Technology in Action Chapter 12

Technology in ActionTechnology in Action

Chapter 12Chapter 12

Behind the Scenes: Networking and Behind the Scenes: Networking and Security in the Business WorldSecurity in the Business World

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

Chapter TopicsChapter Topics

• 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


Chapter Topics (cont.)Chapter Topics (cont.)

• Types of transmission media

• Network software

• Network adapters

• Moving data in a client/server network

• Securing networks


Networking AdvantagesNetworking Advantages• Networks

Increase productivity Enable the sharing of hardware resources Facilitate knowledge sharing

serve the needs of many people at one time

Enable the sharing of softwarecan access the same copy of a program from the server

Facilitate Internet connectivity Enable enhanced communication


Client/Server NetworksClient/Server Networks

• Server is a computer that both stores and shares resources on a network

• Data flows efficiently

• Servers respond to requests from large number of clients at a time


Client/Server NetworksClient/Server Networks

• Servers perform specific tasks• Scalable- added easily without affecting added easily without affecting

the performance of the other network the performance of the other network • Centralized

– clients connect to a

server that performs

tasks for them


Classifications of Classifications of Client/Server NetworksClient/Server Networks

Network Architecture

It is classified according to how it being controlled and distance between nodes

• 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



• PAN– Personal area network– Used to connect wireless devices ( Bluetooth-

enabled devices) in close proximity to each other

• Intranet– Private network set up by entity used exclusively by

select group of individuals(employees, customer )– not accessible to nonemployees– Protected from the Internet by a firewall



• Extranetspieces of intranets that only certain corporations or individuals can accessUseful for enabling electronic data interchange(EDI)- access to inventory databases and sharing information(partners or industry trade).Use virtual private networks(VPN) for security(VPN) uses the public Internet communications infrastructure to build a secure, private network between various locations.


Constructing Constructing Client/Server NetworksClient/Server Networks

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1. Servers2. Network topologies3. Transmission media4. Network adapters5. Network navigation

devices6. Network operating

system software

1. Servers 1. Servers

• The number and types of servers depend on network size and workload


1.Servers 1.Servers • Dedicated servers

– Perform one specific function

• Authentication servers– Keep track of network logins and services

available, act as overseers for the network. – manage and coordinate the services provided

by any other dedicated servers located on the network.

• File servers– Store and manage files for network user


1.Servers1.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, outgoing and internal e-mail


1.Servers1.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


2. Network Topologies2. Network Topologies

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

• Types of network topologies1) Bus

2) Ring

3) Star

4) Hybrid


2. Network Topologies:2. Network Topologies:Bus TopologyBus Topology

• All nodes are connected in sequence on a single cable• Each computer on a bus network can communicate with every other computer on the network

directly. • One computer transmits data at a time• Limitation- data collisions occur easily if two computers transmit data at the same time• cap of by terminator ( device that absorbs a signal)


2. Network Topologies : 2. Network Topologies : Ring TopologyRing Topology

• Nodes are laid out in a circle / ring

• A token (data packet) flows in one direction from device to device

• data transfer rates of up to 100 Mbps

• Performance remain acceptable in large number of user

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• Failure of one computer can bring down the entire network.

2. Network Topologies: 2. Network Topologies: Star TopologyStar 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


2. Network Topologies:2. Network Topologies:Comparing TechnologiesComparing Technologies

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Topology Advantages Disadvantages

Bus

Uses a minimal amount of cabling.

Easy, reliable, and inexpensive to install.

Breaks in the cable can disable the network.

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

Ring

Allocates access to the network fairly.

Performance remains acceptable even with large numbers of users.

Adding or removing nodes disables the network.

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.

Centralized design simplifies troubleshooting and repairs.

Easy to add more computers or groups of computers as needed (high scalability).

Performance remains acceptable even with large numbers of users.

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

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

Avoiding Data CollisionsAvoiding Data Collisions on an Ethernet Network on an Ethernet Network


Avoiding Data CollisionsAvoiding Data Collisions on an Ethernet Network on an Ethernet Network

• Star networks are Ethernet networks, to avoid data Star networks are Ethernet networks, to avoid data collisions: collisions: CSMA/CDCSMA/CD ( Carrier Sense Multiple Access with ( Carrier Sense Multiple Access with Collision Detection). Collision Detection).

• With CSMA/CD, (has carrier sense) to determine that no With CSMA/CD, (has carrier sense) to determine that no other nodes are currently transmitting data signals. other nodes are currently transmitting data signals.

• node doesn’t hear any other signals, it assumes it is safe to node doesn’t hear any other signals, it assumes it is safe to transmit data. transmit data.

• When two signals collide, a node on the network detects the When two signals collide, a node on the network detects the collision. Sends a special signal, (jam signal) to all network collision. Sends a special signal, (jam signal) to all network nodes, alerting them that a collision has occurred. nodes, alerting them that a collision has occurred.

• The nodes then stop transmitting and wait a random amount The nodes then stop transmitting and wait a random amount of time before retransmitting their data signals. of time before retransmitting their data signals.

