Osi Model In Data Communication And Networking Pdf

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The OSI Model is a logical and conceptual model that defines network communication used by systems open to interconnection and communication with other systems.

For IT professionals, the seven layers refer to the Open Systems Interconnection OSI model, a conceptual framework that describes the functions of a networking or telecommunication system. The model uses layers to help give a visual description of what is going on with a particular networking system.

Chapter 2: Protocol

A protocol is a set of rules that governs the communications between computers on a network. In order for two computers to talk to each other, they must be speaking the same language. Many different types of network protocols and standards are required to ensure that your computer no matter which operating system, network card, or application you are using can communicate with another computer located on the next desk or half-way around the world.

The complexity of these layers is beyond the scope of this tutorial; however, they can be simplified into four layers to help identify some of the protocols with which you should be familiar see fig 1. Figure 1 illustrates how some of the major protocols would correlate to the OSI model in order to communicate via the Internet. In this model, there are four layers, including:. The physical layer of the network focuses on hardware elements, such as cables, repeaters, and network interface cards.

By far the most common protocol used at the physical layer is Ethernet. For example, an Ethernet network such as 10BaseT or BaseTX specifies the type of cables that can be used, the optimal topology star vs. See the Cabling section for more information on Ethernet standards related to the physical layer. The data link layer of the network addresses the way that data packets are sent from one node to another.

This is a system where each computer listens to the cable before sending anything through the network. If the network is clear, the computer will transmit. If some other node is already transmitting on the cable, the computer will wait and try again when the line is clear. Sometimes, two computers attempt to transmit at the same instant.

When this happens a collision occurs. Each computer then backs off and waits a random amount of time before attempting to retransmit. With this access method, it is normal to have collisions. However, the delay caused by collisions and retransmitting is very small and does not normally effect the speed of transmission on the network. The original Ethernet standard was developed in and had a maximum speed of 10 Mbps phenomenal at the time over coaxial cable. The Ethernet protocol allows for bus, star, or tree topologies, depending on the type of cables used and other factors.

This heavy coaxial cabling was expensive to purchase, install, and maintain, and very difficult to retrofit into existing facilities. The current standards are now built around the use of twisted pair wire. Fiber cable can also be used at this level in 10BaseFL. The Fast Ethernet protocol supports transmission up to Mbps. In addition, category 5 twisted pair or fiber optic cable is necessary. Fast Ethernet standards include:.

Gigabit Ethernet standard is a protocol that has a transmission speed of 1 Gbps Mbps. It can be used with both fiber optic cabling and copper.

The Ethernet standards continue to evolve. Several very popular network protocols, commonly used in the 90's and early 21st century have now largely fallen into disuse. While you may hear terms from time to time, such as "Localtalk" Apple or "Token Ring" IBM , you will rarely find these systems still in operation. Although they played an important role in the evolution of networking, their performance and capacity limitations have relegated them to the past, in the wake of the standardization of Ethernet driven by the success of the Internet.

The network layer is in charge of routing network messages data from one computer to another. Every network device such as network interface cards and printers have a physical address called a MAC Media Access Control address. When you purchase a network card, the MAC address is fixed and cannot be changed. Networks using the IP and IPX protocols assign logical addresses which are made up of the MAC address and the network address to the devices on the network, This can all become quite complex -- suffice it to say that the network layer takes care of assigning the correct addresses via IP or IPX and then uses routers to send the data packets to other networks.

The transport layer is concerned with efficient and reliable transportation of the data packets from one network to another.

In most cases, a document, e-mail message or other piece of information is not sent as one unit. Instead, it is broken into small data packets, each with header information that identifies its correct sequence and document.

When the data packets are sent over a network, they may or may not take the same route -- it doesn't matter. At the receiving end, the data packets are re-assembled into the proper order.

After all packets are received, a message goes back to the originating network. If a packet does not arrive, a message to "re-send" is sent back to the originating network. TCP, paired with IP, is by far the most popular protocol at the transport level. Several protocols overlap the session, presentation, and application layers of networks.

There protocols listed below are a few of the more well-known:. Florida Center for Instructional Technology. College of Education ,. University of South Florida ,. This publication was produced under a grant from the Florida Department of Education. The information contained in this document is based on information available at the time of publication and is subject to change. Although every reasonable effort has been made to include accurate information, the Florida Center for Instructional Technology makes no warranty of claims as to the accuracy, completeness, or fitness for any particular purpose of the information provided herein.

