Networks
• A network is a collection of computers and
devices connected together via communications
devices and transmission media
• Advantages of a network include:
Facilitating
communications
Sharing
software
Sharing
hardware
Sharing data
and information
Transferring
funds
1
2
Bandwidth
• Measurement of the capacity of the channel
• Categories
– Voiceband also known as low bandwidth
– Medium band
– Broadband
• Used for high capacity transmission
• Used by DSL, cable, and satellite
Protocols
• Set of communication rules
• Standard for Internet: TCP/IP (Transmission
control protocol/Internet protocol)
– Identification
– Reformatting
Network Classifications
• Local area networks (LAN)
• Home networks
– WLAN (Wireless LAN)
• Metropolitan area networks (MAN)
• Wide area networks (WAN)
5
Network Classifications
• A local area network
(LAN) is a network that
connects computers
and devices in a limited
geographical area
• A wireless LAN (WLAN)
is a LAN that uses no
physical wires
6
Network Classifications
• A metropolitan area network (MAN) connects
LANs in a metropolitan area
• A wide area network (WAN)
is a network that covers a
large geographical area
7
Network Architecture
• The design of computers, devices, and media on a
network is sometimes called the network architecture
Client/server
Peer-to-peer
Terminal
8
Client/Server Model
Client
Peer-to-peer
(P2P) Model
Client
Peer
Peer
Server
Client
Client
Peers communicate as equals
on a one-to-one basis.
Server must be prepared to serve multiple
clients at any time.
9
The Client/Server Model
• When processes need to communicate:
• Examples:
– file server
– mail server
– web server
=>
10
The Client/Server Model (continued)
• Client & server have strictly defined roles:
– client sends request – then waits for answer
– server accepts request – processes & returns answer
• Protocols, defining how to:
– encode messages
– address messages
– handle sending and
receiving
• Protocols: Example
• http, ftp
11
The Peer-to-peer Model
• P2P describes an Internet network on which users
access each other’s hard disks and exchange files
directly over the Internet
12
Network Topology
• A network topology refers to the layout of the computers
and devices in a communications network
Star network
Bus network
Ring network
13
Network Topology
• Network topology is the layout pattern of
interconnections of the various elements
(links, nodes, etc.) of a computer.
• Types of network topology
– Star
– Bus
– Ring
– Hierarchical
Star Network
• Smaller computers
linked to a central unit
• Central unit is called the
network hub
• Control is maintained by
polling
15
Bus Network
• Each device handles its own communication control
• There is no host computer
• Has a common connecting cable called a backbone
16
Ring Network
• Each device is
connected to two other
devices
• No central file server or
computer
• Useful in a
decentralized
environment
17
Hierarchical Network
• Several computers
linked to a central host
• Computers are hosts to
other computers
• Useful in centralized
organizations
Page 264
18
Principal Network Configurations
Network Communications Standards
Ethernet
Token
ring
TCP/IP
Wi-Fi
Bluetooth
UWB
IrDA
RFID
WiMAX
WAP
20
Network Communications Standards
Ethernet is a network standard that specifies no computer
controls when data can be transmitted
The token ring standard specifies that computers and
devices on the network share or pass a special signal (token)
TCP/IP is a network standard that defines how messages are
routed from one end of a network to another
21
Network Communications Standards
22
Network Communications Standards
• Wi-Fi identifies any
network based on the
802.11 standard that
facilitates wireless
communication
• Sometimes referred to
as wireless Ethernet
23
Network Communications Standards
• Bluetooth defines how two Bluetooth devices use shortrange radio waves to transmit data
• UWB (ultra-wideband) specifies how two UWB devices use
short-range radio waves to communicate at high speeds
• IrDA transmits data wirelessly via infrared (IR) light waves
• RFID uses radio signals to communicate with a tag placed in
or attached to an object, animal, or person
24
Network Communications Standards
25
Network Communications Standards
WiMAX (802.16)
Wireless Application
Protocol (WAP)
• Developed by IEEE
• Towers can cover a 30-mile
radius
• Two types are fixed
wireless and mobile
wireless
• Provides wireless
broadband Internet access
• Specifies how some mobile
devices can display the
content of Internet services
• Web
• E-mail
• Chat rooms
• Uses a client/server
network
26
Communications Software
• Communications software consists of programs
that:
Help users establish
a connection to
another computer
or network
Manage the
transmission of
data, instructions,
and information
Provide an
interface for users
to communicate
with one another
27
Communications Over
the Telephone Network
• The public switched telephone network (PSTN) is
the worldwide telephone system
28
Communications Over
the Telephone Network
Dial-up
lines
DSL
Dedicated
line
ISDN line
FTTP
T-carrier
line
ATM
29
Communications Over
the Telephone Network
30
Communications Over
the Telephone Network
• ADSL connections transmit data downstream at a
much faster rate than upstream
31
Home Networks
• Home networks provide computers with the
following capabilities:
Connect to the
Internet at the
same time
Share a single highspeed Internet
connection
Play multiplayer
games
Access files and
programs on other
computers
Connect game
consoles to the
Internet
Share peripherals
Subscribe to and
use VoIP
32
Home Networks
33
Organizational Internets
• Intranets
– Private network within an organization
– Provides information to employees
• Extranets
– Private network that connects
organizations
– Used to allow suppliers and others
access
• Firewalls
– Security system
– Protects against external threats
34
Careers In IT
• Network Administrator
– Manage a company’s LAN and
WAN networks
– Maintain hardware and
software
– Diagnose and repair problems
– Candidates usually have a
bachelor’s degree in
computer science and
practical experience
– Annual salary is typically
between $43,000 and
$68,000
35