Computers Are Your Future

greydullNetworking and Communications

Oct 30, 2013 (3 years and 9 months ago)

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Computers Are
Your Future

© 2005 Prentice
-
Hall, Inc.

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
2

Computers Are Your Future

Chapter 6


Networks: Communicating and

Sharing Resources



Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
3

What You Will Learn About


Basic networking concepts


The three major types of physical media


Bandwidth


How modems transform digital computer signals into
analog signals


Circuit switching and packet switching networks

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
4

What You Will Learn About


The importance of protocols in a computer network


The advantages of a network


Peer
-
to
-
peer and client/server LANs


The most widely used LAN protocol


Ways that businesses use WANs


Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
5

Network Fundamentals


A computer
network

consists of
two or more computers linked
together to exchange data and
share resources.


Communications

is the process
of sending and receiving
messages.


Communications channels

are
the paths through which messages
are passed.


Communications devices

transform electronic signals.

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
6

Physical Infrastructure

Physical infrastructure refers to cables, modems, switches,
and routers.


Twisted
-
pair



Two insulated wires twisted around each other;
the same type of wire as that used for telephones


Types of twisted
-
pair technologies:


Leased line (T1)


Integrated Services Digital Network (ISDN)


Digital Subscriber Line (DSL)


Coaxial cable



Consists of an insulated center wire
surrounded by a layer of braided wire; the same type of wire as
that used for cable TV


Fiber
-
optic cable



Type of fiber glass cable that transmits
data in the form of light impulses; can carry more data for
longer distances than other wire

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
7

Bandwidth


Bandwidth

is the amount of data that can be
transmitted through a communications channel.


Digital bandwidth is measured in bits per second
(bps), kilobits per second (Kbps), megabits per
second (Mbps), or gigabits per second (Gbps).


For example, low bandwidth could be 56 Kbps and
high bandwidth could be 622 Mbps.

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
8

Modulation

Digital

Analog

Analog

Digital

Demodulation

Modems: From Digital to Analog and Back


Modems

are devices that transform signals when sending
and receiving transmissions.


Modulation



Transforming digital signals to analog


Demodulation



Transforming analog signals to digital

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
9

Internal Modem

External Modem

Modems: From Digital to Analog and Back


Two types of modems:


Internal modems



Fit into a computer’s expansion slot


External modems



Connect to a port outside the system
box

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
10

Asynchronous and Synchronous
Communications


Asynchronous communication

is a method of
networking in which bits of data are sent and
received one bit at a time; each byte contains a start
and stop bit.


Synchronous communication

requires a
synchronization signal that identifies units of data.

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
11

Modulation Protocols


Modulation protocols

are communications standards
that modems conform to.


Data transfer rate

is the rate at which two modems
can exchange data. It is measured in bits per second
(bps).


A modulation protocol called
V.90

enables modems
to transfer data at 56 Kbps.

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
12

Cable Modems


Cable modems

enable computers to access the
Internet by way of a cable TV connection.


Data is transferred through a coaxial cable.


Bandwidths range from 500 Kbps to well over 1
Mbps.


Bandwidth is divided among the number of
subscribers using it.


Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
13

Circuit switching


Networks create an end
-
to
-
end circuit between the
sending and receiving
computers.


Electronic switches
establish and maintain the
connection.

Switching and Routing Techniques

Packet switching


Outgoing messages are
divided into fixed
-
size
data units called packets.


Packets are numbered and
addressed to the receiving
computer.


Routers examine the
packets and send them to
their destination.


Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
14

Advantages

Disadvantages

Circuit switching

Voice and real
-
time
transmission

No delivery delays

Costly

A direct electrical
connection between the
computers is required

Packet switching

Efficient, less
expensive, and reliable

Will function if part of
the network is down

Delays in receiving
packets

Not ideal for real
-
time
voice communication

Advantages and Disadvantages of Circuit and
Packet Switching

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
15

Protocols


Protocols

are fixed, formalized standards that specify
how computers can communicate over a network.


Protocol suite



The total package of protocols that
specify how a network functions

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
16

Network Layers


Network architecture is the overall design of a network.


