Transcript Networks and Communications

Networks
and
Communications
Telecommunications
Use of hardware and software to
send and receive information over
communications media.
Allows computer users throughout
the world to communicate with
one another.
Data Transmission
Characteristics
Analog or Digital
(Type of Signal)
Serial or Parallel
(Order of Bits)
Analog/Digital Transmission
Digital signals are sent as bits (0,1).
Analog signals take the form of continuous waves
transmitted over a medium at a certain frequency
range. Changes in the wave transmission reflect
changes in voice and sound pitch.
Digital Transmission
Digital Signal
Computers use binary numbers (0,1) to transform data
into digital signals.
Modems
Converts digital signals into analog signals, so they can be
sent over telephone lines.
“Modem” is derived from Modulate and Demodulate.
Modulation refers to the process of changing a digital signal
into an analog signal.
Demodulation refers to the process
of changing an analog signal into a
digital signal.
Parallel Transmission
A group of 8 bits representing a
single byte (plus 1 bit called a
parity bit) are transmitted at the
same time over 9 separate paths.
Computers are equipped with
parallel and serial ports to
connect modems, printers and
mice.
Serial Transmission
Serial transmission is slower than parallel.
All the bits (0s and 1s) that comprise the data are
transmitted one bit after another in a continuous line.
Communications Media
Point To Point
A physical link that allows computers to
be connected to other computers in
different locations.
Either wired or wireless
LAN Cabling
Twisted Pair Cable consists of
two wires that are independent,
insulated, and twisted around
each other.
Coaxial cable consists of an
insulated-center wire
grounded by a shield of
braided wire.
Fiber Optic Cable
Contains hundreds of clear fiberglass
or plastic fibers (threads).
Communication Bandwidth
Bandwidth
Rate of transmission over the medium.
Measured in bits per second (bps).
Broadband
Communications medium capable of carrying a
large amount of data at faster speeds.
Narrowband
A communications medium carrying smaller
amounts of data.
T- Carrier Lines
Extremely high speed dedicated connections between 2 points.
PSTN = Public Service Telephone Network
CSU/DSU = Channel Service Unit/
Digital Service Unit
Provide for communication over the PSTN.
ISDN Line
Special digital
telephone line that
transmits and
receives information
at very high speeds.
Wireless Communication
Wireless media transmit information as
electromagnetic signals through the air.
Microwaves
Infrared Technology
Cellular Technology
Satellite Systems
Microwave Systems
Transmit data through the
atmosphere from one
microwave station to
another.
Also transmit from a
microwave station to a
satellite and then back
to earth to another
microwave station.
Communications Satellite
Solar powered
device containing
small, specialized
radios called
transponders.
Transponders receive signals from
transmission devices on the
ground called earth stations.
Geosynchronous Orbits
In geosynchronous orbits, satellites circle the
earth at the same speed as the earth’s rotation.
Cellular Technology
Allows people to communicate
wirelessly to and from anywhere
in the world.
Contact is maintained with
cellular antennae.
Each area, called a cell,
has its own antennae
encompassing a circular
space of 10-12 square
miles in diameter.
Infrared Technology
Transmits data in the form of infrared light waves is transmitted from a special
port in laptop to an infrared sensor on the printer.
Network Classifications
Network Architecture
Refers to the way a network is
designed or built.
Client/Server
Peer-to-Peer
Client/Server Architecture
Information is sent from a
client computer to a server.
The server relays information
back to the client or to other
computers on the network.
Peer- to-Peer
Each PC workstation has
equivalent capabilities and
responsibilities.
Network Design
Network Topology (Layout)
Refers to the way computers and peripherals are
configured to form networks.
Bus Topology
All computers are linked by a single line of cable.
Star Topology
Multiple
computers and
peripheral devices
are connected to
a central
computer or host.
Network Topology
(Continued)
Ring Topology
Each computer or
workstation is
connected to two
other computers with
the entire network
forming a circle.
Hybrid Technologies
Combine different links.
Wide Area Network (WAN)
A WAN spans a large geographical area and connects networks
such as metropolitan area networks, public access networks,
value added networks, and virtual private networks together.
Local Area Network (LAN)
A LAN is a private network that connects
PCs or workstations located in close
proximity.
Intranet
Access to an
intranet Web site is
restricted by a
firewall.
An intranet is accessible only by a business or organization, its
members, employees or authorized users.
Extranet
An extranet makes
specific information
available to users within
the organization and
other information
available to outsiders.
Often companies share
information with their
business partners or
customers using an
extranet.
Networking Communications
Hardware and Software
Hub
An electric device used
in a LAN to link groups
of computers.
Repeaters/Amplifiers
Electric devices that receive signals and amplify
and send them along the network.
Concentrator
Transmits data from only 1 device at a time over the channel.
Internetworking Device
Routers
Electronic devices used to
ensure messages are sent to
their intended destination.
Connecting Networks Together
Bridge
Consists of hardware and/or software
that allows communication between
two similar networks.
Multiplexer
Electronic device that allows low speed
devices to simultaneously share a single high
speed communications media.
Connecting Dissimilar Networks
Gateways
Consists of hardware and/or
software that allows
communication between two
dissimilar networks.
Communications Software
Allows computers to connect to access and use the network
resources. E-mail software is used to send and receive electronic
messages using the internet.
Connecting Clients
to a Network
Web Browsers
Allows users to access and
view Web pages.
Groupware
Allows groups of people
on a network to share
information and to
collaborate on various
projects.
Communications Protocol
Protocol : A set of rules and procedures for
exchanging information between network devices and
computers.
Directional Protocols
Determine the directional flow of
transmission among devices.
Directional Protocols
Direction method can be simplex,
half-duplex, and full-duplex.
Asynchronous Transmission
Data sent by protocols are transmitted at
irregular intervals using start and stop bits.
Synchronous Transmission
Blocks of bytes are wrapped in start
and stop bytes called synch bits.
TCP/IP
Transmission Control Program/ Internet Protocol
Governs how packets are constructed and
sent to their destinations.
File Transfer Protocol (FTP).
Large files can be
transmitted and received.
(HTTP)
Hypertext Transfer Protocol
The World Wide Web (WWW) is
used to transfer Web pages to
computers.
Mail Transfer Protocols
(POP) Post
Office Protocol
Allows recipient to
retrieve messages.
(SMTP) Simple Mail
Transfer Protocol
Messages are transmitted using Simple
Mail Transfer Protocol.
Wireless Application
Protocol (WAP)
Enables wireless devices to
access and use the internet
using a client/server network.
In 1997, the Institute of
Electrical and Electronic
Engineers (IEEE) approved a
new protocol for wireless LAN
technology called
802.11 (Wi-Fi).
On the Horizon
INCREASED BANDWIDTH AVAILABILITY
• Free-space optics, a nascent technology that uses lasers to send optical
signals through the air
• Dense wave division multiplexing (DWDM)
HIGHER-SPEED OPTICAL FIBERS
• A single strand of fiber thinner than a human hair can carry every phone call
and e-mail in the world
• Hollow fiber—the next wave in fiber-optic cable
BEAMING DATA
• Infrared transmission represents tremendous potential for the future.
• Data traveling through space in the form of infrared light can move faster
than radio waves, and with potentially less interruption.