Transcript Local area Network

WHY NEED NETWORKING?
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Access to remote information
Person-to-person communication
Cooperative work online
Resource sharing
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NETWORKING
1) 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 PROTOCOL
Communications 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
5 Layers of TCP/IP
Data Link
Physical
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TYPES OF NETWORKS
1. Wide Area Network (WAN)
2. Metropolitan Area Network (MAN)
3. Local area Network (LAN):
connects nodes in close proximity
LOCAL AREA NETWORKS
Valuable resources can be shared by all
computers networked in LAN:
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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)
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LAN ACCESS METHODS
1) TOKEN ACCESS METHOD:
an electronic “token” travels around a ring of nodes
header 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 software
The 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 software
Certain requests within a LAN are redirected to the appropriate server
EX: Windows NT Server
APPLICATIONS SOFTWARE FOR LANs
General purpose software
EX: MS Office 2000
Workgroup applications
EX: email; electronic conferencing
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VIRTUAL LOCAL AREA NETWORKS
Nodes 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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VLANs allow highly flexible, efficient network segmentation, enabling users and resources to
be grouped logically, without regard to physical location.
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.
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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.
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