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3. Transmission Media3. Transmission Media

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

• Wired – Twisted pair– Coaxial– Fiber-optic

• Wireless


3. Transmission Media : 3. Transmission Media : Choosing a CableChoosing a Cable

• Maximum run length- Each type of cable has a maximum run length over which signals sent across

• Bandwidth - amount of data that can be transmitted across a transmission medium in a certain amount of time

• Bend radius- how many degrees a cable can be bent in a 1-foot segment before it is damaged

• Cable and installation costs - cost per foot of different types and grades of cable varies widely

• Susceptibility to interference- Signals traveling down a cable are subject to interference

• Signal transmission methods

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3. Transmission Media : 3. Transmission Media : Twisted Pair CableTwisted Pair Cable

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• Pairs of copper wire twisted around each other and covered by a protective jacket (or sheath).

• Twists make the wires less susceptible to outside interference

• Two typesa) Unshielded twisted

pair (UTP)

b) Shielded twisted

pair (STP)

3. Transmission Media : 3. Transmission Media : Coaxial CableCoaxial Cable

• Coaxial cable is the cable used with cable TV• Four components

– Copper core– Nonconductive insulating material– Braided metal– Plastic cover


3. Transmission Media : 3. Transmission Media : Fiber-Optic CableFiber-Optic Cable

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

• Uses light impulses to transmit data

• Immune to interference


•Composed of a glass fiber (bundle of fibers)

3. Transmission Media : 3. Transmission Media : Wireless Media 802.11 StandardWireless Media 802.11 Standard

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

• Wi-Fi 802.11 standard– 802.11g– 802.11n


4.Network Operating 4.Network Operating Systems (NOS)Systems (NOS)

• Needs to be installed on each client computer and server connected to the network to provide the services necessary for them to communicate.

• 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

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5. Network Adapters5. Network Adapters• Devices that enable computers to communicate on

a network• Network interface cards (NICs)• Three functions

1.1.They generate high-powered signals to enable network They generate high-powered signals to enable network transmissions. transmissions.

2.2.They break the data down into packets and prepare them They break the data down into packets and prepare them for transmission across the network. for transmission across the network.

3.3.They act as gatekeepers for information flowing to and They act as gatekeepers for information flowing to and from the client computer. from the client computer.

• Ethernet compliant• Wireless NICs

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6. Network Navigation Devices6. 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– MAC addresses help enhance network

security.


Network Navigation DevicesNetwork Navigation Devices

Repeaters– Amplify a signal and

retransmit it– do not transmit signals to do not transmit signals to

specific devices; they just specific devices; they just forward them along the forward them along the media.media.

Hubs– Transmit signals; have

multiple ports• Receive a signal from a

device• Reconstruct the signal• Transmit the signal to

all ports on the hub

Switches and bridges– Send data on a specific route

through the network

• A A switchswitch viewed as a “smart” hub. viewed as a “smart” hub. It makes decisions, based on the It makes decisions, based on the MAC address MAC address ((Physical address of

network adapter) of the data, as to ) of the data, as to where the data is to be sent. where the data is to be sent.

Routers– Send information between

two networks

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6. Network Navigation Devices6. Network Navigation Devices• Repeaters

– Amplify a signal and retransmit it– Extend cable runs– do not transmit signals to specific devices; they just forward

• Hubs– Transmit signals; have multiple ports• Receive a signal from a device• Reconstruct the signal• Transmit the signal to all ports on

the hub33

6. Network Navigation Devices6. Network Navigation Devices

• Switches and bridges– Send data on a specific

route through the network– Switch - based on the

MAC address of the data, as to where the data is to be sent

– Bridges send data between different collision domains

• Routers– Send information

between two networks

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Network Security ThreatsNetwork Security Threats

• Human errors and mistakes

- Mistakes of input or deletion

• Malicious human activity– Current and former employees hacking or

planting viruses

• Natural events and disasters– Hurricanes, floods, fire


Network SecurityNetwork Security• Authentication

– User ID and password used to access the network– Use of biometric devices– Use of a possessed object for access (identification badges,

magnetic key cards, and smart keys.)

• Access privileges– Enable access to certain network systems – Activity can be tracked to a specific user.

• Physical protection measures– Restrict physical access to sensitive network equipment– Magnetic card readers– Biometric access devices

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Network SecurityNetwork Security

• Firewalls– Prevent access to the network by unauthorized users– Composed of software and/or hardware– work as packet screeners. Packet screening involves

examining incoming data packets to ensure they originated from or are authorized by valid users on the internal network

– Bastion host/proxy server

A proxy server acts as a go-between for computers on the internal network and the external network (the Internet)


Network Firewall LayoutNetwork Firewall Layout


Chapter 12 Summary QuestionsChapter 12 Summary Questions

1. What are the advantages of a business network?

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

3. What are the different classifications of client/server networks?



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

5. What do the various types of servers do?

6. What are the various network topologies (layouts), and why is network topology important in planning a network?



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

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


Chapter 12 Summary QuestionsChapter 12 Summary Questions9. How do network adapters enable

computers to participate in a client/server network?

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

11.What measures are employed to keep large networks secure?


Technology in Action Chapter 12

Documents

performance

bridges send

avoiding data

multiple ports

clientserver

transmit signals

clientserver

large numbers