Transcript Networks and Telecommunications

INFORMATION TECHNOLOGY
Networks and
Telecommunications
Learning Outcomes
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Summarize the individual components of a
computer network
Describe the three main network topologies
Explain the difference between the three main forms
of network access methods
Summarize the difference between guided media
and unguided media
Explain how a network operating system works
List the transmitting and receiving devices used in a
computer network
Describe the function of TCP/IP
Summarize the use of a VPN
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Introduction
 introduces the concept of computer networks
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Computer network (or network) - a group of
two or more computer systems linked together
using wires or radio waves over a
geographical area
Computer networks that do not use physical
wires are called wireless
 takes a detailed look at the key concepts
that are integrating computer networks and
data communications
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The Need for Networking
 A network provides two principle benefits:
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The ability to communicate
The ability to share
 Groupware - software that supports team
interactions and dynamics including
calendaring, scheduling, and
videoconferencing
is the most popular form of
network communication
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The Benefits of Computer Networking
 Store virtually any kind of information at, and
retrieve it from, a central location on the
network
 Combines the power and capabilities of
diverse equipment providing a collaborative
medium to combine the skills of different
people, regardless of physical location
 Enables people to share information and
ideas easily
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They can work more efficiently and
productively
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Networking Basics
 Networks are assembled according to certain
rules:
 Each cabling strand can only support a certain
amount of network traffic, etc
 Topology - the actual physical organization of
the computer devices including connections
 Bandwidth - indicates how much information can
be carried in a given time period over a wired or
wireless communications link
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Networking Basics (continued)
The network industry refers to nearly every type of
network as an “area network”
 Local Area Network (LAN) - connects network devices
over a relatively short distance
 Sometimes one building will contain a few small LANs,
and occasionally a LAN will span a group of nearby
buildings
 Wide Area Network (WAN) - is a geographically
dispersed telecommunications network
 Metropolitan Area Network (MAN) - interconnects users
in a geographic area or region larger than a local area
network, but smaller than a wide area network
 Example: A university may have a MAN that joins
together many of their local area networks situated
around its campus
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Networks – The Big Picture
 A network is made up of many physical
elements:
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Computers, printers, and other devices
 The manner in which all these items are
connected is referred to as the network
topology
 Network topologies are further subdivided
into two categories:
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Physical topologies
Logical topologies
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Physical Topologies
the actual physical organization of the computers on the
network and its connections
 Bus topology - all devices are connected to a central
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cable
Star topology - all devices are connected to a hub
Ring topology - all devices are connected to one
another in a closed loop
Tree topology - combines the characteristics of the
bus and star topologies
Wireless topology - all devices are connected by a
receiver/transmitter to a special network interface
card that transmits signals between a computer and a
server; all within an acceptable transmission range
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Physical Topologies
Network Access Methods (Protocols)
 Protocol - the predefined way that someone
(who wants to use a service) talks with or
utilizes that service
 The most popular LAN protocols include:
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Token Ring
Ethernet
Fiber Distributed Data Interface (FDDI)
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Token Ring
 Token ring network - a LAN in which all
computers are connected in a ring or star
topology and a token-passing schema is used in
order to prevent the collision of data between two
computers that want to send messages at the
same time
 Second most widely used protocol on local area
networks
 Data transfer rates of either 4 or 16 megabits per
second
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Ethernet
 Ethernet is the most widely installed LAN access
method originally developed by Xerox
 When it first began to be widely deployed in the
1980s, Ethernet supported a maximum data rate
of 10 megabits per second (Mbps)
 Fast Ethernet standards have extended
traditional Ethernet technology to 100 Mbps peak
 Gigabit Ethernet technology extends
performance up to 1000 Mbps
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Ethernet and Token Ring Network
Fiber Distributed Data Interface (FDDI)
 FDDI - a set of protocols for sending digital
data over fiber optic cable
 FDDI networks are token-passing networks
that supports data rates of up to 100
megabits per second
 FDDI networks are typically used as
backbones for wide area networks
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Fiber Distributed Data Interface
Networking Hardware
 To be sent from one location to another, a signal
must travel along a physical path
 The physical path that is used to carry a signal
between a signal transmitter and a signal
receiver is called the transmission medium
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Network transmission media - the various
types of media used to carry the signal
between computers
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Two types of transmission media: Guided and
Unguided
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Guided media
 Transmissions material manufactured so that signals
will be confined to a narrow path and will behave
predictably
 Three common types of guided media are: twistedpair wiring, coaxial cable, and fiber optic cable
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Twisted-Pair Wiring
a type of cable composed of four (or
more) copper wires twisted around
each other within a plastic sheath
 The wires are twisted to reduce outside
electrical interference
 The RJ-45 connectors on twisted-pair cables
resemble large telephone jacks
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Coaxial Cable
cable that can carry a wide range of
frequencies with low signal loss
 Consists of a metallic shield with a single wire
placed along the center of a shield and isolated
from the shield by an insulator
 Two different types
 Thinnet coaxial cable - similar to the cable
used by cable television companies
 Thicknet coaxial cable - similar to thinnet
except that it is larger in diameter
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Fiber Optic Cable
 Fiber optic (or "optical fiber") - the
technology associated with the transmission
of information as light impulses along a glass
or plastic wire or fiber
 Optical fiber cable can transmit data over
