Transcript Network Hardware and Software

Network Hardware
and Software
What is a network?
A network consists
of two or more
computers that are
linked in order to:
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share resources
(such as printers and
CD-ROMs),
exchange files, or
allow electronic
communications
How are they linked?
Computers on a
network may be
linked through:
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cables,
telephone lines,
radio waves,
satellites or
wireless
technologies
The two basic types of
networks include:
Local Area Networks
(LAN)
Wide Area Networks
(WAN)
LAN
WAN
Local area networks
LANs are confined to a relatively small
area such as a school or a building
LANs usually have one computer
designated as the file server
Other computers are connected to the
network by cables connecting network
interface cards in each computer
Wide Area Networks
WANs connect
larger areas, such
as whole states, or
even the world.
Transoceanic cables
and satellites are
used to connect
WANs
Protocol
A protocol is a set of
rules that governs the
communications
between computers
on a network
These rules include
guidelines that
regulate the method of
access, types of
cabling and speed of
data transfer
PROTOCOL =
SET OF RULES
ABOUT
COMMUNICATIONS
BETWEEN
NETWORKS!
The most common
protocols are:
Ethernet
Local Talk
Token Ring
FDDI
ATM
Protocol = a formal
description of a set of
rules and conventions
that govern how
devices on a network
exchange information
Did you ever wonder what HTTP in web addresses
was about? It stands for HyperText Transfer Protocol
Ethernet
Most widely used
Uses an access
method called
CSMA/CD (Carrier
Sense Multiple
Access/Collision
Detection
What does that mean?
Each computer in the
network ‘listens’ to the
cable before sending
anything through the
network. If the network
is clear, the computer
will transmit.
If another computer is
already transmitting on
the cable, the computer
will wait and try again
when the line is clear
A bit like waiting for
your younger sister to
get off the telephone
perhaps?
Ethernet (continued)
Sometimes, two computers
attempt to transmit at the
same instant. When this
happens, a collision occurs.
Each computer then backs off
and waits a random amount of
time before attempting to
retransmit.It is normal to have
collisions using this method,
but the delays caused by
collisions and transmissions is
small, and does not effect
speed of transmission on the
network
CSMA/CD =Carrier
Sense Multiple
Access /Collision
Detection
Ethernet (continued)
Ethernet protocol
allows for data to be
transmitted over
twisted pair, coaxial
or fiber optic cable
at a speed of 10
Mbps
(more on that later)
Fast Ethernet
To allow for faster
transmission, the
Ethernet protocol has
developed a new
standard that
supports 100 Mbps
Fast Ethernet
requires the use of
more expensive
equipment and
network cards
Gigabit Ethernet
The Ethernet
protocol has also
developed a new
standard that allows
transmission of 1
Gbps (gigabit per
second)
One gigabit per
second = one
thousand
megabits per
second
Local Talk
Local Talk is a network
protocol that was
developed by Apple for
Macintosh computers
Local Talk uses the
CSMA/CA method
(Carrier Sense Multiple
Access with Collision
Avoidance) which works
in a similar way to
CSMA/CD
It is a lot slower than
Ethernet (only 230 Kbps)
Token Ring
Token ring
protocol involves
‘token-passing’.
It is not as
popular as
Ethernet protocol
A single electronic ‘token’
moves around the ring from
one computer to the next. If a
computer wishes to transit
and receives an empty token,
it attaches data to the token
which then proceeds around
the ring until it comes to the
computer the data is meant
for.
FDDI
Stands for Fiber
Distributed Data
Interface
Is used mainly to
connect two or more
LANs, often over
large distances
Can operate over
fiber optic cable at
100 Mbps
ATM
Stands for Asynchronous
Transfer Mode
Transmit data at a speed
of 155 Mbps and higher
Works by transmitting all
data in small packets of
fixed size (other protocols
transfer variable size
packets)
Like FDDI , is most often
used to connect two or
more LANs
Where does TCP/IP fit
into all this???
TCP/IP is the protocol that is used for the
transmission of information over the Internet
IP (Internet Protocol) - the main delivery system
for information over the Internet
TCP (Transport Control Protocol) - used to
break apart and rebuild information that travels
over the Internet
Network Hardware
Network hardware
includes:
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Computers
Peripherals
Interface cards and
Other equipment
needed to perform
data processing and
communications
within the network
File servers
A very fast computer
with a large amount
of RAM and storage
space along with a
fast network
interface card
The network
operating system
software resides on
this computer
Workstations
All computers
connected to the file
server on a network
are called
workstations
Network interface cards
The network interface card
(NIC) provides the physical
connection between the
network and the computer
workstation.
