on the path to the destination is included in the data packet. The routing manner calls for the source and destination IP information to be contained within the packet. Once on the network, routers use the source and destination addresses to forward the packet to the next router, or hop, on the path to the destination (Ciccarelli et al., 2008). (2) Data Link Consists of Logical Link Control Layer and the Media Access Control Layer mackintosh layer amenable for physical addressing or for getting traffic onto the network using the MAC protocol, this layer is responsible for NIC (L1L2) control.Switches and bridges operate at this layer, since they are using the MAC physical address of the sender/receiver devices to determine which port on a switch to use, or whether to let traffic pass (bridge). Switches also operate at layers 3 and 4 pic(Ciccarelli et al., 2008 Hill, 2002 Messer, 2010). Media access control (MAC Address) addressing is managed and added/removed from traffic at this layer. Logical addresses (IP) are not considered at this layer. LLC sublayer bridges the MAC sublayer to the velocity layer protocols. 1) Physical Responsible for physical devices such as NICs(L1 2), cabling, fiber, coax, wireless, hubs, connectors (e.g. RJ-45, BNC and for implementing standards for physical configuration of connectors such as TIA/ETA (RJ-45). Also, the physical layer manages signaling and voltages required to transmit data pic(Ciccarelli et al., 2008 Hill, 2002 Martin, Not Given Messer, 2010).ReferencesCiccarelli, P., Faulkner, C., FitzGerald, J., Dennis, A., Groth, D., Skandier, T., Miller, F. (2008). Networking Basics. Hoboken, NJ John Wiley Sons, Inc. Davis, D. (2008). cisco Administration 101 Understand the OSI model to become a better Cisco troubleshooter. Retrieved 2/13/2013, 2013, from http//www.techrepublic.com/blog/networking/cisco-administration-101-understand-the-osi-model-to-become-a-better-cisco-troubleshooter/556 doogie966. (2011). OSI protocols and devices. from http//quizlet.com/6089965/osi-layer-prot ocols-devices-flash-cards/ Hill, B. (2002). Cisco The Complete Reference McGraw-Hill/Osborne Media. Martin, U. o. T. a. (Not Given). EIA/TIA 568A 568B Standard. Retrieved February 16, 2013, from http//www.utm.edu/staff/leeb/568/568.htm Messer, J. (2010). The OSI Model CompTIA Network+ N10-004 4.1. Retrieved February 14, 2013, from https//www.youtube.com/watch?feature=endscreenv=W438koUR04oNR=1 Rivard, E., Roherty, J. (2008). CCNA Flash cards Practice Pack (Third ed.) Cisco Systems, Inc.