Transcript Vishesh Network Components - IT Knowledge Base

Vishesh Kumar
 Routers
 Repeaters
 Bridges
 Hub
 Switches
 Gateways
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 Fillers
 Servers
 Modems
 Network
 Cables
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Cards
You will all have come across
the term 'Computer
Networks' many times. The
chances are you know all
about LANs and WANs,
network topologies, Intranets
and Internet.
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A Router is a device that
transfers data from one
network to another in an
intelligent way. It has the task
of forwarding data packets to
their destination by the most
efficient route.
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• Reads the data packet's destination
address
• Looks up all the paths it has available
to get to that address.
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• Checks on how busy each path is at the
moment
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• Sends the packet along the least congested
(fastest) path.
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• ill signals fade as they travel from one place to another.
• Each type of network cable has a maximum useable
length. If you go beyond that length, the signal will be
too weak to be useful.
• Of course, computers on a real network can easily be
more than 200 meters apart. Therefore the network
cable is split up into segments. Each segment is less
than the maximum length allowed. Joining the segments
together is a device known as a 'Repeater'.
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• A Bridge does just what you would expect it to do - it
joins two networks together so as far as data packets
are concerned it looks like one large network
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There are many network topologies available:
Star - uses a hub
Tree - uses a hub
Bus - does not use a hub
Ring - does not use a hub
To allow the Star and Tree network topologies to work
properly, each computer must be able to send data
packets to any other computer on the network.
• The network 'Hub' allows computers to share data
packets within a network.
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• Each computer will be connected to a single 'port' on
the hub. So if you purchase an '8 port hub', you will be
able to connect up to eight computers together.
• You can also 'daisy chain' hubs to allow even more
computers to join the network.
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• A network cable can only have one data packet in it at
any instant.
• So if two or more computers want to place a data packet
on to the network at exactly the same time, then a 'data
collision' will take place.
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• A gateway converts the data passing between dissimilar
networks so that each side can communicate with each
other. i.e. converts data into the correct network
protocol.
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• Just like Gateways, a Filter can be a mix of hardware
and software components.
• A filter can also prevent data packets from leaving the
company network. For example, a rule could be set up
that only allows an authorized server within the network
to send data outside the local network.
• A filter is an essential component of a 'Firewall'.
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• In some small networks, every machine is equally likely
to have a resource that another machine needs to use.
• For example a small home network may be set up like
this:
• There are files stored on each computer. One machine
is linked to the scanner, whilst another is linked to a
printer. The game machine is linked to the internet,
which all three machines can use.
• This is fine for small networks as the number of
requests to use a resource is not going to be too high.
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• A server is any machine that provides a service for other
users on the network.
Common services include:
• Email server
• Internet Proxy server
• Intranet server.
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• Some trivia: 'Modem' is a made-up word.
• Originally engineers called it the 'MODulation DEModulation' box. But it was such a mouthful that
naturally they ended up calling it the MODEM.
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• Standard modems come in two forms. An external box
that links to your computer either through a serial or
USB port, or an internal modem that is plugged directly
to the motherboard inside the computer.
Wi-Fi modems
• In addition to telephone modems, radio has now
become very popular as a means of connecting to the
internet. The device that allows you to do this is called
the Wi-Fi modem
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• Network cards are required in every machine connected
to the network. They allow the signal from the network
to be transmitted to the machine – this could be via a
fixed cable, infra red or radio waves.
A network card that uses a standard cable network socket.
A Wi-Fi network card with an external aerial for the signal.
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How do you transfer data from one point to another on a
network?
This has to be done by some physical effect.
There are three main methods of transferring data:
• Electrical
• Radio or Microwave
• Infrared
• Electrical:
• A multi-wired cable with a socket at each end is used to
connect the various devices together e.g. computer to
hub, hub to switch or switch to router etc.
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Radio or Microwave
Microwaves are just a small part of the radio spectrum,
but because they are so widely used, they tend to be
called by their own name.
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Infra-Red
This is a very familiar method of transferring data if you
are at all aware of your remote control ! The television
remote control makes use of an infra-red link.
PDA and personal organisers often make use of an infrared link to synchronise calendars and 'to-do' lists.
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MCA -5th Sem.