Chapter 9 - Communications and Networks

Communications

What is computer communications?

°    A process in which one computer transfers data, instructions, and information to another computer(s)

What is needed for successful communications?

What is the primary function of a communications device?

°    To convert or format signals so they are suitable for the communications channel or a receiving device

 

Sending and Receiving Devices

What is a sending and receiving device?

°    Initiates or accepts transmission of data, instructions, and information

What are some specialized sending and receiving devices?

 

Uses of Communications Technologies

What are some uses of communications technology?

°    Communications technology use is all around you

What is voice mail?

°    Allows callers to leave a voice message for the called party

°    Unlike answering machines, voice mail converts an analog voice message into digital form

°    The message is stored in a voice mailbox

°    A voice mailbox is a storage location on a computer in the voice mail system

What is fax?

°    A document transmitted and received over telephone lines

°    Can contain handwritten or typed text, illustrations, photographs, or other graphics

°    You can send or receive a fax using a stand-alone fax machine or a computer fax modem

What is e-mail (electronic mail)?

°     The exchange of text messages and computer files transmitted via a communications network

°     To send and receive e-mail messages, you use e-mail software installed on your computer

What is instant messaging (IM)?

°     A real-time Internet communications service that notifies you when one or more people are online and then allows you to exchange messages or files with them or join a private chat room

What is a chat room?

°    Permits users to converse in real time with each other via the computer while connected to the Internet

°    Types of chat rooms

•    Voice chats

•    Video chats

•    Radio chats

What is a newsgroup?

°    An area on the Web where users conduct written discussions about a particular subject

°    Also called a threaded discussion

°    The difference between a chat room and a newsgroup is that a chat room is a live conversation, and the newsgroup is not

What is Internet telephony?

°    Enables you to talk to other people over the Internet

°    Uses the Internet to connect a calling party and one or more called parties

°    You need Internet telephone software

°    Speak into a a computer microphone

°    Internet telephone software and your computer’s sound card digitize and
compress your
conversation and then
transmit the digitized
audio

What is videoconferencing?

°    Involves using video and computer technology to conduct a meeting between participants at two or more geographically separate locations

°    Requires
computers with
microphones,
speakers, video
cameras, and
communications
devices and
software

What are other conferencing systems?

°    Web conference

•    Conferencing system that uses the Internet, Web browsers, and Web servers to deliver this service

°    Video telephone
call

•    Used by home
users to see
each other as
they talk on
the Internet

What is collaboration?

°    Working with other users connected to a server

°    You can conduct online meetings

•    Allows you to
share
documents
with others in
real time

°    You also can
collaborate via
e-mail

°    Microsoft’s
NetMeeting allows
collaboration

What is groupware?

°    A software application that helps groups of people work together on projects and share information over a network

°    A component of workgroup computing

•    includes network hardware and software that enables group members to work together

°    Most groupware provides personal information manager (PIM) functions

What is a global positioning system (GPS)?

°    Consists of one or more earth-based receivers that accept and analyze signals sent by satellites in order to determine the receiver’s geographic location

What is Digital Angel™?

°    A computer chip containing a GPS device

°    Worn as a bracelet or woven into fabric that has an antenna that communicates with the GPS satellite

°    Measures and sends biological information to the satellite

 

Networks

What is a network?

°    A collection of computers and devices connected by communications channels

°    Facilitates communications among users and allows users to share resources with other users

What is a site license?

°    A legal agreement that allows multiple users to run a software package simultaneously

°    License fee usually is based on the number of users or the number of computers attached of the network

What is a local area network (LAN)?

°     A network that connects computers and devices in a limited geographical area such as a home, school computer laboratory, office building, or closely positioned group of buildings

What is a node ?

°    Each computer or device on a network

What is a network operating system?

°    The system software that organizes and coordinates the activities on a local area network

°    Also called a network OS or NOS

How do some popular operating systems support networks ?

°    Many operating systems have built-in network features

°    In other cases, the network OS is a set of programs that works with another operating system(s)

What is a peer-to-peer LAN?

°     A simple, inexpensive network that typically connects less than 10 computers together

°     Each computer on a peer-to-peer network can share the hardware, data, or information located on any other computer in the network

°     Each computer stores files on its own storage devices

What is a client/server LAN?

°    A network in which one or more computers act as a server and the other computers on the network can request services from the server

What are servers and clients?

°     Server

•     Controls access to the hardware and software on the  network

•     Provides a centralized storage area for programs

•     Dedicated servers perform a specific task

 

Company on the Cutting Edge

°    One of the leading personal computer makers

°    Second-largest computer seller

°    Initial success came from marketing IBM clones,
look-alike computers
that performed like
the IBMs, but were
less costly

 

Networks

What is a wide area network (WAN)?

°    A network that covers a large geographic area using a communications channel that combines many types of media

°    Can be one large network or can consist of two or more LANs connected together

°    The Internet is the world’s largest WAN

What is an Internet use of peer-to-peer (P2P)?

