Transcript Network Components Presentation

Networks
Network Components
Learning Objectives
Describe different media for transmitting
data and their carrying capabilities.
Explain the different purposes of network
components.
Transmission Media
(cables)
Presented in order of performance
(increasing expense, speed of communication, level of traffic that can be
managed, difficulty and usable length of installation and decreasing
susceptibility to interference)
http://members.tripod.com/barhoush_2/cabling.htm
http://fcit.usf.edu/network/chap4/chap4.htm
http://www.ecst.csuchico.edu/~sim/547/Old547/notes/NOTE4.htm
UTP & Shielded TP
Unshielded Twisted Pair (UTP)
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Two conductors, enclosed in a
plastic sheath, twisted together.
Shielded Twisted Pair
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Has a grounded screen around the
conductors to shield the cable from
extraneous electromagnetic
radiation.
Used in pre-existing telephone networks.
Changing current denotes different signals.
Coaxial cable
A central conductor enclosed in a plastic sheath
surrounded by a copper sheath which is
surrounded by a plastic coating.
Baseband coaxial:
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Single copper braid shield.
Broadband coaxial:
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Two shields
1 - aluminium & 1 - copper.
Copper screen
conductor
Central conductor
Plastic insulators
Used in pre-existing telephone networks.
Changing current denotes different signals.
Optical Fiber
- Used as backbones (fast route) for LANs
or in WANs
Contains many optical fibers:
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Glass or plastic fibers designed
to guide light along them.
Signals transmitted as light
pulses so travel at the speed of
light with the highest bandwidth
currently possible.
Separate fibres can be used for
separate signals.
Network Interface Cards (NIC)
Provides the hardware
interface (circuit board) to
connect a computer to a
network.
Some NIC cards work
with wired connections
while others are wireless.
http://en.wikipedia.org/wiki/Network_interface_controller
Wireless Communication
Radio signals:
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Satellite communications.
Microwave signals:
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Communication must be a straight line from
sender to receiver.
Wireless communication allows for mobile
communication.
Network Components
Repeater
Has only 2 ports and amplifies the signals between two
networks or segments of a bus network that are too far
apart.
Is not intelligent and simply amplifies all signals whether
they are intended for the other segment or not.
Operate at the physical layer of OSI.
Segment
Repeater
Hubs
Hub
Hubs
All signals received by a hub are
retransmitted down every other cable
connected to it enabling a physical star
network (but still theoretically a bus network as
collisions are possible).
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Multi-port repeaters.
Operate at the physical layer of OSI.
Bridges
Links only 2 LANs (which may or may not be
similar) by controlling access from one part
of the network to the other.
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Could be thought of as an intelligent repeater.
Segment
Bridge
Bridges
Has the ability to learn the layouts of the
networks.
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Initially, all data the bridge receives is buffered and
passed to both segments.
The bridge stores a table containing the addresses of
sending nodes and the segment from which the data
was sent.
Eventually, when all nodes have sent data, the bridge
will know on which segment each node is.
Now it can use the address information in each
packet to route data efficiently (either directing it back to
the segment it came from or on to the other segment).
Is software based as it uses software to make its
decisions.
Operate at the data layer of OSI.
Bridge Algorithm
1. Data arrives at the bridge and is
buffered.
2. Bridge checks destination address.
3. If destination is on same segment as
sender then
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discard the data
4. Else
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pass data to other segment.
Stations
Server
Switch
Stations
Server
Switch
Backbone
Switch
Stations
Switch
Server
Stations
Server
Switch
An ‘intelligent’ hub which looks at the destination
address of each packet it receives and delivers each
packet to the correct destination (i.e. connects nodes in a
circuit switching network).
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Like a bridge but can link many LANs.
It allows many terminals all to use the same
communications line (backbone – fast medium e.g. optical
fibre) between network segments at different times.
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If all stations want to access the main network, the switch has
no affect on the speed of this link and it may be necessary to
upgrade the link to the main network.
Operate at the data layer of OSI.
Switch
Only stores physical addresses and can
only deal with simple networks where
there is only one possible path for any
given packet.
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If this is not the case ‘routers’ must be used
(next).
Is hardware based as uses chips to
make its decisions.
Routers
LAN
Router
Public
network
Router
LAN
Routers
Connect different types of network
together.
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Stores logical IP addresses and can deal with
complex networks where there is more than
one possible path to a destination by
calculating the optimum route at the time.
i.e. Directs packets across a packet switched
network.
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Is software based as it uses its own operating
system to make its decisions.
Routers
Directs messages down different routes
according to their desired destinations.
Use network addresses and addresses of other
routers to create a route between two networks so
must keep tables of addresses.
 These tables are copied between routers using
routing information protocol (RIP).
 Often used to connects LANs & WANs e.g. connect a
LAN to the internet using one IP address.
Operates at all layers up to the transport layer of OSI.
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Routing Algorithm
1. Router receives a network level packet.
2. Network destination address is checked.
3. Packet is sent to the appropriate
network.
Gateway
A gateway is a network point/router that acts as an
entrance to another network.
On the Internet, a node/router or stopping point can be
either a gateway node or a host (end-point) node/router.
Both the computers of Internet users and the computers
that serve pages to users are host nodes.
The computers that control traffic within your company's
network or at your local Internet service provider (ISP)
are gateway nodes/routers.
In the network for an enterprise, a computer server
acting as a gateway node is often also acting as a proxy
server and a firewall server.
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http://en.wikipedia.org/wiki/Default_gateway
Modems
Necessary if communication link is
analogue
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e.g. To transmit and receive data on the
internet.
Hardware which converts digital signals to
analogue for transmission and vice versa
for receiving.
Firewall
Software (and possibly hardware) to control
unauthorised outside access to a private
network.
Plenary
Explain the part played in network
systems by:
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Switches
Routers
Bridges
Modems
Plenary
Switches
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A device that allows many terminals all to use the
same communications line at different times.
Routers
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Connects different types of network together.
Software at a node (on the network).
Which directs messages down different routes.
According to their desired destination.
Plenary
Bridges
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Links two LANs (which may or may not be similar).
Uses address information in packets.
Has the ability to learn the layouts of the networks.
Can control access from one part of the network to
the other.
Modems
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Necessary if communication link is analogue.
Converts digital signals to analogue for
transmission.