long distances with little loss in data integrity
 Optical fiber is not subject to interference
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Cable Summary
Unguided Media
 Unguided media - natural parts of the
Earth’s environment that can be used as
physical paths to carry electrical signals
 Examples include microwaves, infrared light
waves, and radio waves
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Transmitting and Receiving Devices
 Network adapters
 Modems
 Repeaters
 Wiring
concentrators, hubs,
and switches
 Bridges, routers,
 Microwave
transmitters
 Infrared and laser
transmitters
 Cellular transmitters
 Wireless LAN
transmitters
and gateways
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Network Adapters
 Network adapter - the hardware installed in
computers that enables them to communicate
on a network
 The most common form is designed to be
installed directly into a standard expansion
slot inside a PC
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Modems
 Modems - provide the means to transmit digital
computer data typically over ordinary telephone lines
 The transmitting modem converts the encoded
data signal to an audible signal and transmits it
 A modem connected at the other end of the line
receives the audible signal and converts it back
into a digital signal for the receiving computer
 Modems are commonly used for inexpensive
communications between a network and
geographically isolated computers
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Repeaters
used to increase the distance over which
a network signal can be propagated
 A signal travels through a transmission
medium, it encounters resistance and
gradually becomes weak and distorted
 The repeater receives the network signal and
retransmits it at the original transmission
strength
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Concentrators, Hubs, and Switches
 Concentrators, hubs, and switches -
provide a common physical connection point
for computing devices
 Most hubs and all wiring concentrators and
switches have built-in signal repeating
capability to perform signal repair and
retransmission
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Bridges, Routers, and Gateways
used to interconnect network segments
 Bridges
 Routers
Bridges and routers - generally used to
connect networks that use similar protocols
 Gateways
 used to connect networks that use dissimilar
protocols; examples includes TCP/IP and IPX
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Microwave Transmitters & Receivers
 commonly used to transmit network signals
over great distances
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Infrared and Laser Transmitters
 Infrared and laser transmitters - similar to
microwave systems: they use the atmosphere
and outer space as transmission media
 They require a line-of-sight transmission path
 Useful for signaling across short distances
where it is impractical to lay cable
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Cellular Transmitters
 Cellular transmitters - radio transmissions and
therefore have the advantage of being able to
penetrate solid objects
 A cellular base station at the center of each cell
contains:
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Low-power transmitters
Receivers
Antennas
Common control computer equipment
 Cellular devices are configured to operate at low
power to avoid interfering with other cellular devices
in the area
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Wireless LAN Transmitters
function like hubs and switches in a wired environment,
only they propagate signals through radio waves or
infrared light instead of wires
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The Network Operating System
an operating system that includes special
functions for connecting computers and
devices into a local area network
 Two categories:
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Client-server
Peer-to-peer
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Client-Server Networks
a versatile, message-based, and modular infrastructure
that is intended to improve usability, flexibility,
interoperability, and scalability as compared to
centralized, mainframe computing
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Thin Client-Server Networks
 Thin clients - similar to terminals connected
to mainframes, the server performs the bulk
of the processing, and the client presents the
interface
 Thin clients are usually devoid of floppy
drives, expansion slots, and hard disks;
consequently, the “box” or central processing
unit is much smaller than that of a
conventional PC
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Peer-to-Peer Networks
Enable networked
computers to
function as both
servers and
workstations
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Internet Technology
 The world’s largest computer network
 Two most influential technologies:
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Transmission Control Protocol/Internet
Protocol (TCP/IP) suite
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World Wide Web (WWW)
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TCP/IP
 TCP/IP - a group, or suite, of networking
protocols used to connect computers on the
Internet
 Two main protocols in the suite are:
 TCP provides transport functions, ensuring,
among other things, that the amount of data
received is the same as the amount
transmitted
 The IP part of TCP/IP provides the addressing
and routing mechanism
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The TCP/IP suite of applications
 File Transfer Protocol (FTP) - allows files to be
downloaded off or uploaded onto a network
 Simple Mail Transfer Protocol (SMTP) - TCP/IP’s
own messaging system for e-mail
 Telnet protocol - provides terminal emulation
 Hypertext Transfer Protocol (HTTP) - allows Web
browsers and servers to send and receive Web
pages
 Simple Network Management Protocol (SNTP) allows the management of networked nodes to be
managed from a single point
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The TCP/IP Protocol Suite
World Wide Web
 The World Wide Web is a client-server
environment
 Information is managed through Web sites on
computers called Web servers
 Accessing Web sites is done through the use of
client software (i.e., a browser) and the Internet’s
HTTP
 Computers and Web sites on the Internet are
linked through documents called Web pages
written in HTML
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Intranet vs. Extranet
 Intranet – an internalized portion of the Internet,
protected from outside access, that allows an
organization to provide access to information and
application software to only its employees
 Extranet - a private network that uses the
Internet protocol and the public
telecommunication system to securely share part
of a business's information or operations with
suppliers, vendors, partners, customers, or other
businesses
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Virtual Private Network (VPN)
 VPN - a private WAN that uses the Internet as a low-
cost WAN backbone to transport data between two or
more geographically separate sites
 Advantages that a VPN has over a dedicated-line
WAN:
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The cost of implementation
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No need to lay cable or lease dedicated lines between
the remote sites needing to connect
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Businesses can network remote offices into one large
WAN and provide access to the Internet
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Intranet, Extranet, and VPN Technologies