1. Network Concepts Topologies
Network Topologies
HNC COMPUTING - Network Concepts

2. HNC COMPUTING - Network Concepts
Aims
Gain a knowledge about network topologies.
Discuss the advantages and disadvantages of different network topologies.
Draw a network topology in Visio
HNC COMPUTING - Network Concepts

3. What is a network topology
In computer terms, topology means the structure or layout of the communications network.
Each workstation on a network is known as a node.
HNC COMPUTING - Network Concepts

4. What is a network topology
Types of Networks
ring, star, bus, mesh
Combined
HNC COMPUTING - Network Concepts

5. HNC COMPUTING - Network Concepts
Ring Networks
HNC COMPUTING - Network Concepts

6. HNC COMPUTING - Network Concepts
Ring Networks
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.
HNC COMPUTING - Network Concepts

7. HNC COMPUTING - Network Concepts
Ring Networks
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.
Multistation Access Unit, a hub to which nodes connect on a Token Ring network.
FDDI (Fiber Distributed Data Interface) technology is network access technology over fibre optic type lines. It is in fact a pair of rings (one is called "primary", the other which makes it possible to capture errors from the first, is called "secondary") FDDI is a token ring network with detection and correction of errors (it is here where the secondary ring becomes important).
HNC COMPUTING - Network Concepts

8. HNC COMPUTING - Network Concepts
Ring Networks
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.
HNC COMPUTING - Network Concepts

9. HNC COMPUTING - Network Concepts
Ring Networks
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.
HNC COMPUTING - Network Concepts

10. HNC COMPUTING - Network Concepts
Star Networks
HNC COMPUTING - Network Concepts

11. HNC COMPUTING - Network Concepts
Star Networks
A star network consists of one central switch, hub or computer, which acts as a channel to transmit messages.
Server dependent - often a mainframe
HNC COMPUTING - Network Concepts

12. HNC COMPUTING - Network Concepts
Star Networks
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
HNC COMPUTING - Network Concepts

13. HNC COMPUTING - Network Concepts
Star Networks
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.
HNC COMPUTING - Network Concepts

14. HNC COMPUTING - Network Concepts
Bus Networks
HNC COMPUTING - Network Concepts 14

15. HNC COMPUTING - Network Concepts
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.
HNC COMPUTING - Network Concepts 15

16. HNC COMPUTING - Network Concepts
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.
CSMA
Carrier Sense Multiple Access (CSMA) is a probabilistic Media Access Control (MAC) protocol in which a node verifies the absence of other traffic before transmitting on a shared physical medium, such as an electrical bus, or a band of electromagnetic spectrum.
"Carrier Sense" describes the fact that a transmitter listens for a carrier wave before trying to send. That is, it tries to detect the presence of an encoded signal from another station before attempting to transmit. If a carrier is sensed, the station waits for the transmission in progress to finish before initiating its own transmission.
"Multiple Access" describes the fact that multiple stations send and receive on the medium. Transmissions by one node are generally received by all other stations using the medium.
HNC COMPUTING - Network Concepts 16

17. HNC COMPUTING - Network Concepts
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.
HNC COMPUTING - Network Concepts 17

18. HNC COMPUTING - Network Concepts
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.
HNC COMPUTING - Network Concepts 18

19. HNC COMPUTING - Network Concepts
Mesh Networks
HNC COMPUTING - Network Concepts 19

20. HNC COMPUTING - Network Concepts
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.
HNC COMPUTING - Network Concepts 20

21. HNC COMPUTING - Network Concepts
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.
HNC COMPUTING - Network Concepts 21

22. HNC COMPUTING - Network Concepts
Mesh Networks
Some disadvantages
Setup time can be quite time consuming.
Expensive
HNC COMPUTING - Network Concepts 22

23. BTEC NAT - UNIT 27 - NETWORKING
TREE TOPOLOGY
BTEC NAT - UNIT 27 - NETWORKING

24. BTEC NAT - UNIT 27 - NETWORKING
TREE 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.
BTEC NAT - UNIT 27 - NETWORKING

25. BTEC NAT - UNIT 27 - NETWORKING
COMBINED TOPOLOGIES
BTEC NAT - UNIT 27 - NETWORKING

26. HNC COMPUTING - Network Concepts
Conclusion
Gained knowledge about network topologies.
Discussed the advantages and disadvantages of different network topologies.
HNC COMPUTING - Network Concepts