°    An Internet network that enables users with the same networking software to connect to each other’s hard disks and exchange files directly

°    Napster and Gnutella are two examples of P2P

What is a metropolitan area network (MAN)?

°    A backbone network that connects local area networks in a metropolitan area such as a city or town

°    Handles the bulk of communications activity, or traffic, across that region

What is a network topology?

°    The configuration, or physical arrangement, of the devices in a communications network

°    Networks usually use combinations of three topologies

What is a bus network?

°    Consists of a single central cable, to which all computers and other devices connect

°    The bus is the physical cable

°    The bus is also called the backbone

°    Inexpensive and easy to install

What is a ring network?

°    A cable forms a closed ring, or loop, with all computers and devices arranged along the ring

°    Data travels from device to device around the entire ring, in one direction

°    If a device fails, all the devices before the failed device are unaffected, but those after the failed device cannot function

What is a star network?

°    All of the devices connect to a central computer

°    The central computer is called the hub

°    All data that transfers from one computer to another passes through the hub

What are network communications technologies?

°    Specific combinations of hardware and software that allow the different devices on several types of networks to be able to communicate

 

Technology Trailblazer

Robert Metcalfe

°    The inventor of Ethernet

°    Founder of 3Com Corporation

°    Former publisher and a current InfoWorld magazine columnist

°    He realizes the need for computer professionals to communicate their ideas clearly when they speak and write

 

Company on the Cutting Edge

°    Started in 1982 by Scott McNealy and three friends

°    Goal of building engineering workstations in the network computer model

°    The fastest-growing company in history based on revenue and the world’s second most profitable company

°    Builds the technology to power the Internet

 

Networks

What is Ethernet?

°     A LAN technology that allows personal computers to contend for access to the network

°     Based on a bus topology, but can be wired in a star pattern

°     The most popular LAN because it is relatively inexpensive and easy to install and maintain

What is token ring?

°     A LAN technology that controls access to the network by requiring that network devices share or pass a special signal, called a token

°     A token is similar to a ticket

°     The device with the token
can transmit data over
the network

°     Only one token exists
per network

°     Based on a ring topology,
although it can use
a star topology

What is TCP/IP?

°     Short for transmission control protocol/Internet protocol

°     A technology that manages the transmission of data by breaking it up into packets

°     Commonly used for Internet transmissions

What is the Wireless Applications Protocol (WAP)?

°    Allows wireless mobile devices to access the Internet and its services such as the Web and e-mail

°    Uses a client/server network

°    The wireless device contains
the client software, which
connects to the Internet
service provider's
server

°    Devices that support
WAP are called
WAP-enabled devices

What is an intranet?

°     An internal network that uses Internet technologies

°     Generally makes company information accessible to employees and facilitate working in groups

°     Typically also includes a connection to the Internet

What is an extranet?

°    Allows customers or suppliers to access part of a company’s intranet

What is a firewall?

°    A general term that refers to hardware and/or software that restricts access to data and information on a network

What is a home network?

°     Multiple computers connected together in a home or home office

°     All computers in the
house can

•     connect to the
Internet at the
same time

•     access files
and programs
on the other
computers in
the home

•     share
peripherals

What are four types of home networks?

What is an intelligent home network?

°    Extends the basic home network to include features such as lighting control, thermostat adjustment, and a security system

 

Communications Software

What is communications software?

°    Consists of programs that help you establish a connection to another computer or network

°    Manages the transmission of
data, instructions, and
information

°    For two computers to
communicate, they must
have compatible
communications
software

°    Often, separate
communications programs
on your computer each serve
a different purpose

What is the Internet Connection Wizard?

°    A type of communications software that helps you establish a connection to another computer on the Internet using wizards, dialog boxes, and other on-screen messages

How do you access the Internet?

°    Enter a user name and password into a communications software dialog box to connect to an ISP

What is file transfer protocol (FTP)?

°     An Internet standard that allows you to upload and download files to and from a Web server, called the FTP server

°     An anonymous FTP site allows anyone to transfer files

°     Other sites require a specific username and password to access the FTP server

 

The Telephone Network

What is the public switched telephone network (PSTN)?

°    The worldwide telephone system that handles voice-oriented telephone calls

What is a dial-up line?

°    A temporary connection that uses one or more analog telephone lines for communications

°    Not permanent

°    A modem at the sending end dials the telephone number of a modem at the receiving end

What is a dedicated line?

°    A connection that always is established between two communications devices

°    The quality and consistency of the connection is better than a dial-up line because dedicated lines provide a constant connection

What is transfer rate?

°    The speed with which a line carries data and information

°    The faster the transfer rate, the faster you can send and receive data and information

°    Usually are expressed as bits per second (bps)

What are popular types of digital dedicated lines?

°   ISDN

°   DSL

°   T-carrier

°   ATM

What is an ISDN line?

°    Integrated Services Digital Network

°    A set of standards for digital transmission of data over standard copper telephone lines

°    Telephone line can carry three or more signals at once, through the same line using a technique called multiplexing

What is DSL?

