Transcript Classifications of Client/Server Networks

Technology in Action
Chapter 8
Behind the Scenes:
Networking and Security
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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 transmission media
Network adapters
Moving data in a client/server network
Securing networks
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Networking Advantages
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Networks
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Increase productivity
Enable the sharing of
hardware resources
Enable the sharing of
software
Facilitate communication
inside and outside the
company
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Network Advantages
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Sharing networked hardware can reduce costs
Sharing networked hardware can provide access to
a wide range of services and specialized peripheral
devices
Sharing networked software can reduce costs
Sharing data on a network is easy
Networks enable people to work together regardless
of time and place (telecommuting)
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Network Challenges
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Networks may be vulnerable to unauthorized
access from many sources and locations
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More vulnerable than standalone computers
Wireless networks can be tapped from a
“snooping” computer
Networked computers are susceptible to an
increasing number of worms, Trojan horses,
and blended threats
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Organizational Structure:
Client/Server and Peer-to-Peer
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Where are the resources?
Centralized – Client/Server
 resources in the Server(s)
 Distributed – Peer-to-Peer (file sharing)
 resources in all the machines
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Organizational Structure:
Client/Server and Peer-to-Peer
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Client/Server Networks
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Server-based network
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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
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LAN
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Local area network
Computers linked
together over a small
geographic region
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Classifications of
Client/Server Networks
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WAN
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Wide area network
Computers linked
over large
geographic locations
MAN
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Metropolitan area
network
Computers linked
together within a city
or county
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Classifications of
Client/Server Networks
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PAN
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Personal area network
Wireless devices connected in close proximity to
each other
Intranet
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Private corporate network using TCP/IP
Protected by a firewall from the Internet outside
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Constructing
Client/Server Networks
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Servers
Transmission media
Network adapters
Network navigation
devices
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Servers
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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
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Communications server
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Handles communications between networks
including the Internet
Often the only device on the network directly
connected to the Internet
Web server
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Hosts a Web site available through
the Internet
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Dedicated Servers, cont'd
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Print server
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Applications server
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Acts as a storage area for application software
Database server
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Manages client-requested printing jobs
Creates print queue (prioritizes print jobs)
Provides clients with access to database information
E-mail server
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Processes and delivers incoming and outgoing
e-mail
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Transmission Media
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The routes data takes to flow between
devices on a network
Wired
Wireless
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Network Links
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Wired network
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Twisted-pair cable
Coaxial cable
Fiber-optic cable
Wireless network
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RF signals
Microwaves
Infrared light
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Choosing a Cable
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Maximum run length
Bandwidth
Bend radius
Cable cost
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Installation costs
Susceptibility to interference
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
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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
UTP
STP
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Coaxial Cable
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Four components
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Copper core
Nonconductive insulating material
Braided metal
Plastic cover
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Fiber-Optic Cable
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Components include
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Glass or plastic fibers
Cladding
Outer jacket
Uses light impulses
to transmit data
Immune to interference
Physically smaller
More difficult to install
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Network Adapters
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Devices that enable computers to
communicate on a network
Network interface cards (NICs)
Three functions
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Generate network transmission signals
Create data packets
Act as information gatekeepers
Ethernet compliant
Wireless NICs
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Wired Ethernet Networks
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Protocol created by Xerox PARC in 70’s
Bandwidth from 10/100 Mbps to 1 Gbps
Connection with Unshielded Twisted Pair
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Cat 5, Cat 5E, Cat 6
Network interface card added if not builtin
Switch device works to send data where it
goes, avoiding collisions
Routers work between two networks, like
your network and the Internet
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Wireless Ethernet Networks
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Use radio instead of wires
Wi-Fi = 802.11 standard
Need a wireless network adapter for each
machine – transmits and receives signals
Radio signals can be blocked by walls,
reduced by distance
WAP – wireless access point – will extend
the range
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Wireless Media
802.11 Standard
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Wi-Fi, short for Wireless Fidelity
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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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Grid computing
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Loosely connected networks of machines
volunteered to work on research
Donate your unused cycles to research
CPUs are idle a lot, software has been
written to make use of those idle machine
cycles
Download software that connects you
SETI, medicine, mathematics, astrophysics
Make sure it’s a project that is legitimate
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“Cloud computing”
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The Internet is “the cloud”
Your data is stored on servers remotely, not
on your local hard drive
Applications you run (even Office) are via a
web browser
Portable
Cheaper? “software as service”
Like plugging into the wall vs. owning a
generator
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Network Security Threats
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Human Errors and Mistakes
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Malicious Human Activity
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Accidents and mistakes
Current and former employees hacking or planting
viruses
Natural Events and Disasters
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Hurricanes, floods, fire
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Computer Threats
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Hackers and Crackers
Viruses
Trojan Horses
Worms
Bots
Combating Malicious Code "Malware"
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Hackers and Crackers
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Why do they do it?
