Transcript Lecture 2 Digital Data Representation (1)

Week 12 (2012)
Dr. Ghada Drahem
INTENDED LEARNING OUTCOMES
 This lecture covers:
 Networking concepts and terminology
 Common networking and communications applications
 Technical issues related to networks, including the major types of
networks, how data is transmitted over a network, and types of
transmission media involved
 Explanation of the various ways networked devices communicate with one
another
 Various types of hardware used in conjunction with a computer network
WHAT IS A NETWORK?
 Network: A connected system of objects or people
 Computer network: A collection of computers and
other hardware devices connected together so that
users can share hardware, software, and data, as well
as electronically communicate with each other
 Internet: Largest computer network in the world
 Types of networks
 Business networks
 Phone networks
 Home and multimedia networks
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NETWORKING AND
COMMUNICATIONS APPLICATIONS
 Mobile phones (wireless phones)
 Cellular (cell) phones

Must be within range of cell tower to function
 Satellite phones

Used where cell service isn’t available
 Dual-mode phones


Allows users to make telephone calls on more than one
network
Cellular / Wi-Fi dual mode phone are most popular
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NETWORKING AND
COMMUNICATIONS APPLICATIONS
 Paging
 Sending short numeric or
text messages to a
person’s pager
 Most often used for onsite
paging applications
 Messaging
 Two-way paging
 Most often takes place
today via a mobile phone
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NETWORKING AND
COMMUNICATIONS APPLICATIONS
 Global positioning system (GPS): Uses satellites and
a receiver to determine the exact geographic
location of the receiver
 Commonly found in cars today
 Available as handheld units
 Used by the military, hikers, travelers,
and others who need to know their
precise location
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NETWORKING AND
COMMUNICATIONS APPLICATIONS
 Videoconferencing: Use of communications
technology for real-time, face-to-face meetings
between individuals located in different places
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TYPES OF NETWORKS
 Topology: How the devices in the network (called
nodes) are arranged
 Star networks: All devices connect to a central device or




hub)
Bus networks: All devices connect to a central cable
Ring networks: Devices connect to one another in a ring
Mesh networks: Multiple connections between devices
Some networks use a combination of topologies
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NETWORK TOPOLOGIES
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TYPES OF NETWORKS
 Client-server networks
 Client: PC or other
device on the network
that requests and
utilizes network
resources
 Server: Computer
dedicated to
processing client
requests
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TYPES OF NETWORKS
 Peer-to-peer networks: All computers at the same
level
 Internet peer-to-peer (P2P) computing: Performed
via the Internet
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TYPES OF NETWORKS
 Local area network (LAN): Small geographical area
(office, campus, etc.)
 Wide area network (WAN): Large geographical area
(Internet)
 Metropolitan area network (MAN): Serves a
metropolitan area
 Personal area network
(PAN): Connects personal
devices for one individual,
such as his or her portable
PC, mobile phone, and
portable printer
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TYPES OF NETWORKS
 Wireless sensor networks (WSNs): Contain sensors
(devices that respond to a stimulus and generate an
electrical signal that can be measured or interpreted)
 Intranet: Private network set up by an organization
for use by its employees
 Extranet: Intranet that is at least partially accessible
to authorized outsiders
 Virtual private network (VPN): Secure path over the
Internet that provide authorized users a secure means
of accessing a private network via the Internet
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DATA TRANSMISSION CHARACTERISTICS
 Analog vs. digital (waves vs. discrete)
 Bandwidth: The amount of data
that can be sent at during a given
period of time
 Measured in bits per second (bps)
 Serial vs. parallel
transmission
 Serial = 1 bit
 Parallel = at
least 1 byte at
a time
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DATA TRANSMISSION CHARACTERISTICS
 Transmission timing
 Synchronous transmission (at regular, specified
intervals)
 Asynchronous transmission (sent when ready)
 Isochronous transmission (sent at the same time as
other, related, data)
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DATA TRANSMISSION CHARACTERISTICS
 Transmission directions
 Simplex transmission (one way only)
 Half-duplex transmission (one way at a time)
 Full-duplex transmission (both ways at the same time)
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DATA TRANSMISSION CHARACTERISTICS
 Type of connections
 Circuit-switched: Dedicated path over a network is
established and all data follows that path
 Packet-switched: Messages are separated into small
units called packets and travel along the network
separately

Used to send data over the Internet
 Broadcast: Data is sent out to all other nodes on the
network

Primarily used with LANs
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TYPE OF CONNECTIONS
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DATA TRANSMISSION CHARACTERISTICS
 Wired connections: The PC is physically cabled to
the network
 Common in schools, business, and government
facilities
 Wireless connections: Typically use radio waves to
send data through the air
 Rapidly becoming more popular in homes and
businesses
 Wireless hotspots are commonly available in public
locations
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WIRED NETWORK TRANSMISSION MEDIA
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WIRELESS NETWORK TRANSMISSION MEDIA
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CELLULAR RADIO TRANSMISSIONS
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MICROWAVE AND SATELLITE
TRANSMISSIONS
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NETWORKING STANDARDS AND
COMMUNICATIONS PROTOCOLS
 Standards: A set of criteria or requirements considered to be
the approved model for something
 Networking standards: Address how networked computers
communicate and connect
 Communications protocol: An agreed-upon standard for
transmitting data between two devices on a network
 In networking, standards and protocols specify how:
 Devices physically connect to a network
 Data is packaged for transmission
 Receiving devices acknowledge signals
 Errors are handled
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ETHERNET
communications protocol
 Ethernet: Most widely used communications protocol for
wired LANs
 Typically used a bus or star topology and twisted-pair,
coaxial, or fiber-optic cables
 Power over Ethernet: Allows electrical power to be sent
along with data on an Ethernet network
 Most often used by businesses
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TCP/IP AND WIRELESS APPLICATION PROTOCOL
(WAP)
 TCP/IP (Transmission Control Protocol/Internet Protocol):
Used for transferring data over the Internet
 Wireless Application Protocol (WAP):
A standard for delivering Internet
content to mobile devices
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