Transcript network topologies

Network Concepts
Topologies
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NETWORK TOPOLOGIES
HNC COMPUTING - Network Concepts
Aims
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 Gain a knowledge about network topologies
 Discuss the advantages and disadvantages of
different network topologies
 Draw a network topology in Visio
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What is a network topology
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 In computer terms, topology means the structure or
layout of the communications network…logical
 Each workstation on a network is known as a node.
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What is a network topology
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 Types of Networks
 ring, star, bus, mesh
 Combined
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Ring Networks
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Ring Networks
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 An example of a Ring network is a token ring
network
 Each node connects to two other nodes creating a
circular effect.
 Data travels from one node to another until the
correct destination has been reached.
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Ring Networks
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 A node handles every packet that is sent through
the network.
 Access is achieved either by means of a token,
passed from one node to the other, or by polling
 The two main logical topologies which use this
physical topology are Token ring and FDDI.
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Ring Networks
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 Some advantages
 Orderly network because every device has to access the
token in order to transmit data.

Degrades gracefully. Network traffic gradually slows down
when busy opposed to Ethernet which grounds to a halt.
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Ring Networks
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 Some disadvantages
 A failure in any cable or device breaks the loop and can take
down the entire network.

Any movement of devices on the network can cause it to fail.
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Star Networks
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Star Networks
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 A star network consists of one central switch, hub
or computer, which acts as a channel to transmit
messages.
 Server dependent - often a mainframe
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Star Networks
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 Some advantages

A Star Network Topology is very easy to manage
because of its simplicity in functionality.
The problems can be easily located logically in a Star
Topology and therefore is easy to troubleshoot.
 The star topology reduces the chance of network failure
by connecting all of the systems to a central node


It is easier to add additional nodes
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Star Networks
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 Some disadvantages


if the central hub fails, all computers connected to that hub
would be disconnected.
The performance and scalability of the network depends on
the capabilities of the hub.
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Bus Networks
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Bus Networks
 A bus network topology is a network
architecture in which a set of clients/nodes are
connected via a shared communications line,
called a bus.
 A device wanting to communicate with another
device on the network sends a broadcast message
onto the wire that all other devices see, but only
the intended recipient actually accepts and
processes the message.
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Bus Networks
 A media access method called CSMA (Carrier
Sense Multiple Access) is used to handle the
collision that occur when two signals placed on
the wire at the same time.
 The bus topology is passive. In other words, the
computers on the bus simply 'listen' for a signal;
they are not responsible for moving the signal
along.
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Bus Networks
 Some advantages
 Easy to implement and extend
 Requires less cable length than a star topology
 Cost effective as only a single cable is used.
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Bus Networks
 Some disadvantages
 If there is a problem with the cable, the entire network goes
down.
 Performance degrades as additional computers are added or
on heavy traffic.
 It works best with limited number of nodes.
 It is slower than the other topologies.
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Mesh Networks
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Mesh Networks
 It allows for continuous connections and
reconfiguration around broken or blocked paths
by “hopping” from node to node until the
destination is reached.
 A netlike communications network in which
there are at least two pathways to each node. A
fully meshed network means that every node has
a direct connection to every other node.
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Mesh Networks
 Some advantages

Self-healing: the network can still operate even when a node
breaks down or a connection goes bad. As a result, a very
reliable network is formed.
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Mesh Networks
 Some disadvantages
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
Setup time can be quite time consuming.
Expensive
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Tasks
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 Write notes and/or store web links regarding token
ring networks.
 Find out about physical topologies and logical
topologies. – make notes.
 Research into different topologies, including
combined topologies.
 Select one topology and draw it in Visio
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Conclusion
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 Gained knowledge about network topologies.
 Discussed the advantages and disadvantages of
different network topologies.
 Created a drawing in Visio to represent a network
topology
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