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Technology in Action
Chapter 12
Behind the Scenes:
Networking and Security
Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall
1
Networking Advantages
• Networks
– Increase productivity
– Enable the sharing of hardware resources
– Facilitate knowledge sharing
– Enable the sharing of software
– Facilitate Internet connectivity
– Enable enhanced communication
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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
• Centralized
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Classifications of
Client/Server Networks
• LAN
– Local area
network
– Computers
linked 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 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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Classifications of
Client/Server Networks
• Extranets
– Only certain corporations or individuals can
access
– Useful for enabling electronic data
interchange
– Use virtual private networks (VPN) for security
added security measures
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Constructing
Client/Server Networks
•
•
•
•
Servers
Network topologies
Transmission media
Network operating
system (NOS)
software
• Network adapters
• Network navigation
devices (routers)
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Servers
• Number and types of servers depend on
network size and workload
• Dedicated servers: (described below)
– Perform one specific function
• Authentication servers
– Keep track of network logins and services
available
• File servers
– Store and manage files
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Servers
• Print servers
– Manage client-requested printing jobs
– Create print queue (prioritize print jobs)
• Application servers
– Act as a storage area for application software
• Database servers
– Provide clients with access to database
information
• E-mail servers
– Process and deliver incoming and outgoing
e-mail (anti-virus, anti-spam, anti-spyware,
firewall)
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Servers
• Communications servers
– Handle communications between networks,
including the Internet (firewall, anti-hacking)
– Often the only device on the network directly
connected to the Internet
• Web servers
– Host a Web site available through the Internet
– Markup pages, interaction with user
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Network Topologies
• The physical or logical 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 in
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
– 512-1024 bytes
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Ring Topology
• Nodes are laid out in
a ring.
• A token (data
packet) flows in one
direction from
device to device.
• Recent versions
have data transfer
rates of up to 100
Mbps.
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Star Topology
• Nodes connect to a central
communications device
(switch or hub).
• A node sends a signal to
the switch, which
retransmits it to the
destination node only.
• Hub-sends to all nodes
• A node accepts only
signals 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
– Twisted pair
– Coaxial
– Fiber-optic
• Wireless
•
-usually microwave, could be RF
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Choosing a Cable
•
•
•
•
•
•
•
Maximum run length
Bandwidth
Bend radius
Cable cost
Cable and installation costs
Susceptibility to interference
Signal transmission methods
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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)
– 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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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
– 802.11a
– 802.11g
– Super G
– 802.11n
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Network Operating
Systems (NOS)
• Provide the protocol that controls the
communication among devices on the
network
• Many modern OSs include NOS client
software
• Major network operating systems
– Windows Server 2008
– UNIX
– Novell Open Enterprise Server
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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 (such as
01:40:87:44:79:A5)
– Physical address of network adapter
– Internal network identification
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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 Navigation Devices
• Repeaters
– Amplify a signal and
retransmit it
– Extend cable runs
• Hubs
– Transmit signals; have
multiple ports
• Receive a signal from a
device
• Reconstruct the signal
• Transmit the signal to all
ports on the hub
(amplifies also)
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Network Security Threats
• Human errors and mistakes
• Malicious human activity
– Current and former employees hacking or
planting viruses
• Natural events and disasters
– Hurricanes, floods, fire
– Disaster Recovery Plan
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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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