HNC COMPUTING - Network Concepts 1 Network Concepts Topologies Network Topologies

HNC COMPUTING - Network ConceptsHNC COMPUTING - Network Concepts 11

Network ConceptsNetwork ConceptsTopologiesTopologies

Network TopologiesNetwork Topologies


AimsAimsGain a knowledge about network Gain a knowledge about network topologies.topologies.

Discuss the advantages and Discuss the advantages and disadvantages of different network disadvantages of different network topologies.topologies.

Draw a network topology in VisioDraw a network topology in Visio


What is a network topologyWhat is a network topology

In computer terms, topology means the In computer terms, topology means the structure or layout of the communications structure or layout of the communications network.network.

Each workstation on a network is known Each workstation on a network is known as a node.as a node.


What is a network topologyWhat is a network topology

Types of NetworksTypes of Networks– ring, star, bus, meshring, star, bus, mesh– CombinedCombined


Ring NetworksRing Networks


Ring NetworksRing NetworksAn example of a Ring network is a token An example of a Ring network is a token ring networkring network

Each node connects to two other nodes Each node connects to two other nodes creating a circular effect.creating a circular effect.

Data travels from one node to another until Data travels from one node to another until the correct destination has been reached.the correct destination has been reached.


Ring NetworksRing NetworksA node handles every packet that is sent A node handles every packet that is sent through the network.through the network.

Access is achieved either by means of a token, Access is achieved either by means of a token, passed from one node to the other, or by pollingpassed from one node to the other, or by polling

The two main logical topologies which use this physical topology are Token ring and FDDI.



Some advantagesSome advantages– Orderly network because every device has to Orderly network because every device has to

access the token in order to transmit data.access the token in order to transmit data.

– Degrades gracefully. Network traffic gradually Degrades gracefully. Network traffic gradually slows down when busy opposed to Ethernet slows down when busy opposed to Ethernet which grounds to a halt.which grounds to a halt.



Some disadvantagesSome disadvantages– A failure in any cable or device breaks the A failure in any cable or device breaks the

loop and can take down the entire network.loop and can take down the entire network.

– Any movement of devices on the network can Any movement of devices on the network can cause it to fail.cause it to fail.


Star NetworksStar Networks



A star network consists of one central A star network consists of one central switch, hub or computer, which acts as a switch, hub or computer, which acts as a channel to transmit messages.channel to transmit messages.

Server dependent - often a mainframeServer dependent - often a mainframe



Some advantagesSome advantages– A Star Network Topology is very easy to manage A Star Network Topology is very easy to manage

because of its simplicity in functionality.because of its simplicity in functionality.

– The problems can be easily located logically in a Star The problems can be easily located logically in a Star Topology and therefore is easy to troubleshoot.Topology and therefore is easy to troubleshoot.

– The star topology reduces the chance of network failure The star topology reduces the chance of network failure by connecting all of the systems to a central nodeby connecting all of the systems to a central node

– It is easier to add additional nodesIt is easier to add additional nodes



Some disadvantagesSome disadvantages

– if the central hub fails, all computers if the central hub fails, all computers connected to that hub would be disconnected.connected to that hub would be disconnected.

– The performance and scalability of the The performance and scalability of the network depends on the capabilities of the network depends on the capabilities of the hub.hub.


Bus NetworksBus Networks



A A bus network topologybus network topology is a network is a network architecture in which a set of clients/nodes are architecture in which a set of clients/nodes are connected via a shared communications line, connected via a shared communications line, called a bus.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.



A media access method called CSMA (Carrier A media access method called CSMA (Carrier Sense Multiple Access) is used to handle the Sense Multiple Access) is used to handle the collision that occur when two signals placed on collision that occur when two signals placed on the wire at the same time. the wire at the same time.

The bus topology is passive. In other words, the The bus topology is passive. In other words, the computers on the bus simply 'listen' for a signal; computers on the bus simply 'listen' for a signal; they are not responsible for moving the signal they are not responsible for moving the signal along.along.



Some advantagesSome advantages– Easy to implement and extend Easy to implement and extend – Requires less cable length than a star Requires less cable length than a star

topologytopology – Cost effective as only a single cable is used.Cost effective as only a single cable is used.



Some disadvantagesSome disadvantages– If there is a problem with the cable, the entire If there is a problem with the cable, the entire

network goes down. network goes down. – Performance degrades as additional Performance degrades as additional

computers are added or on heavy traffic. computers are added or on heavy traffic. – It works best with limited number of nodes. It works best with limited number of nodes. – It is slower than the other topologies.It is slower than the other topologies.


Mesh NetworksMesh Networks



It allows for continuous connections and It allows for continuous connections and reconfiguration around broken or blocked paths reconfiguration around broken or blocked paths by “hopping” from node to node until the by “hopping” from node to node until the destination is reached.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.



Some advantagesSome 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.



Some disadvantagesSome disadvantages

– Setup time can be quite time consuming.Setup time can be quite time consuming.– ExpensiveExpensive

BTEC NAT - UNIT 27 - NETWORKINGBTEC NAT - UNIT 27 - NETWORKING

TREE TOPOLOGYTREE TOPOLOGY


TREE TOPOLOGYTREE TOPOLOGY

Advantages of a Tree Topology

Point-to-point wiring for individual segments. Supported by several hardware and software venders.Easily extendable – add new components

Disadvantages of a Tree Topology

Overall length of each segment is limited by the type of cabling used. If the backbone line breaks, the entire segment goes down. More difficult to configure and wire than other topologies.


COMBINED TOPOLOGIESCOMBINED TOPOLOGIES


ConclusionConclusion

Gained knowledge about network Gained knowledge about network topologies.topologies.

Discussed the advantages and Discussed the advantages and disadvantages of different network disadvantages of different network topologies.topologies.

Documents

HNC COMPUTING - Network Concepts 1 Network Concepts Topologies Network Topologies