Using Information Technology Telecommunications. 2 The term telecommunication means communication at...
-
Upload
derick-hoover -
Category
Documents
-
view
221 -
download
0
description
Transcript of Using Information Technology Telecommunications. 2 The term telecommunication means communication at...
Using Information Technology
Telecommunications
Tele
com
mun
icatio
ns
2
Telecommunications The term telecommunication means
communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable.
Tele
com
mun
icatio
ns
3
WHAT IS A NETWORK? A network is simply two or more
computers that are linked together. The most common types of networks are:
Local Area Networks (LANS) Metropolitan Area Networks (MANS) Wide Area Networks (WANS).
Tele
com
mun
icatio
ns
4
Types of NetworksMetropolitan area network (MAN) - a communications network covering a city or a suburb
Local area network (LAN) - connects computers and devices in a limited geographical area
Tele
com
mun
icatio
ns
5
Types of Networks Wide area network (WAN) - a communications network that
covers a wide geographical area, such as a country or the world
Tele
com
mun
icatio
ns
6
BENEFITS OF A NETWORKS Information sharing: Authorized users
can use other computers on the network to access and share information and data. This could include special group projects, databases, etc.
Hardware sharing: One device connected to a network, such as a printer or scanner, can be shared by many users.
Tele
com
mun
icatio
ns
7
BENEFITS OF A NETWORKS Software sharing: Instead of purchasing
and installing a software program on each computer, it can be installed on the server. All of the users can then access the program from a single location.
Collaborative environment: Users can work together on group projects by combining the power and capabilities of diverse equipment.
Tele
com
mun
icatio
ns
8
COMMUNICATIONS MEDIA Communications Channel
To transfer data from one computer to another requires some type of link through which the data can be transmitted. This link is known as the communications channel.
To send data through the channel requires some type of transmission media, which may be either physical or wireless.
Tele
com
mun
icatio
ns
9
Wired Communications Channels Twisted-pair -cable - consists of two
independently insulated wires twisted around each other (least expensive type of cable—the kind that is used in many telephone systems)
Tele
com
mun
icatio
ns
10
Wired Communications Channels Coaxial cable - insulated copper wire wrapped in a solid
or braided metal shield, then in an external cover (the primary type of cabling used by the cable television industry; it is more expensive than twisted pair)
Tele
com
mun
icatio
ns
11
Wired Communications Channels Fiber-optic cable - dozens or hundreds of thin
strands of glass or plastic that transmit pulsating beams of light rather than electricity
Tele
com
mun
icatio
ns
12
Characteristics Of Cables Twisted-pair wire
characteristics:• Slow.• Does not protect well
against electrical interference.
• Prevalent! Used extensively in telephone lines.
Coaxial cablecharacteristics:• Better than twisted-pair
wiring at resisting noise.• Carries voice & data at
faster rate than twisted-pair.
• Widely used in cable television.
Tele
com
mun
icatio
ns
13
Characteristics Of Cables
Fiber-optic cable characteristics:• Unaffected by random electromagnetic
interference• Lighter and more durable than twisted-pair
& co-ax cable
Tele
com
mun
icatio
ns
14
Wireless Communications Channels Infrared transmission - the transmission
of data signals using infrared-light waves
Tele
com
mun
icatio
ns
15
Wireless Communications Channels Broadcast radio - a
wireless transmission medium that sends data over long distances--between regions, states, or countries
Microwave radio - transmits voice & data through the atmosphere as super-high-frequency radio waves called microwaves
Tele
com
mun
icatio
ns
16
Short-Range Wireless Communications
Bluetooth - a short-range wireless digital standard aimed at linking cellphones, PDAs, computers, & peripherals up to distances of 30 feet
WiFI - a short-range wireless digital standard aimed at helping machines inside offices to communicate at high speeds and share Internet connections at distances up to 300 feet
HomeRF - a separate, incompatible standard designed to network up to 10 PCs & peripherals as far as 150 feet apart
Tele
com
mun
icatio
ns
17
Factors Affecting How Data Is Transmitted Transmission rate - a function of two variables:
Frequency - the cycles of waves per second
Bandwidth - the range between the highest & lowest frequencies
Higher frequency => greater transmission rate Larger bandwidth => greater transmission rate