Most NICs are internal with
the card fitting into an
expansion slot in the
computer.
Three common network
interface connections are
Ethernet cards, Local Talk
connectors and Token
Ring cards
Ethernet cards
The most common
Network Interface
Cards are Ethernet
cards
They contain
connections for
either coaxial or
twisted pair cables,
or both
Co-axial
cable
Twisted
pair cable
Concentrators / Hubs
A concentrator is a
device that provides
a central connection
point for cables from
workstations,
servers and
peripherals
Hubs are multi-slot
concentrators
Switches
While hubs provide an
easy way to scale up and
shorten the distance that
the packets must travel to
get from one node to
another, they do not break
up the actual network into
discrete segments. That is
where switches come in.
Switches (continued)
A vital difference between a hub and a switch is that all
the nodes connected to a hub share the bandwidth
among themselves, while a device connected to a switch
port has the full bandwidth all to itself.
Think of a switch as a ‘clever’ hub
Repeaters
A signal loses strength as it passes
along a cable, so it is often necessary
to boost the signal with a device called
a repeater
A repeater might be a separate device,
or might be part of a concentrator
Bridges
A bridge is a device that allows you
to segment a large network into two
smaller, more efficient networks
Routers
A router translates
information from one
network to another
The router directs traffic to
prevent “head-on”
collisions
If you have a LAN that you
want to connect to the
Internet, you will need a
router to serve as the
translator between
information on your LAN
and the Internet
Routers (continued)
Cabling
Network cabling is the
medium through which
information usually
moves from one
network device to
another
There are several
different types of cable
commonly used in
LANS
Some networks use a
variety of cable types
within the one network
Unshielded Twisted Pair
(UTP) Cable
Twisted pair cables
come in two varieties:
shielded and
unshielded.
Unshielded (UTP) is
the most popular
Shielded twisted pair is
used only in
environments where
there may be electrical
interference
UTP (continued)
UTP has four pairs of wires inside the jacket
Each pair is twisted with a different number of
twists per inch to help eliminate interference
from adjacent pairs
UTP Connector
The standard
connector for UTP
cabling is an RJ-45.
It looks like a
telephone style
connection
Coaxial cable
Coaxial cable has a single copper conductor at its
centre with a plastic layer between the centre
conductor and the braided metal shield
Although coaxial cabling is difficult to install, it is
highly resistant to signal interference
Coaxial cable connectors
The most common type of connector
used with coaxial cables is the BNC
connector
Fiber Optic Cable
Fiber optic cabling consists of a center glass
core surrounded by several layers of protective
materials
It transmits light rather than electronic signals
It is the standard for connecting networks
between buildings, due to its immunity to the
effects of moisture and light
Fiber Optic (continued)
Fiber optic cable has the ability to transmit
signals over much longer distances than
coaxial or twisted pair
It can also carry information at vastly greater
speeds
Fiber optic cable is more difficult to install than
other cabling
Wireless LANS
Wireless networks use high frequency radio
signals to communicate between the
workstations and the fileserver or hubs.
Disadvantages of wireless networks are:
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they are expensive (relatively),
provide poor security,
are susceptible to interference and
are slower than cabled networks
Network Operating
Software
Network operating
systems co-ordinate the
activities of multiple
computers across a
network
The two major types of
network OS are:
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Peer-to-peer
Client/server
Peer to peer network OS
In peer to peer network OS,
there is no file server or central
management source; all
computers are considered equal
Peer to peer networks are
design primarily for small to
medium LANS
AppleShare and Windows for
Workgroups are examples of
programs that can function as
peer to peer
Client/Server network OS
Client/server network OS
centralise functions and
applications in one or more
dedicated file servers.
The file server provides
access to resources and
provides security
Novelle Netware and
Windows NT Server are
examples of client/server
network operating systems
Topology
The physical topology of a network refers to
the configuration of cables, computers and
other peripherals.
The main types of network topologies are:
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Linear Bus
Star
Ring
Tree or Hybrid
Linear Bus
A linear bus topology consists of a main run of
cable with a terminator at each end. All servers
workstations and peripherals are connected to
the linear cable
Star
A star network is
designed with each
node (file server,
workstation,
peripheral)
connected directly to
a central network
hub or server
Ring
A ring network is
one where all
workstations and
other devices are
connected in a
continuous loop.
There is no central
server
Tree or hybrid
A tree or hybrid
topology combines
characteristics of
linear bus and star
and/or ring
topologies.
It consists of groups
of star-configured
workstations
connected to a
linear bus backbone
cable