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Technology in Action
© 2008 Prentice-Hall, Inc.
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Technology in Action
Chapter 12
Behind the Scenes:
Networking and Security
© 2008 Prentice-Hall, Inc.
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Chapter Topics
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Advantages of business networks
Client/server vs. peer-to-peer networks
Classifications of client/server networks
Client/server network components
Types of servers
Network topologies
Types of transmission media
Network software
Network adapters
Moving data in a client/server network
Securing networks
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Networking Advantages
• Networks
– Increase productivity
– Enable the sharing of
hardware resources
– Enable the sharing of
software
– Facilitate Internet
connectivity
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Client/Server Networks
• Server-based network
– Clients and servers
• Data flows efficiently
• Servers respond to
requests from clients
• Servers perform
specific tasks
• Scalable network
• Centralized
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Classifications of
Client/Server Networks
• LAN
– Local area network
– Computers linked
together over a
small geographic
region
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Classifications of
Client/Server Networks
• WAN
– Wide area network
– Computers linked
over large
geographic
locations
• MAN
– Metropolitan area
network
– Computers linked
together within a
city or county
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Classifications of
Client/Server Networks
• PAN
– Personal area network
– Wireless devices connected in close proximity
to each other
• Intranet
– Private corporate network
– Protected by a firewall
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Constructing
Client/Server Networks
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Servers
Network topologies
Transmission media
Network operating
system (NOS)
• Network adapters
• Network navigation
devices
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Servers
• Number and type of
servers depend on
network size and
workload
• Dedicated server
– Performs one specific
function
• Authentication server
– Keeps track of network
logins and services
available
• File server
– Stores and manages files
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Dedicated Servers
• Print server
– Manages client-requested printing jobs
– Creates print queue (prioritizes print jobs)
• Applications server
– Acts as a storage area for application software
• Database server
– Provides clients with access to database
information
• E-mail server
– Processes and delivers incoming and outgoing
e-mail
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Dedicated Servers
• Communications server
– Handles communications between networks
including the Internet
– Often the only device on the network directly
connected to the Internet
• Web server
– Hosts a Web site available through
the Internet
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Network Topologies
• The physical layout of computers,
transmission media, and other
components
• Types of network topologies
– Bus topology
– Ring topology
– Star topology
– Hybrid topology
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Bus Topology
• All nodes are connected in
sequence on a single cable
• Used most often on
peer-to-peer networks
• Networked computers
communicate with each
other
• One computer transmits
data at a time
– Access methods avoid data
collisions
– Data is transmitted in
“packets”
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Ring Topology
• Nodes are laid out in
a ring
• Token (data packet)
flows in one
direction from
device to device
• Recent versions
have data transfer
rates up to 100
Mbps
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Star Topology
• Nodes connect to a central
communications device
(switch)
• A node sends a signal to
the switch, which
retransmits it to the
other nodes
• A node accepts only
signal addressed to it
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Avoiding Data Collisions
on an Ethernet Network
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Transmission Media
• The routes data takes to flow between
devices on a network
• Wired
• Wireless
– Wireless Fidelity (Wi-Fi)
– Uses radio waves
– 802.11 standard
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Choosing a Cable
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• Installation costs
• Susceptibility to interference
• Signal transmission methods
Maximum run length
Bandwidth
Bend radius
Cable cost
Comparison of Characteristics of Major Cable Types
Cable Characteristics
Twisted Pair (Cat 6)
Coaxial (ThinNet)
Coaxial (ThickNet)
Fiber-Optic
Maximum
Run Length
328 feet (100 m)
607 feet (185 m)
1,640 feet (500m)
Up to 62 miles (100 km)
Bandwidth
1,000 Mbps
10 Mbps
10 Mbps
100 Mbps to 2 Gbps
Bend Radius
(Flexibility)
No limit
360 degrees/foot
30 degrees/foot
30 degrees/foot
Cable Cost
Very low
Low
Moderate
High
Installation Cost
Very low
Low
Slightly higher
than ThinNet
Most expensive because of
Installation training required
Susceptibility
to Interference
High
Low
Very low
None (not susceptible
to EMI and RFI)
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Twisted Pair Cable
• Pairs of copper wire twisted
around each other
• Twists make the wires less
susceptible to interference
• Shielded twisted pair (STP)
UTP
– Layer of foil shielding
• Unshielded twisted pair (UTP)
– Cat 5E: Bandwidth 200 Mbps
– Cat 6: Bandwidth 1 Gbps
– No foil layer
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STP
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Coaxial Cable
• Four components
– Copper core
– Nonconductive insulating material
– Braided metal
– Plastic cover
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Fiber-Optic Cable
• Components include
– Glass or plastic fibers
– Cladding
– Outer jacket
• Uses light impulses
to transmit data
• Immune to
interference
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Wireless Media
802.11 Standard
• Wi-Fi, short for Wireless Fidelity
– 802.11b – first cost-effective wireless devices.
– 802.11a, 802.11g – bandwidth increased to 54
Mbps
– Super G – bandwidth to 108 Mbps
– 802.11n – will support higher throughput and
greatly increased range
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Network Operating Systems (NOS)
• Provide the protocol that
controls the communication
between devices on the
network
• Major network operating
systems
– Windows Server 2003
– UNIX
– Novell NetWare
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Network Adapters
• Devices that enable computers to
communicate on a network
• Network interface cards (NICs)
• Three functions
– Generate network transmission
signals
– Create data packets
– Act as information gatekeepers
• Ethernet compliant
• Wireless NICs
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Network Navigation Devices
• Media Access Control
(MAC) address
– Six two-digit numbers
(01:40:87:44:79:A5)
– Physical address of
network adapter
– Internal network
identification
• Repeaters and Hubs
– Amplify signals and
retransmit them
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Network Navigation Devices
• Switches and
Bridges
– Send data on a
specific route
through the network
– Bridges send data
between collision
domains
• Routers
– Send information
between two
networks
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Network Security Threats
• Human Errors and Mistakes
– Accidents and mistakes
• Malicious Human Activity
– Current and former employees hacking or
planting viruses
• Natural Events and Disasters
– Hurricanes, floods, fire
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Network Security
• Authentication
– User ID and password used to access the network
– Use of a possessed object for access
• Access privileges
– Enable access to certain network systems
• Physical protection measures
– Restrict physical access to sensitive network
equipment
– Magnetic card readers
– Biometric access devices
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Network Security
• Firewalls
– Prevent access to the network by
unauthorized users
– Composed of software and/or hardware
– Screen and validate data packets
– Bastion host/proxy server
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Network Firewall Layout
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Chapter 12 Summary Questions
• What are the advantages of a business
network?
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Chapter 12 Summary Questions
• How does a client/server network differ
from a peer-to-peer network?
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Chapter 12 Summary Questions
• What are the different classifications of
client/server networks?
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Chapter 12 Summary Questions
• What components are needed to construct
a client/server network?
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Chapter 12 Summary Questions
• What do the various types of servers do?
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Chapter 12 Summary Questions
• What are the various network topologies?
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Chapter 12 Summary Questions
• What types of transmission media are
used in client/server networks?
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Chapter 12 Summary Questions
• What software needs to be running on
computers attached to a client/server
network?
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Chapter 12 Summary Questions
• How do network adapters enable
computers to participate in a client/server
network?
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Chapter 12 Summary Questions
• What devices assist in moving data
around a client/server network?
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Chapter 12 Summary Questions
• What measures are employed to keep
large networks secure?
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