Nothing herein shall be construed as a recommendation to use any product or service in violation of existing patents or rights of third parties. What is a Protocol? OSI model related to common network protocols Figure 1 illustrates how some of the major protocols would correlate to the OSI model in order to communicate via the Internet.

Ethernet The original Ethernet standard was developed in and had a maximum speed of 10 Mbps phenomenal at the time over coaxial cable.

Gigabit Ethernet Gigabit Ethernet standard is a protocol that has a transmission speed of 1 Gbps Mbps. TCP and SPX Transport Layer The transport layer is concerned with efficient and reliable transportation of the data packets from one network to another.

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The OSI Model: Overview on the Seven Layers of Computer Networks

Here are the basic functionalities of the Session layer: The Presentation layer is also called as the layer 6 of the OSI model. OSI Model. The Open Systems Interconnection OSI model defines a networking framework to implement protocols in layers, with control passed from one layer to the next. In plain English, the OSI model helped standardize the way computer systems send information to each other. Data encapsulation is also done at this layer. By using our site, you agree to our collection of information through the use of cookies. OSI stands for Open System Interconnection is a reference model that describes how information from a software application in one computer moves through a physical medium to the software application in another computer.

A protocol is a set of rules that governs the communications between computers on a network. In order for two computers to talk to each other, they must be speaking the same language. Many different types of network protocols and standards are required to ensure that your computer no matter which operating system, network card, or application you are using can communicate with another computer located on the next desk or half-way around the world. The complexity of these layers is beyond the scope of this tutorial; however, they can be simplified into four layers to help identify some of the protocols with which you should be familiar see fig 1. Figure 1 illustrates how some of the major protocols would correlate to the OSI model in order to communicate via the Internet.

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Layers of OSI Model Explained

There are n numbers of users who use computer network and are located over the world. So to ensure, national and worldwide data communication, systems must be developed which are compatible to communicate with each other ISO has developed a standard. ISO stands for International organization of Standardization.

The Open Systems Interconnection OSI model describes seven layers that computer systems use to communicate over a network. It was the first standard model for network communications, adopted by all major computer and telecommunication companies in the early s. However, the OSI 7-layer model is still widely used, as it helps visualize and communicate how networks operate, and helps isolate and troubleshoot networking problems.

The OSI Model is a logical and conceptual model that defines network communication used by systems open to interconnection and communication with other systems. The Open System Interconnection OSI Model also defines a logical network and effectively describes computer packet transfer by using various layers of protocols. What is OSI Model?

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The OSI Model - Features, Principles and Layers

Он хотел прикоснуться к ней, но не посмел. Услышав имя Дэвида, произнесенное вслух, Сьюзан дала волю своему горю. Сначала она едва заметно вздрогнула, словно от озноба, и тут же ее захлестнула волна отчаяния. Приоткрыв дрожащие губы, она попыталась что-то сказать, но слов не последовало. Не спуская со Стратмора ледяного взгляда, Сьюзан сделала шаг вперед и протянула к нему руку с зажатым в ней предметом. Стратмор был почти уверен, что в руке Сьюзан сжимала беретту, нацеленную ему в живот, но пистолет лежал на полу, стиснутый в пальцах Хейла. Предмет, который она держала, был гораздо меньшего размера.

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 Он немного сонный, мадам. Дайте ему минутку прийти в. - Н-но… - Сьюзан произнесла слова медленно.  - Я видела сообщение… в нем говорилось… Смит кивнул: - Мы тоже прочитали это сообщение. Халохот рано принялся считать цыплят. - Но кровь… - Поверхностная царапина, мадам.

Layer 6 - Presentation

Католицизм здесь посильнее, чем в самом Ватикане. - У нас, конечно, не все его тело, - добавил лейтенант.  - Solo el escroto. Беккер даже прервал свое занятие и посмотрел на лейтенанта. Solo el escroto. Он с трудом сдержал улыбку.

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 Ja, - признался он. - Вам известно, что в Испании это противозаконно. - Nein, - солгал немец.  - Я не. Я сейчас же отправлю ее домой.

К рабочему кабинету Стратмора, именуемому аквариумом из-за стеклянных стен, вела узкая лестница, поднимавшаяся по задней стене шифровалки. Взбираясь по решетчатым ступенькам, Сьюзан смотрела на массивную дубовую дверь кабинета, украшенную эмблемой АНБ, на которой был изображен могучий орел, терзающий когтями старинную отмычку. За этой дверью находился один из самых великих людей, которых ей довелось знать. Пятидесятишестилетний коммандер Стратмор, заместитель оперативного директора АНБ, был для нее почти как отец.

Layers of OSI Model Explained

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