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ILS 501
Unit 10
LAN
Dr. Yan Quan Liu
ILS SCSU
What is LAN (local area network)?
A group of computers dispersed over a local
area and connected by a communications
link that enables any device to interact with
any other on the network.
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Types:
 Client-server LAN
 Peer-to-peer LAN
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Types of LANs
Client/server LAN  Clients microcomputers
that request
data

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Server - a
powerful
microcomputer
that supplies
data and
manages
shared devices
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Types of LANs
Peer-to-peer LAN - all microcomputers on the
network communicate directly with one another
without relying on a server
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Components of LANs
Connection or cabling
system
Microcomputers with
network interface cards
Network OS
Other shared devices
Routers, bridges, and
gateways
Hub
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Wireless local area networks
(WLANs)
 A wireless LAN (or WLAN, for wireless
local area network, sometimes
referred to as LAWN, for local area
wireless network) is one in which a
mobile user can connect to a local
area network (LAN) through a
wireless (radio) connection
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802.11 tech for WLANs
 802.11 is an evolving family of
specifications for wireless local area
networks (WLANs) developed by a
working group of the Institute of
Electrical and Electronics Engineers
(IEEE). There are several
specifications in the family and new
ones are occasionally added.
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802.11 tech for WLANs
 802.11g 30 MB/s
 802.11n 300 MB/s
 802 Standard comprises a family of
networking standards that cover the
physical layer specifications of
technologies from Ethernet to
wireless
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Access Point
 "In a wireless local area network (
WLAN ), an access point is a station
that transmits and receives data
(sometimes referred to as a
transceiver). An access point
connects users to other users within
the network and ..."
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What are common network
interface devices?
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Local area network technology-
Network interface devices
Common interface drivers/receivers connecting
networks are:




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Bridge
Router
Gateway
Firewall
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Network interface devices—
Bridge
A bridge is a product that connects a local area
network to another local area network that
uses the same protocol (for example,
Ethernet)
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Network interface devices—
Router
A router is a device or software in a computer,
that determines the next network point to
which a packet should be forwarded toward
its destination.
The router is connected to networks with
different operating systems.
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Network interface devices—
Gateway
A gateway is a network point that acts as an
entrance to another network. It performs all
functions of bridges and routers but slower in
terms of speed than those two.
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Network interface devices—
Firewall
A firewall is a set of related programs, located at
a network gateway server, that protects the
resources of a private network from all
unauthorized users from other networks.
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Ending notes:
Essential Questions
 What does telecommunication mean?
 How is connection made to a network?
 What are the types and components of
communication channels?
 What does the future hold in relation to
telecommunications?
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Quick Note on Network Setups
Simple Network Dialup
 56k Modem plugged into phone line
(1 computer)
Phone
Outlet
Dialup
Modem
Computer
Note: Uses
regular
phone cable
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Quick Note on Network Setups
Simple Cable/Satellite Modem
 Cable/DSL/Satellite Modem plugged into
cable/DSL/satellite outlet (1 computer)
 Charter and SBC/Yahoo are broadband
Internet services
Cable/
Satellite
Outlet
Cable/DSL/
Satellite
Modem
Note: Uses special Category
5 (Cat 5 RJ45)
Cable called patchcords
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Computer
*Most network equipment
has a speed of 100Mbit/s
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Quick Note on Network Setups
Cable/DSL/Satellite with Hub
 Cable/DSL/Satellite Modem plugged into
cable/DSL/satellite outlet
 Requires 2 or more Internet Protocol (IP)
connections (like 2 separate phone numbers)
Cable/DSL
Satellite
Outlet
Cable/DSL
Satellite
Modem
Hub
Computer
Computer
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Quick Note on Network Setups
Cable/DSL/Satellite with Router/Switch
 Cable/DSL/Satellite Modem and Router/
Switch* plugged into cable/satellite outlet
 Requires only 1 Internet Protocol (IP)
connection (shares a phone number-saves $$)
Cable/DSL
Satellite
Outlet
Cable/DSL
Satellite
Modem
Router/
Switch
*Switches are smarter and faster than hubs
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Computer
Computer
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Quick Note on Network Setups
Cable/Satellite with Wireless
Router/Switch
 Cable/Satellite Modem and wireless
Router/Switch plugged into cable/satellite
outlet
 Requires wireless network cards. Wireless is
more convenient but less secure than Cables
Cable/
Satellite
Outlet
Cable/
Satellite
Modem
Wireless
Router/
Switch
Computer
Computer
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Quick Note on Network Setups
Firewalls
Firewalls are like the firewall in your car, which keep the
heat and noise of the engine outside the passenger
compartment
 Computer Firewalls are used to keep
unwanted Internet users from accessing your
network
 Once online, you are vulnerable w/o a firewall
 BlackIce is an example of firewall software
Firewall
Cable/
Satellite
Outlet
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Cable/
Satellite
Modem
Router/
Switch
&
Firewall
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Computer
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Quick Note on Networks
Firewalls
 Computer Firewalls work like Caller ID
 You set up the rules of who can “call”
you
 Unrecognized callers are either denied,
or asked for a password
NOTE: Some software, like PCAnywhere
and SQL Server require the firewall to
specially configured
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Questions?
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