Transcript Network

Technology
Briefing
TB-1
Advanced Topics and Trends in
Managing the Information
Systems Infrastructure
(telecommunication Network)
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4/11/2016
Computer Networks
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 Network- A group of computer and associated peripheral devices
connected by a communication channels capable of sharing data &
other resources
 Components: minimum 2 computers, telecommunication devices,
communication channels, data & protocols
 Evolution of network: Centralized, distributed & collaborative
IS Today (Valacich & Schneider)
Copyright © 2010 Pearson Education, Inc. Published as Prentice Hall
4/11/2016
Centralized Computing
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 Period of 1940s – 1970s
(mainframe era)
 Central computer
(mainframe)
 Processing and
storage of data
 Terminal
 Local input/output
device
 Not a true network –
no information sharing
IS Today (Valacich & Schneider)
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4/11/2016
Distributed Computing
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 Period of 1980s
 Driver: Introduction of
PCs
 Organization can used
multiple small computers
to achieve many of same
processing powers of a
single mainframe
 Separate computers work
on subsets of tasks
 Results are pooled via
network
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4/11/2016
Collaborative Computing
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 Period of 1990s
 Synergistic form of distributed computing in which two or
more networked computers are used to accomplish a
common processing task.
 Driver: PC become more powerful as mainframe of 70s
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4/11/2016
Computing Networks Today
1-6
 All types are still present (centralized, distributed,
collaborative)
 Usually combined into a network (Networks classified by
size, distance covered and structure):
 Local Area Network (LAN)Private branch Exchange (PBX); Personal Area
Network (PAN)
 Wide area network (WAN)Global Network; Enterprise Network; Value-Added
Network (VAN); Metropolitan Area Network (MAN)
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4/11/2016
Local Area Network
1-7
 Covers a relatively small area, such as a building or floor
 Computers share: Information and Peripheral devices
 Usually one type of cable used
 May includes a Wireless Local Area Network (WLAN)
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4/11/2016
Private Branch Exchange (PBX)
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 Telephone system
serving a particular
location
 Connects phones and
computers
 Connects PBX to
outside network
 Limited bandwidth
because of limited
phone line capacity
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4/11/2016
Personal Area Networks
1-9
 Exchange data between
computing devices
 Short range radio
communication –
10 meters
 E.g., networking of
PCs, peripheral
devices, mobile
phones, portable
stereos, etc.
 Enabling Technology:
Bluetooth
IS Today (Valacich & Schneider)
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4/11/2016
Wide Area Network
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 Spans relatively large area.
 Usually connects multiple LANs and have Different hardware and
transmission media used
 Used by multinational companies
 Information transmitted across cities and countries
 4 specific types of WAN:
a) Global networks: Span multiple countries. E.g., The Internet
b) Enterprise networks: Connect disparate networks of a single
organization
c) Value-added networks (VAN): is Medium speed WANs, Third
party managed and Shared by multiple organizations
d) Metropolitan area networks (MAN): Limited geographic scope –
usually a citywide area
IS Today (Valacich & Schneider)
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4/11/2016
Networking Fundamentals
1-11
 Three different roles: Servers, Clients &
Peers
 Server: Only provide services. Usually
have: More advanced micro-processors;
More memory. It allows many users to
share services
 Clients: computer that request services.
Can be workstations, PCs, or Software
applications. Usually one user per client.
 Peer: May request and provide services.
Usually use Peer-to-peer networks.
Has Equivalent capabilities and
responsibilities. Usually found in small
offices and homes
IS Today (Valacich & Schneider)
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4/11/2016
Network Services
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 (a) File services: Store,
retrieve and move data files
 (b) Print services: Control
and manage access to
printers
 (c) Message services: Store,
access and deliver data
 (d) Application Services:
Run software for network
clients, Enable computers
to share processing power
IS Today (Valacich & Schneider)
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4/11/2016
Network Operating System (NOS)
1-13
 System software controlling the network
 Enables computers to communicate with each others
 Two parts:
Network server
 Coordinates: user accounts, information access,
security, resource sharing
 Workstation
 Runs on top of the local OS
 Sometimes integrated into the OS
 Example: Novell NetWare, Microsoft Windows Server