The network design is divided into layers, each of which
has a function separate from that of the other layers.


Protocol stack



The vertical (top to bottom) arrangement
of the layers; each layer is governed by its own set of
protocols

user

physical media

user

physical media

receiving

sending

protocol

layer

stack

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
17


Reduced hardware costs


Users share equipment

Connected people


People can work
together without being
at the same location


Groupware enables
sharing of schedules
and communications

Advantages of Networking

Shared applications


Users share software


File server enables all
users to work with the
same application program

Building information
resources


Users create common
pools of data that can be
accessed by employees


Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
18


Local Area Network (LAN)


Links computers within a
building or group of
buildings


Uses direct cables, radio, or
infrared signals


Types of Computer Networks

Wide Area Network (WAN)


Links computers separated
by a few miles or thousands
of miles


Uses long
-
distance
transmission media


Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
19

Local Area Networks (LANs)


Network access is controlled by a network administrator.


Users can access software, data, and peripherals.



LANs require special hardware and software.


Computers connected to a LAN are called
workstations

or
nodes
.


Types of LANs:



Peer
-
to
-
peer



Client
-
server

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
20

LAN Hardware and Software

Networking Hardware


Network interface card

(
NIC
)


Provides the
connection between the
computer and the network


Inserted into a computer

s
expansion slot

Networking Software


Operating system that
supports networking
(Unix, Linux, Windows,
Mac OS)


Additional system
software

NIC

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
21

Peer
-
to
-
Peer Networks


All computers on the network are treated as equal.


There are no file servers.


Users decide which files and peripherals to share.


Peer
-
to peer is not suited for networks with many
computers.


Peer
-
to
-
peer is easy to set up. Example: home
networks

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
22

Client
-
Server Networks


Typical corporate networks are
client
-
server
.


Client
-
server requires various topologies or physical layouts.


The network requires file servers, networked computers
(clients), and a network operating system (NOS).


Clients send requests to servers for programs and data, and
to access peripherals.

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
23

LAN Topologies


The physical layout of a LAN is called its
topology
.


Topologies resolve the problem of
contention
, which
occurs when multiple users try to access the LAN at the
same time.


Collisions or corrupt data occur when different computers use
the network at the same time.

Bus topology


Called a daisy chain


Every workstation is connected to a
single cable


Resolves collisions through
contention management


Difficult to add workstations

Star topology


Contains a hub or central wiring
concentrator


Easy to add workstations


Resolves collisions through
contention management


Ring topology


All workstations are attached in a
circular arrangement


A special unit of data called a

token

travels around the ring


Workstations can only transmit data
when they possess a token

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
24

Wide Area Networks (WANs)


WANs

are similar to long
-
distance telephone systems.


They have a local access number called a
point of presence

(
POP
).


They contain long
-
distance trunk lines called
backbones
.

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
25

WAN Applications

LAN
-
to
-
LAN


WANs are used to connect
LANs at two or more
geographic locations.


Companies use WANs to
connect their branches to
one network system.

Transaction Acquisition


Information about
transactions is instantly
relayed to the corporate
headquarters.


Point
-
of
-
sale

(
POS
)
terminals relay
transactions to central
computers through WANs.

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
26

Backbones


Backbones
, high
-
capacity transmission lines, are
regional, continental, or transcontinental.


Internet backbones can carry 2.5 gigabits of data per
second.

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
27

Chapter 6 Summary


Computer networks link two or more computers to exchange
data and share resources.


Two types of computer networks:


Local area network (LAN)


Wide area network (WAN)


Computer networks:


Reduce hardware costs


Enable users to share applications


Provide a means to pool an organization’s data


Foster teamwork


Computer networks require physical media such as telephone
wire, coaxial cable
,

or fiber
-
optic cable to connect the
computers.

Computers Are Your Future Chapter 6

© 2005 Prentice
-
Hall, Inc

Slide
28

Chapter 6 Summary continued


Modems transform analog and digital signals.


Network protocols enable the network to function smoothly.


Data is sent through the network by switching and routing
techniques.


LAN topologies include:

Bus topology

Star topology

Ring topology


Wide area networks are used to link computers throughout the
world.