... The OSI Model: Understanding the Seven Layers of Computer Networks 1-800-COURSES www.globalknowledge.com The OSI Model: Understanding the Seven Layers of Computer Networks Paul Simoneau, Global Knowledge Course Director, Network+, CCNA, CTP Introduction The Open Systems Interconnection (OSI) model is a reference tool for understanding data communications between any two networked systems. It divides the communications processes into seven layers. Each layer both performs specific functions to support the layers above it and offers services to the layers below it. The three lowest layers focus on passing traffic through the network to an end system. The top four layers come into play in the end system to complete the process. This white paper will provide you with an understanding of each of the seven layers, including their functions and their relationships to each other. This will provide you with an overview of the network process, which can then act as a framework for understanding the details of computer networking. Since the discussion of networking often includes talk of “extra layers”, this paper will address these unofficial layers as well. Finally, this paper will draw comparisons between the theoretical OSI model and the functional TCP/IP model. Although TCP/IP has been used for network communications before the adoption of the OSI model, it supports the same functions and features in a differently layered arrangement. An Overview of the OSI Model Copyright...
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...networks together. Network models include many of protocols, such as HTTP, DHCP, IPv4, UDP and ARP, which include the rules and regulations to manage the communication between the network devices, also the limits of communication with each other (Kozierok, 2001-2005). The most commonly used are: 1. Transmission Control Protocol/Internet Protocol (TCP/IP), which established by the Defense Advanced Research Projects Agency (DARPA), and managed by the Internet Engineering Task Force (IETF), to connect the various Defense Department with each other, and uses the TCP/IP protocol to connect all governmental, educational and business institutions in the world. 2....
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...The network layer provides a mechanism called routing to achieve this. • Network layer includes services such as error control, packet sequence control and flow control. • Splits large packets into smaller ones. iv. Transport Layer This layer is concerned with functions related to the reliable and unreliable delivery of data from source to destination. Transport layer splits data into smaller packets as soon as data is sent by a computer on a network so that packets can be resent if any of them fail to reach the specified destination. The transport layer provides transparent data transfer between the end devices and controls flow of packets. This layer is responsible for ensuring complete data transfer and for the end-to-end error recovery. Transport layer transmits whole data in the predefined order and ensures flow control and error control during transmission of data from source to destination. Figure 1.2.6: Transport Layer Source: http://www.studytonight.com/computer-networks/osi-model-transport-layer Functions of Transport...
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...The OSI Model Upon trying to decide what to write about, I decided to go with The Open System Interconnection or OSI Model for short. My reasons are simple. One, the OSI Model provides a ton of information to write about. Secondly, found it to be one of the most interesting topics. My objective is to obviously explain the different layers of the OSI Model. As well as how communication occurs, and the many other functions of the Model. The OSI Reference model is based on a proposal developed by the International Standards Organization (ISO). The original objective of the OSI model was to provide a set of design standards for equipment manufactures so they could communicate with each other. The OSI model defines a hierarchical architecture that logically partitions the functions required to support system-to-system communication. “The OSI model is a theoretical representation of what happens between two nodes communicating on a network.” (Network + Guide to Networks fifth edition) It goes on say “It does not prescribe the type of hardware or software that should support each layer. Nor does it describe how software programs interact with humans.” The communication in the model is defined by its seven layers, which divides the tasks into seven smaller components that can be easily managed. A task or group of task are assigned to each layer and each layer is reasonably self- contained so that the task assigned to each layer can be managed and updated independently. My...
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...Reference Series of White Papers The OSI Model: Understanding the Seven Layers of Computer Networks 1-800-COURSES www.globalknowledge.com Pg2Pg2 The OSI Model: Understanding the Seven Layers of Computer Networks Paul Simoneau, Global Knowledge Course Director, Network+, CCNA, CTP Introduction The Open Systems Interconnection (OSI) model is a reference tool for understanding data communications between any two networked systems. It divides the communications processes into seven layers. Each layer both performs specific functions to support the layers above it and offers services to the layers below it. The three lowest layers focus on passing traffic through the network to an end system. The top four layers come into play in the end system to complete the process. This white paper will provide you with an understanding of each of the seven layers, including their functions and their relationships to each other. This will provide you with an overview of the network process, which can then act as a framework for understanding the details of computer networking. Since the discussion of networking often includes talk of “?extra layers”?, this paper will address these unofficial layers as well. Finally, this paper will draw comparisons between the theoretical OSI model and the functional TCP/IP model. Although TCP/IP has been used for network communications...
