This is the way an organisation distributes the data
across its network. It uses different types of networks to
communicate the information across it.
This is known as the Network Topology.
In the first section we will look at: Draw in jotter
Bus
Star
Ring
Mesh
Tree
Terminator
Terminator
Advantages:
•Easy to install because only needs one backbone.
•Computers easily connected or disconnected by drop
cable.
•Inexpensive and good for temporary networks needed
in a hurry.
•If one node fails the rest still work data still travels
along connection not through nodes.
Terminator
Terminator
Terminator
Terminator
Disadvantages:
•If backbone is damaged then the whole network is
down.
•Terminators are required at each end disadvantage is
that it takes time to attach them and they must be
installed correctly. (Stops the data going back down the
backbone causing interference).
•Difficult to find the damage in the backbone. Moving
terminator is one way of doing this but it is time
consuming.
•Not good to rely on a bus for a whole building (ok as
temporary or add on to existing network)
Connected to central hub or switch. All data passes
through central hub. Hub can also act as repeater
to boost the signal.
The hub reads the destination address and passes it
directly on to the correct IP address.
More cable is needed but it makes it easy to add or
remove nodes. (Just plug into cable outlet on wall).
Advantages:
Easy to install/remove a new node. No disruptions to
network as this is being done.
Easy to detect faults since it should only affect one
node.
Disadvantages:
Much more cabling needed for star network.
If central node fails all nodes are disabled.
More expensive because of cost of hub/switch as the
central node.
Nodes connected serially (one after another) in a circle.
Signal travels in clockwise direction.
Token needed to transmit data.
It travels around the ring, when a computer wants to send
message it grabs the token attaches the data and adds an
address to it.
This way only one message is travelling around the
network at one time.
No data collision.
When the message has been received the receiving node
sends back a message to the sending node the sender then
releases the token back onto the ring.
Each node boosts the signal as it travels around the ring.
Advantages:
Can increase the number of nodes without affecting the
performance of the system.
All nodes have equal access to the token and therefore
have equal communication rights.
Disadvantages:
Most expensive because they specialist hardware.
If one computer fails it may affect the rest of the nodes.
This is fully meshed
In a true mesh all computers are connected to every
other one. This is called fully meshed.
Fully meshed means if one node fails then the message
can still travel to its destination. Fully meshed mostly
used for backbone networks, i.e. the main connections
between networks.
Partially meshed means all the nodes are not connected
to every other one. Partially meshed means nodes may
only be connected to another two nodes.
Advantages:
If a connection is down then the data can easily travel
along another route.
Disadvantages:
Expensive, difficult to install because of so many
connections.
Difficult to manage because of complexity.
Difficult to detect errors because of number of
connections.
Answer Questions page 56 of notes
It is an interconnection of star
topologies. It allows the expansion of
existing networks.
Advantages
Easy to add new nodes, easy to add new segments.
Easy to install and wire a tree network. Connect the
central nodes and then the segments.
Each device on the network has its own connect to the
central node therefore no disruptions to network when
connecting or removing devices.
Easy to detect faults (only affects one node or segment).
Disadvantages
Each segment size depends on the type of cabling used.
If a connecting node fails the network fails.
More difficult to configure than the other networks.
Network that is restricted to one
room, building or site.
LAN cables are commonly called
UTP (Unshielded Twisted Pair).
The maximum length of a cable is
1000m. Although cables can be
linked together if a longer network
is needed.
LANs allow users to share
peripherals such as printers and
allow users to log on anywhere on
the network.
Network Strategy
Network Topology
Networks - LAN (Local Area Network) – in one
building.
•Device Sharing.
•Software Sharing.
•Data Sharing.
•Communication.
WAN (Wide Area Network) – over a city, country or the
world.
Uses telecommunication - cable, satellite fibre optic.
Distributed Networks – lots of networks attached together.
Example is the internet
Client-Server Network
Central server stores data files and login details.
Peer to Peer network
No central server, all stations equal.
Cheaper, data less secure.
Network Hardware
Network Adapter Card.
Built-in to the computer.
Allows the computer to send and receive data around the
network.
Structured Cabling.
Cables made from copper wire, co-axial cable,
fibre optic cable and twisted pairs.
Twisted pair Ethernet most Common.
Fibre Optic used to link over longer distances and
to carry a very high bandwidth.
Network
Adapter Card
Network Software
Network Operating System – 2 parts
Part 1 - The version that runs on the server is needed to control which
users and workstations can access the server, keep each user’s data
secure. Control the flow of information around the network. It is also
responsible for file and data sharing, communications between users
and hardware and peripheral sharing.
Part 2 - The version that runs on the personal computers to turn them
into network stations. Each workstation (computer) connected to the
network needs the Network Operating System installed before it can
connect successfully to the network facilities
Network Auditing and Monitoring Software.
This software keeps a track of network activity. It records user
activity and workstation activity. In a commercial organisation this
sort of auditing and monitoring can be used to detect fraud and
suspicious activity.
In the past decentralised because computing power
was limited and could only handle the workload of a
single department. A terminal attached to a
mainframe. The terminal did not have a lot of
computing power.
Then more powerful machines with more memory and
processing power + networks + communications =
centralised again.
There is still some decentralised computing - PCs and
laptops for example.
What is a distributed
database?
A distributed
database is a
database where
different parts of
the database or 2
or more files are
located at different
parts of the
network.
2008 Section 2
Q15. A monthly report is produced by several employees creating and
editing sections of the document and then sending those to an editor
over a Local Area Network.
(a) (i) Name a suitable topology for this Local Area Network and draw a
diagram of this topology.
2
2006 Section 1
Q9. What is a distributed database?
2