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Transmission Media/Communication
Channel
1-14
 Physical pathways for sending data.
 Two types: Cable media (twisted-pair, coaxial, fiber-optic); Wireless
media (infrared LOS, HF radio signal, microwave
 Effectiveness is influenced by:
Bandwidth: Transmission capacity of a computer or a communications
channel. Measured in megabits per second (Mbps). Bigger
bandwidth = faster transmission
Attenuation: Power of an electric signal weakens with distance. How far
can a signal travel with the same properties and meaning? Shorter
distance = lesser attenuation = faster transmission
Electromagnetic interference (EMI): Interference by fluorescent light,
weather or other electronic signals. Lesser EMI = faster
transmission
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Cable Media: Twisted Pair Cable
1-15
 Two or more insulated pairs of cable.
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Unshielded (UTP): Telephone wire, Cheap and easy to install. Up to 1
Gbps at distance up to 100 meters. Rapid attenuation – sensitive to
EMI and eavesdropping
Shielded (STP): Less prone to EMI and eavesdropping. More
expensive and harder to install. 500 Mbps up to 100 meters
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4/11/2016
Coaxial Cable
TB-16
 Components
Solid inner
copper conductor
 Plastic insulation
 Outer braided
copper or foil
shield
 Used for cable
television and
networks operating
at 10-100 Mbps

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Fiber-Optic Cable
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 Components:
 Light-conducting glass or
plastic
 Cladding (glass)
 Tough outer sheath
 Transmission:
 Pulses of light
 Immune to EMI and
eavesdropping
 Low attenuation
 100 Mbps to more than 2
Gbps
 2 to 25 kilometers
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4/11/2016
Key Benefits & Drawback of media
1-18
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Wireless Media: Infrared Line of Sight
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High frequency light waves
Distance of up to 24.4 meters
Attenuation, EMI and eavesdropping problems
Relatively inexpensive
Two types:
 Point-to-point
 Strict line of sight
 Up to 16 Mbps at 1 meter
 Example: TV remote
 Broadcast
 Devices don’t need to be directly in front of each
other
 Less than 1 Mbps
IS Today (Valacich & Schneider)
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4/11/2016
Wireless Media: High Frequency Radio
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 Ideal for mobile transmission
 Expensive due to cost of
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antenna towers
Complex installation
Susceptible to EMI and
eavesdropping
Attenuation not a problem
Distance between nodes 12.2–
40 kilometers
Rate up to several hundred
Mbps
Examples: cellular phones and
wireless networks
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4/11/2016
Wireless Media: Microwave
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 High-frequency radio
 Terrestrial microwave: Line-of-
sight; Transmission up to 274 Mbps;
EMI and eavesdropping problems;
Cross inaccessible terrain;
Alternative when cabling too ;
expensive
 Satellites microwave:
Propagation delay; Satellites orbit
400-22,300 miles
above earth; Typically 1-10 Mbps, up
to 90 Mbps; Prone to attenuation;
Susceptible to EMI and
eavesdropping
IS Today (Valacich & Schneider)
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4/11/2016
Relative Comparison of Wireless Media
TB-22
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4/11/2016
Network Topologies
TB-23
 Topologies: The physical
layout of nodes and
transmission media. Types
include:
 Star: All workstations
connected to a central hub.
Easy to lay out and modify.
Most costly (cabling). Failure of
hub can cause network failure.
 Ring: Messages move in one
direction around the circle.
Covers large distances.
Relatively little cabling. Failure
of one node can cause network
failure
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Copyright © 2010 Pearson Education, Inc. Published as Prentice Hall
4/11/2016
Network Topologies (ii)
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 Bus: Open-ended line. Easiest
to extend. All nodes can receive
the same message at the same
time. Difficult to diagnose
network faults
 Mesh: Devices fully or partially
connected to each other. Short
routes between nodes. Many
possible routes. Performs well
in heavy traffic
IS Today (Valacich & Schneider)
Copyright © 2010 Pearson Education, Inc. Published as Prentice Hall
4/11/2016
Protocols
TB-25
 Rules or procedures used to transmit and receive data
 Specify: Connection of computers to the network, Error checking, Data
compression, Signal of finished transmission, and Signal of received
message
 There are thousands of protocols: OSI, Ethernet, TCP/IP
 Ex: Open system interconnection (OSI
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Connectivity Hardware
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 Devices that facilitate
transmission between two nodes.
Include:
 Connectors: Used to terminate a
cable. Ex: RJ-45 connectors
(twisted pair cable)
 Network interface cards: PC
expansion board. Allows
computer to be connected to a
network. Each NIC has a unique
identifier
 Modem: Enable transmission
over telephone lines. Digital
signal converted to analog
IS Today (Valacich & Schneider)
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4/11/2016
Other Networking Hardware
TB-27
Repeaters – replicate signal
Hubs – central point of connection
Bridges – connect two different LANs
Multiplexers – used when communication line is shared
Routers – connect 2 or more individual networks
Brouters – capabilities of bridge and router
Channel service unit – buffer between LAN and public
carrier’s WAN
 Gateway – performs protocol conversion
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IS Today (Valacich & Schneider)
Copyright © 2010 Pearson Education, Inc. Published as Prentice Hall
4/11/2016