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...Describe the OSI Model and how it relates to a network. The OSI Reference Model is becoming more popular everyday because it is a useful tool for learning about networks. The OSI Reference Model is where the communication system (network) is broken down into seven layers, where each layer serves a purpose. The OSI Reference Model defines what each layer’s function is but does not specify actual services in the layers. So that the vendors can write device drivers for a device; and not be concerned about the higher layers, this speeds up the process. The seven layers are divided into three groups: 1) Application (upper) layer, 2) Intermediate layer, 3) and Network oriented (lower) layer. With this system the OSI Reference Model is convenient because you’re able to communicate with a different computer network. The WAN Network operates on the Physical and data link layer of the OSI Reference Model. What are some Protocols? The purpose of the OSI Reference Model is to determine how data should be transmitted between two points in a network. Its job is to consistently work with other products. On which layer do switches and routers operate? Layer two, three, and four the Presentation layer, Session, and Transport Layer is where the witches and routers will operate. If Routers operate on more than one layer, what is the difference? Routers operate on layer three then apply on layer two and the switch the packets. Layer two would be Ethernet and layer three is the operating...
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...OSI Model Protocol The OSI (Open Systems Interconnection) model is a logical plan that explains network interactions used by a system open to interconnection and communicate with other systems. The objective of the OSI model is to directly product implementers so that the items will frequently work with the other items. The OSI model is broken into seven layers, each of which presents a collection of services above and below it. The OSI is also of use in a training environment where a novice can use as a guide to source to understand how technologies communicate, where they reside, what functions they will perform and how protocol interacts with other protocols Briscoe, N. (2000). The primary objective of the OSI model is that the communication between the end points in networks can be separate into different levels with every level having its duties. An OSI determines how the data will flow down the seven layers at the sending end, and how it will move up through the layers at the location end of communication development. The seven layers of the OSI are the physical layer, data-link layer, network layer, transport layer, session layer, presentation layer and the application layer. A physical layer also uses bits as its PDU, which are e-signals represented in digit 1s and 0 Briscoe, N. (2000). The top four levels are used when a message is being transmitted from one user to another user. The lower three levels are practiced when a message is passing through...
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...THE OSI REFERENCE MODEL The concept of how a modern day network operates can be understood by dissecting it into seven layers. This seven layer model is known as the OSI Reference Model and defines how the vast majority of the digital networks on earth function. OSI is the acronym for Open Systems Interconnection, which was an effort formed by the International Organization for Standardization in 1982 with the goal of producing a standard reference model for the hardware and software connection of digital equipment. The important concept to realize about the OSI Reference Model is that it does not define a network standard, but rather provides guidelines for the creation of network standards. The OSI has become so accurate a concept that almost all major network standards in use today conform entirely to it's seven layer model. Though seven layers may at first appear to make a network seem overly complex, the seven layer OSI Model has been proven over the past twenty years to be the most efficient and effective way to understand this extremely complex subject. OSI LAYER 1: THE PHYSICAL LAYER The first and foundational layer of a network is the Physical Layer. The Physical Layer is literally what it's name implies: the physical infrastructure of a network. This includes the cabling or other transmission medium and the network interface hardware placed inside of computers and other devices which enable them to connect to the transmission medium. The purpose of the Physical...
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...Interconnection or OSI is a standard for computer communications that defines a networking framework for protocols that is set in seven layers. When a computer begins a transmission data is passed from one layer to the next, starting at the application layer in one computer, flowing to the bottom layer being the physical layer, over to the next computer and back up the seven layers. At one time, most vendors created their own standards to get companies to only use their computers in one form or another, because the OSI was too loosely defined so proprietary standards were the norm. Now the OSI model functionality exists in all communications systems. How Information flows through the OSI In the OSI model information is transmitted through the seven layers. The sending process passes data to the application layer. The application layer attaches a header and then passes the frame to the presentation layer. The presentation layer can transform data in different ways, by translating it and adding a header. It gives the result to the session layer. The presentation layer doesn’t know what part of the data it received from the application layer because that information is not important to the presentation layer's role. The process of adding headers is repeated from layer to layer until the frame reaches the data link layer. There, in addition to a data-link header, a data-link trailer is added this helps the synchronization of the data. The data is then passed down to the physical layer, where...
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...Material Appendix C OSI Model Key Terms Table Use the table to define the key terms related to the OSI Model. Describe the functions of any hardware connectivity devices and tools listed. . | | |Function | |Term |Definition |(if applicable) | |Physical layer |This is the first and lowest layer in the |This is when the data is sent on the | | |seven-layer OSI model. |network media by the NIC. | |Data link layer |This is layer two of the OSI model and |The Data link layer is responsible for | | |resides above the Physical Layer and below |communications between adjacent network | | |the Network Layer. |nodes. | |Network layer |The Network Layer is layer three of the OSI|The Network Layer is responsible for | | |model and resides above the Data Link Layer|establishing paths for data transfer | | |and below the Transport Layer. |through...
