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WHY NEED NETWORKING?

- Access to remote information- Person-to-person communication- Cooperative work online- Resource sharing

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NETWORKING1) Communication methodology and protocols:rules and conventions to be followed for the communicating systems to “understand” each other

2) Topology and design:The layout of the network

3) Addressing:How systems locate each other on the network

4) Routing:How the data path is established

5) Reliability:Making sure the received data are exactly what have been sent.

6) Interoperability:The degree to which products of different companies can network with each other

7) Security:Protection of all components of a network

8) Standards.

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A NETWORK comprises of:

1- PROTOCOL SOFTWARE: - encodes and formats data - detects and corrects problems

2- TRANSMISSION HARDWARE: - cables - satellites

3- SPECIAL-PURPOSE HARDWARE DEVICES:- Interconnect transmission media- Transmission control

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POINT-TO-POINT COMPUTER TOPOLOGIES

STAR RING

BUS

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NETWORKS AND LAYERS

Networks are organized as series of LAYERS

Each layer is built on the one below it

The purpose of each layer is to offer services to the other layer

The number and function of layers may vary among different networks.

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COMMUNICATIONS PROTOCOLCommunications protocols are rules established to govern the way data are transmitted in a computer network.

THE PHYSICAL LAYER – Defines the manner in which nodes of a network are connected to one another

SUBSEQUENT LAYERS – describe how messages are packaged for transmission

- how messages are routed through the network - security procedures - the manner in which messages are displayed

Example known: TCP/IP (Transmission control protocol/ Internet protocol)

Application

Transport

Network

Data Link

Physical

5 Layers of TCP/IP

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LOCAL AREA NETWORKS

Valuable resources can be shared by all computers networked in LAN:

- Applications software- Links to other LAN servers- Communication capabilities (lines or modem)- I/O devices (printers, scanners etc)- Storage devices- Add-on boards (video capture board etc)

TYPES OF NETWORKS1. Wide Area Network (WAN)

2. Metropolitan Area Network (MAN)

3. Local area Network (LAN):connects nodes in close proximity

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LAN ACCESS METHODS

1) TOKEN ACCESS METHOD:an electronic “token” travels around a ring of nodesheader specifies whether the token is “free” or carrying signals

a sender node captures a free token and changes it to “busy”

2) ETHERNET:Nodes must contend for the right to send message.Node requests network service from the network softwareThe request might return a “busy” signal or a “line free” signal

operates much like conversation between “polite people” !!!

Can transmit up to 1 GB per second

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SERVERS ON LAN

A server is a component that can be shared by the users in LAN

1) File server: dedicated PC with high-capacity hard disk for storage

2) Print server: usually in the same PC as the file server; handles print jobs for LAN

3) Communications server: controls one or more modems in order to establish communications links external to LAN

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LAN SOFTWARE

NETWORK OPERATING SYSTEMS

Is actually several pieces of softwareCertain requests within a LAN are redirected to the appropriate serverEX: Windows NT Server

APPLICATIONS SOFTWARE FOR LANs

General purpose software EX: MS Office 2000

Workgroup applicationsEX: email; electronic conferencing

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VIRTUAL LOCAL AREA NETWORKSNodes are not physically connected by the same medium.

Few people experience the rapid changes of today's business environment more than Information Technology (IT) managers. Employees move, business

operations are restructured and new technologies emerge.

All of these changes add pressure to networks already straining under the requirements of more users, more powerful workstations and more demanding

applications.

Virtual LANs (VLANs) can help IT managers adapt to these changes more easily and effectively, while increasing overall network performance. By offering a highly flexible means of segmenting a corporate network, VLANs reduce the performance bottlenecks that occur when traditional backbone routers can't

meet the demands of fast, switched networks.

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A VLAN is a group of PCs, servers and other network resources that behave as if they were

connected to a single, network segment — even though they may not be.

For example, all marketing personnel may be spread throughout a building. Yet if they are all

assigned to a single VLAN, they can share resources and bandwidth as if they were

connected to the same segment.

The resources of other departments can be invisible to the marketing VLAN members,

accessible to all, or accessible only to specified individuals, at the IT manager's discretion.

VLANs allow highly flexible, efficient network segmentation, enabling users and resources to be grouped logically, without regard to physical location.

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A typical VPN might have a main LAN at the corporate headquarters of a company, other LANs at remote offices or facilities and individual users connecting from out in

the field.

Basically, a VPN is a private network that uses a public network (usually the Internet) to connect remote sites or users together.

Instead of using a dedicated, real-world connection such as leased line, a VPN uses "virtual" connections routed through the Internet from the company's private network to the remote site or

employee.