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Overview Computer Network Technology

ByDiyurman Gea

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Data Networks

• Data networking solutions– Local-area networks–Wide-area networks

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Networking Devices

Equipment that connects directly to a network segment is referred to as a device.

These devices are broken up into two classifications. The first classification is end-user devices.

The second classification is network devices.

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Network Topology

Network topology defines the structure of the network. The physical topology, which is the actual layout of the wire or media, and the logical topology, which defines how the media is

accessed by the hosts for sending data.

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Network Protocols

• Protocol suites are collections of protocols that enable network communication from one host through the network to another host.

• A protocol is a formal description of a set of rules and conventions that govern a particular aspect of how devices on a network communicate.

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LAN

• Operate within a limited geographic area• Allow many users to access high-bandwidth media• Provide full-time connectivity to local services• Connect physically adjacent devices

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LAN Devices

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WAN Technologies

• Analog modems• Integrated Services Digital Network (ISDN)• Digital Subscriber Line (DSL)• Frame Relay• Asynchronous Transfer Mode (ATM)• E carrier series: E1, E3• Synchronous Digital Hierarchy (SDH)

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WAN Devices

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Metropolitan-Area Networks (MANs)

• A MAN is a network that spans a metropolitan area such as a city or suburban area.

• A MAN usually consists of two or more LANs in a common geographic area.

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Virtual Private Networks (VPNs)

A VPN is a private network that is constructed within a public network infrastructure such as the global

Internet.

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Benefits of VPNs

• A VPN is a service that offers secure, reliable connectivity over a shared public network infrastructure such as the Internet.

• VPNs maintain the same security and management policies as a private network.

• They are the most cost-effective method of establishing a point-to-point connection between remote users and an enterprise customer's network.

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VPN Types

• There are three main types of VPNs:• Intranet VPNs • Extranet VPNs • Access VPNs

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Intranets and Extranets

• Intranets are designed to permit access by users who have access privileges to the internal LAN of the organization.

• Extranets refer to applications and services that are Intranet based, but that use extended, secure access to external users or enterprises.

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OSI Reference Model

• The application (upper) layers– Layer 7: Application– Layer 6: Presentation– Layer 5: Session

• The data-flow (lower) layers– Layer 4: Transport– Layer 3: Network– Layer 2: Data link– Layer 1: Physical

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The Purpose of OSI Model

• It breaks network communication into smaller, simpler parts that are easier to develop.

• It facilitates standardization of network components to allow multiple-vendor development and support.

• It allows different types of network hardware and software to communicate with each other.

• It prevents changes in one layer from affecting the other layers so that they can develop more quickly.

• It breaks network communication into smaller parts to make learning it easier to understand.

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Why a Layered Model?

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Using Layers to for Communication

• Source, destination, and data packets– All communications originate at a source and

travel to a destination.– Information that travels on a network is referred

to as a data, packet, or data packet.

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• Media– Telephone wires (UTP)– Category 5 UTP (used for 10BASE-T Ethernet)– Coaxial cables– Optical fibers (thin glass fibers that carry light)

• Protocol – All devices on a network need to speak the

same language.– Set of rules that makes communication both

possible and more efficient.

Using Layers to for Communication

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Layers with Functions

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The Upper Layers

• Application– User interface– Examples – Telnet, HTTP

• Presentation– How data is presented– Special processing, such as encryption– Examples – ASCII, EMCDIC, JPEG

• Session– Keeping different applications’ data separate– Examples – Operating system/application access

scheduling

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The Data-Flow Layers

• Transport – Reliable or unreliable delivery– Error correction before transmit– Examples: TCP, UDP, SPX

• Network– Provide logical addressing which routers use for

path determination– Examples: IP, IPX

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• Data link– Combines bits into bytes and bytes into frames– Access to media using MAC address– Error detection not correction– Examples: 802.3/802.2

• Physical– Moves bits between devices– Specifies voltage, wire speed, and pinout cables– Examples: EIA/TIA-232, V.35

The Data-Flow Layers

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Peer-to-Peer Communication

• For data to travel from the source to the destination, each layer of the OSI model at the source must communicate with its peer layer at the destination.

• During this process, the protocols of each layer exchange information, called protocol data units (PDUs), between peer layers.

• Each layer of communication on the source computer communicates with a layer-specific PDU, and with its peer layer on the destination computer.

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The TCP/IP Reference Model

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TCP/IP Protocol Graph

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Applications

• FTP – File Transfer Protocol• HTTP – Hypertext Transfer Protocol• SMTP – Simple Mail Transfer Protocol• DNS – Domain Name System• TFTP – Trivial File Transfer Protocol

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OSI Model and TCP/IP Model

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Use of the OSI Model

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Names for Data at Each Layer

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De-Encapsulation

• When the data link layer receives the frame, it does the following:– It reads the physical address and other control

information provided by the directly connected peer data link layer.

– It strips the control information from the frame, thereby creating a datagram.

– It passes the datagram up to the next layer, following the instructions that appeared in the control portion of the frame.