°     Digital subscriber line

°     Transmits at fast speeds on existing standard copper telephone wiring

°     Some installations can be used for both voice and data

°     Requires a special network card or DSL modem

°     ADSL (asymmetric digital subscriber line) supports faster transfer rates when receiving data than when sending data

What is a T-carrier line?

°     Any of several types of digital lines that carry multiple signals over a single communications line

°     Uses a technique called multiplexing so that multiple signals can share the telephone line

°     Provides extremely fast data transfer rates

°     Usually only affordable by medium to large companies

What is asynchronous transfer mode (ATM)?

°     A service that carries voice, data, video, and multimedia at extremely high speeds

°     Predicted to become the Internet standard for data transmission

 

Communications Devices

What is a communications device?

°    Any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device

°    Sometimes the device must convert the data, instructions, and information from analog to digital signals or vice versa

What is a modem?

°    A communications device that converts a computer's digital signals to analog signals before they are transmitted over standard telephone lines

°    Sometimes called a dial-up modem

What are internal and external modems?

°    external modem

•    a stand-alone (separate) device

•    attaches to a special serial
port on a computer

•    a standard telephone cord
connects to a telephone outlet

°    Internal modem

•    A card that you insert into an expansion slot on a computer's motherboard

•    A standard telephone cord attaches between a port on the modem
and the telephone outlet

What is a digital modem?

°    One that sends and receives data and information to and from a digital telephone line such as ISDN or DSL

What is a cable modem?

°    A modem that sends and receives data over the cable television (CATV) network

°    Currently much
faster than a
dial-up modem
or ISDN

°    Usually attaches
to a USB port or
a port on a
network interface
card

What is a network interface card (NIC)?

°    Also called a LAN adapter

°    A card you insert into an expansion slot of a personal computer or other device, enabling the device to connect to a network

°    Works with a particular network technology

°    Available for desktop and mobile computers

What is a hub?

°    A device that provides a central point for cables in a network

 

Communications Channel

What is a channel?

°    The communications path between two devices

What is a typical communications channel?

What are characteristics of transmission media?

 

Physical Transmission Media

What is physical transmission media?

°    Wire, cable, and other tangible (touchable) materials used to send communications signals

What is twisted-pair cable?

°    Consists of one or more twisted pair wires bundled together

°    Each twisted pair
wire consists of
two separate
insulated copper
wires

°    Twisted together
to reduce noise

°    Noise is an
electrical
disturbance that
can degrade
communications

What is coaxial cable?

°    Consists of a single copper wire surrounded by at least three layers

°    Often called
coax

°    Often used
for cable
television
wiring

What is fiber-optic cable?

°    Contains a core of dozens or hundreds of thin strands of glass or plastic

°    Uses light to transmit signals

°    Each strand
is called an
optical fiber

•    Thin as
a human
hair

What are the advantages  and disadvantages of fiber-optic cable?

 

Wireless Transmission Media

What is wireless transmission media?

°    Send communications signals through the air or space

°    Used when it is inconvenient, impractical, or impossible to install cables

What is broadcast radio?

°    A wireless transmission medium that distributes radio signals through the air over long distances such as between cities, regions, and countries and short distances such as within an office or home

°    Slower and more susceptible to noise than physical transmission media

What is Bluetooth™?

°    Uses short-range radio waves to transmit data among Bluetooth™-enabled devices

°    Device contains
a small chip that
allows it to
communicate
with other
Bluetooth™-
enabled devices

What is an example of a wireless local area network?

What is cellular radio?

°    A form of broadcast radio that is used widely for mobile communications, specifically wireless modems and cellular telephones

°    A cellular telephone
is a telephone
device that uses
radio signals to
transmit voice and
digital data
messages

What is Personal Communications Services (PCS)?

°     A set of technologies used for completely digital cellular devices

°     Include handheld computers, cellular telephones, pagers, and fax machines

°     Devices have wireless modems allowing you Internet access and e-mail capabilities

What are microwaves?

°    Radio waves that provide a  high-speed signal transmission

°    Involves sending signals from one microwave station to another

What is a microwave station?

°    An earth-based reflective dish that contains the antenna, transceivers, and other equipment necessary for microwave communications

°    Uses line-of-sight transmission

•    Must transmit in a straight line with no obstructions between microwave antennas

What is a communications satellite?

°    A space station that receives microwave signals from an earth-based station, amplifies the signals, and broadcasts the signals back over a wide area to any number of earth-based stations

°    Transmission to a
satellite is an uplink

°    Transmission from a
satellite to an
earth-based station
is a downlink

What is infrared (IR)?

°    A wireless transmission media that sends signals using infrared light waves

°    Requires a line-of-sight transmission

°    Many computers and devices have an IrDA port that enables the transfer of data using infrared light rays

 

Summary of Communications and Networks

°    Communications

°    Sending and receiving devices

°    Uses of communications technologies

°    Networks

°    Communications software

°    The telephone network

°    Communications devices

°    Communications channel

°    Physical transmission media

°    Wireless transmission media

Chapter 9 Complete