C20 Extra Networks tia7e ch12 ppt - wmich.edu · 2011-08-17 · 8/17/11 2 Classifications of...

8/17/11

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Computer Networks

Behind the Scenes: Networking and Security

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 1

Network Topics •  Advantages of business networks •  Classifications of client/server networks •  Client/server network components •  Types dedicated of servers •  Network topologies •  Types of transmission media •  Network operating software •  Network adapters •  Client/server network navigation devises •  Securing networks

Networking Advantages

•  Business Networks –  Increase productivity – Enable the sharing of hardware resources – Facilitate knowledge sharing – Enable the sharing of software – Facilitate Internet connectivity – Enable enhanced communication – Select client/server vs. peer-to-peer networks


Client/Server Networks

•  Data flows efficiently •  Servers respond to

requests from clients •  Servers perform

specific tasks •  Scalable •  Centralized


Classifications of Client/Server Networks

•  HAN –  Home area network –  Connects digital devices within a home


•  LAN –  Local area

network –  Computers linked

over a small geographic area


•  WAN –  Wide area

network –  Computers

linked over large geographic areas

•  MAN –  Metropolitan

area network –  Computers

linked within a city or county


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•  PAN – Personal area network – Wireless devices connected in close proximity

to each other •  Intranet

– Private corporate network – Protected from the Internet by a firewall



•  Extranets – Only certain corporations or individuals can

access – Useful for enabling electronic data

interchange – Use virtual private networks for security


Constructing Client/Server Networks

•  Servers •  Network

topologies •  Transmission

media •  Network operating

system software •  Network adapters •  Network

navigation devices


Dedicated Servers •  The number and types of servers depend

on network size and workload •  Dedicated servers

– Perform one specific function •  Authentication servers

– Keep track of network logins and services available

•  File servers – Store and manage files


Dedicated Servers •  Print servers

– Manage client-requested printing jobs – Create a 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


Dedicated Servers

•  Communications servers – Handle communications between networks,

including the Internet – Often the only device on the network directly

connected to the Internet •  Web servers

– Host a Web site available through the Internet


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Network Topologies

•  The physical or logical layout of computers, transmission media, and other components

•  Types of network topologies – Bus – Ring – Star – Hybrid


Bus Topology •  All nodes are connected in sequence on a single

cable •  Networked computers communicate with each

other •  One computer transmits data at a time •  Becoming obsolete


Avoiding Data Collisions on an Ethernet Network


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


Star Topology •  Most widely deployed

client/server layout •  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 signals addressed to it


Comparing Technologies


Topology Advantages Disadvantages Bus Uses a minimal amount of cabling. Breaks in the cable can disable the network.

Easy, reliable, and inexpensive to install.

Large numbers of users will greatly decrease performance because of high volumes of data traffic.

Ring Allocates access to the network fairly. Adding or removing nodes disables the network.

Performance remains acceptable even with large numbers of users.

Failure of one computer can bring down the entire network. Problems in data transmission can sometimes be difficult to find.

Star Failure of one computer does not affect other computers on the network.

Requires more cable (and possibly higher installation costs) than a bus or ring topology.

Centralized design simplifies troubleshooting and repairs.

The switch is a central point of failure. If it fails, all computers connected to that switch are affected.

Easy to add more computers or groups of computers as needed (high scalability). Performance remains acceptable even with large numbers of users.

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Transmission Media

•  The routes data takes to flow between devices on a network

•  Wired – Twisted pair – Coaxial – Fiber-optic

•  Wireless


Choosing a Cable

•  Maximum run length •  Bandwidth •  Bend radius •  Cable and installation costs •  Susceptibility to interference •  Signal transmission methods


Twisted Pair Cable •  Pairs of copper wire twisted around each other •  Twists make the wires less susceptible to

outside interference •  Two types

–  Shielded twisted pair (STP) –  Unshielded twisted pair (UTP)


Coaxial Cable

•  Four components – Copper core – Nonconductive insulating material – Braided metal – Plastic cover


Fiber-Optic Cable

•  Components include – Glass or plastic fibers – Cladding – Outer jacket

•  Uses light impulses to transmit data

•  Immune to interference


Choosing a Cable •  Maximum run length •  Bandwidth •  Bend radius •  Cable cost

•  Installation costs •  Susceptibility to interference •  Signal transmission methods

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)

24 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall

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Wireless Media 802.11 Standard

•  In business, wireless media are usually add-ons to a wired network

•  Wi-Fi 802.11 standard – 802.11g (54 Mbps) – 802.11n (600 Mbps)


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 SUSE Linux Enterprise


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


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


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 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 29

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 •  Malicious human activity

– Current and former employees hacking or planting viruses

•  Natural events and disasters – Hurricanes, floods, fire


Network Security •  Authentication

–  User ID and password used to access the network –  Use of biometric devices –  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


Network Security

•  Firewalls – Prevent access to the network by

unauthorized users – Composed of software and/or hardware – Router screens and validates data packets – Bastion host acts as proxy server between

internal and external networks – Use network address translation (NAT) to

hide static IP addresses from the Internet


Network Firewall Layout


Summary Questions

•  What are the advantages of an organization network?

•  How does a client/server network differ from a peer-to-peer network?

•  What are the different classifications of client/server networks?

•  What do the various types of dedicated servers do?

Summary Questions •  What are the various network topologies

(layouts or shapes), and why is network topology important in planning a network?

•  What types of transmission media are used in client/server networks?

•  What software needs to be running on computers attached to a client/server network , and how does this software control network communications?

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Summary Questions

•  What components are needed to construct a client/server network?

•  How do network adapters enable computers to participate in a client/server network?

•  What devices assist in moving data around a client/server network?

•  What measures are employed to keep large networks secure?

Participation Question

_________ servers are used to fulfill one specific function and take the load off the main server. A.  Network B.  Dedicated C.  Protocol D.  Peer-to-peer E.  Email


A bus topology: A.  is used most client/server networks. B.  rarely has data collisions. C.  is considered a passive topology. D.  is not affected by a break in the cable. E.  is considered an active topology.

Participation Question If you wish to extend the length of a network without having a signal degrade, you would use a(n): A.  router B.  switch C.  gateway D.  wireless access point E.  repeater


Which of the following is something you would NOT consider when choosing a cable type? A.  Bandwidth B.  Maximum run length C.  Susceptibility to interference D.  Cable radius E.  Bend radius



The purpose of network address translation (NAT) is to ______ . A.  translate IP addresses from the Internet B.  hide user IP addresses from the Internet C.  convert logical ports to physical port

configurations D.  dynamically assign IP addresses via an ISP E.  change the static IP address of the nodes

42 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall

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Computer Networks

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C20 Extra Networks tia7e ch12 ppt - wmich.edu · 2011-08-17 · 8/17/11 2 Classifications of...

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