Tele
com
mun
icatio
ns
18
Factors Affecting How Data Is Transmitted Line configurations
Point-to-point line - directly connects the sending & receiving devices
Multipoint line - a single line that interconnects several communications devices to one computer
Tele
com
mun
icatio
ns
19
Factors Affecting How Data Is Transmitted Serial vs. parallel
transmission
Serial data transmission - bits are transmitted sequentially, one after the other
Tele
com
mun
icatio
ns
20
Factors Affecting How Data Is Transmitted
Serial vs. parallel transmission Parallel data transmission - bits are transmitted through separate lines simultaneously
Tele
com
mun
icatio
ns
21
Factors Affecting How Data Is Transmitted Direction of
transmission: simplex, half-duplex, & full-duplex
Simplex transmission - data can travel in only one direction
Tele
com
mun
icatio
ns
22
Factors Affecting How Data Is Transmitted
Direction of transmission: simplex, half-duplex, & full-duplex
Half-duplex transmission - data travels in both directions but only in one direction at a time
Tele
com
mun
icatio
ns
23
Factors Affecting How Data Is Transmitted
Direction of transmission: simplex, half-duplex, & full-duplex
Full-duplex transmission - data is transmitted back and forth at the same time
Tele
com
mun
icatio
ns
24
Factors Affecting How Data Is Transmitted
Asynchronous transmission - data is sent one byte at a time, with each string of bits making up the byte bracketed with special control bits
Transmission mode: asynchronous vs. synchronous
Tele
com
mun
icatio
ns
25
Factors Affecting How Data Is Transmitted
Synchronous transmission - data is sent in blocks, with start and stop bit patterns (synch bytes) at the beginning and end of the blocks
Transmission mode: asynchronous vs. synchronous
Tele
com
mun
icatio
ns
26
Factors Affecting How Data Is TransmittedCircuit switching - transmitter has full use of the circuit until all the data has been transmitted and the circuit is terminated
Packet switching - electronic messages are divided into packets for transmission over a wide area network to their destination through the most expedient route
Tele
com
mun
icatio
ns
27
Factors Affecting How Data Is Transmitted
Multiplexers: a device that merges several low-speed transmissions into one high-speed transmission.
Concentrators: collects data in a temporary storage area.
Front-end processors: a smaller computer that is connected to a larger computer and assists with communications functions.
Tele
com
mun
icatio
ns
28
HOW ARE NETWORKS CATEGORIZED? Networks are usually classified
using three properties: Topology Protocol Architecture
Tele
com
mun
icatio
ns
29
Topology of LANs Bus network - one in
which all communications devices are connected to a common channel
Tele
com
mun
icatio
ns
30
Topology of LANs Ring network - one in
which all microcomputers and other communications devices are connected in a continuous loop
Tele
com
mun
icatio
ns
31
Topology of LANs Star network - one in which all microcomputers and other
communications devices are connected to a central server
Tele
com
mun
icatio
ns
32
NETWORK/COMMUNICATION PROTOCOLS Protocol - a set of
conventions governing the exchange of data between hardware and/or software components in a communications network
Tele
com
mun
icatio
ns
35
Types of LANS Peer-to-peer LAN - all microcomputers on the
network communicate directly with one another without relying on a server
Tele
com
mun
icatio
ns
36
Types of LANS Client/server LAN:
Clients - microcomputers that request data; and
Server - a powerful microcomputer that manages shared devices
Tele
com
mun
icatio
ns
37
NETWORKING HARDWARE AND SOFTWARE
Hub – electronic device (with a number of ports) used in a LAN to link groups of computers
Repeaters (also called amplifiers) – electronic devices that receive signals and amplify and send them along the network
Routers - electronic devices used to ensure messages are sent to their intended destinations
Tele
com
mun
icatio
ns
38
NETWORKING HARDWARE AND SOFTWARE
Gateway – consists of hardware and/or software that allows communications between dissimilar networks
Bridge – consists of hardware and/or software that allows communication between two similar networks
Tele
com
mun
icatio
ns
39
Intranets, Extranets, & Firewalls
Intranet- an organization’s internal private network that uses the infrastructure and standards of the Internet and the WWW
Extranets - private intranets that connect not only internal personnel but also selected suppliers and other strategic parties
Firewalls - a system of hardware and software that blocks unauthorized users inside and outside the organization from entering the intranet