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...Gaddy 09/03/2014 TCP/IP Model- This model IS the internet. That is to say, this is the basis on which the internet, as we know it, was created. That isn’t saying it was the first. The Internet protocol suite(TCP/IP) was introduced in 1982 as the standard networking protocol on ARPNET. In March of 1982, the Department of Defense adopted TCP/IP as the standard for military computer networking. Layers- Compared to the Open Systems Interconnection (OSI) model, the TCP/IP model has fewer layers. It uses encapsulation to provide abstraction of protocols and services. The Application layer is at the top and is logically closer to the user. This is where applications create the user data and communicate that data to other applications. The Transport layer provides the host to host communications, creating a channel for the communication needs of the applications. The Internet layer is where the datagrams are exchanged across the network. The Link layer serves to define the networking method, and includes the protocols describing the network topology. Now, compare this with the Open Systems Interconnection (OSI) model and its seven layers, wherein each layer facilitates the needs of the layer above it, while calling on the next layer below it. This model evolved from work with ARPNET, as well. This chart shows the four layers of the TCP/IP model, showing the basic flow of information from user, via applications, to another user. I like this model for its simplicity in form and...
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...and OSI Layers TCP/IP Architecture and OSI Layers [your name here] NTC360 Network and Telecommunications Concept Associate Professor Anthony Bruno January 04, 2011 The purpose of this paper is to describe an OSI (Open Systems Interconnection) Model with details about each of the seven layers. The OSI reference model adopts a layered approach, where a communication subsystem is broken down into seven layers, each one of which performs a well-defined function. Additionally it is important to understand the purpose of the OSI model in the overall networking architecture especially as it relates to the TCP/IP (Transmission Control Protocol/Internet Protocol) Architecture, which also consists of layers each playing a particular role in the networking design. Generally speaking, the network protocol layer, which is similar to the data and network layer of the OSI model includes the protocols that allow clients and applications to send data over the network. This includes TCP/IP, NWLink (IPX/SPX), NetBEUI, Infrared Data Association (IrDA). However, the purpose of this document is to focus on the relationships between the OSI model and the TCP/IP architectures, and how they may interact together. Finally, as demonstration of this relationship a visual diagram has been provided to depicts how the TCP/IP layers correspond to the OSI model and layers. To begin with, it is important to understand the seven different layers of OSI...
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...500 WORD What is the OSI model the 7 layers The Open Systems Interconnection or (OSI model) “Is an architectural model that represents networking communication. It was introduced in 1978 by the International Organization for Standards to standardize the level of services and types of interactions for computers communicating over a network” (Emdad). The OSI is the standard that sets the path that data must travel through from one computer to another through a network. The OSI does this by the sending the through seven different layers almost like sending the data through checkpoints and at each checkpoint the data must be cleared so it is able to move on to the next stop. This is what the seven layers of OSI do. The data must go each layer, each layer performs a specific task in order to pass the data through to the next layer, and these layers also communicate to the layer above and below to make sure that everything in order. There are seven layers and each one has a specific function that prepares it for next layer the data must pass through all seven layers. The layers are separated into two sets the first is the application set • Application layer 7- This is the layer that provides the interface between the network protocol and the software running on the computer. This layer handles anything that communicates with the internet; this layer also handles any network related activity such as file transfers or reading and sending email. This layer is the closest one to...
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...The OSI and TCP/IP The OSI model is an important part of providing network services over the Internet. This paper describes the seven different levels of the OSI model and the TCP/IP stack. Also, this paper will compare and contrast the main protocols being TCP and IP and the functions of each protocol. Also, this paper will discuss as to why the OSI model is important and why we still need the OSI model in today’s technological age of information exchange. Application Layer The Application Layer is number seven of the OSI model, which provides user interfaces that end-users are able to understand and interact through services, such as E-mail, FTP, Telnet, instant messaging software, IRC and DNS applications (Petri, 2009). Presentation Layer The Presentation Layer is number six of the OSI model, and it responds to the service requests of the application layer and sends requests to the session layer. Specific functions of the presentation layer are as follows: • Translates data from applications into local machine formats the computer can understand and vice-versa for the end-user. • Communicates with the applications layer. • Communicates with the session layer (Petri, 2009). Session Layer The Session Layer is number five of the OSI model, and it keeps track of connections. The session layer keeps track of multiple file downloads requested by a particular FTP application, or Telnet connections, or web page retrievals from a particular server (Petri...
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...continue to use IPX/SPX. * NetBEUI: NetBIOS Extended User Interface is a protocol used primarily on small Windows NT networks. NetBEUI cannot be routed or used by routers to talk to each other on a large network. NetBEUI is suitable for small peer-to-peer networks, involving a few computers directly connected to each other. It can be used in conjunction with another routable protocol such as TCP/IP. This gives the network administrator the advantages of the high performance of NetBEUI within the local network and the ability to communicate beyond the LAN over TCP/IP. * AppleTalk: AppleTalk is a protocol suite to network Macintosh computers. It is composed of a comprehensive set of protocols that span the seven layers of the Open Systems Interconnection (OSI) reference model. The AppleTalk protocol was designed to run over LocalTalk, which is the Apple LAN physical topology. This protocol is also designed to run over major LAN types, notably Ethernet and Token Ring. * HTTP: Hypertext Transfer Protocol governs how files such as text, graphics, sound, and video are exchanged on the World Wide Web (WWW). The Internet Engineering Task Force (IETF) developed the standards for HTTP. * FTP: File Transfer Protocol provides services for file transfer and manipulation....
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