 To
show off their technical expertise
 blackmail
 espionage
 industrial
 military
 Theft
 Global terrorism
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Viruses
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Viruses are malicious code that enters a
computer and disrupts normal operation
Viruses might deliver a payload, which could
either be annoying or devastating
Trigger events can unleash some viruses
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When you check email
On a certain date/time
When your computer starts up
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Viruses
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Computer viruses attach themselves to a file,
reproduce, and spread to other files and computers
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File virus
Boot sector virus
Macro / script virus
Email virus
Main goal is to reproduce itself
Attempts to be unnoticed - stealth mode
Depends on the user to execute a program or open a
file to get started
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Trojan Horses
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Seems to perform one function while doing
another
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Keyloggers record your keystrokes
Backdoors allow unauthorized access to
computers
Wants to be noticed - looks desirable to get
itself installed
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A funny video or a cool game
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Worms
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Designed to spread from computer to
computer - more active than a virus or Trojan
Will send ITSELF without user knowledge if
there is a network connection available
Mass-mailing worms spread to addresses in
the address book on the infected computer
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Examples include Klez, Netsky, Sasser
Messages sometimes contain a spoofed address
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Bots
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A bot is software that can automate a task or
autonomously execute a task
Bots can be useful – system administrators
use them to do repetitive work more quickly
than a human could, “spiders” are bots
Bots can be the payload of a virus or Trojan
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Botnets are linked bot-infested computers
Bots can be networked to make a botnet
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Used for “DOS” attacks
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What can they do?
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Malicious code can perform the following activities:
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Network traffic jam
Denial of Service attacks
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Bot nets
Browser reconfiguration
Delete and modify files
Access confidential information
Performance degradation
Disable antivirus and firewall software
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Network Security
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Authentication
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Access privileges
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User ID and password used to access the network
Use of a possessed object for access
Enable access to certain network systems
Physical protection measures
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Restrict physical access to sensitive network equipment
Magnetic card readers
Biometric access devices
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Network Security
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Firewalls
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Prevent access to the network by
unauthorized users
Composed of software and/or hardware
Screen and validate data packets
Software firewalls
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Norton, McAfee, ZoneAlarm, BlackICE
Hardware firewalls
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Usually built into routers
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Network Firewall Layout
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Combating Malicious Code
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Use antivirus software and firewall software on
every computing device you own
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keep them up to date
Virus signatures keep changing
McAfee software freely available on
download.uky.edu to all UK students
AVG software www.avg.com free for home use
Do not open suspicious e-mail attachments
Regularly download and install the latest
security patches available for your OS, e-mail
program, and browser.
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Combating Malicious Code
Limit sharing disks and other removable
storage media.
 Only download programs from reputable Web
sites.
 Limit the amount of file-sharing you do
 Use anti-virus software to scan all emails and
all files received from someone else
 Backup your files regularly
 Look for unexpected file extensions – like exe
on a jpg file
 Test your computer with Gibson Research’s
free scan
© 2008 Prentice-Hall, Inc.
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Protecting a Wireless Network
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Change your network’s name
Disable the broadcast of its name (SSID)
Change the default password on your router
Turn on WEP (wired equivalent privacy)
(weak) or WPA (wi-fi protected access)
Turn on MAC addresses – so only computers
whose addresses you enter are allowed on
Keep software up to date
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