NETWORK TOPOLOGIES HNC COMPUTING - Network Concepts 1 Network Concepts Topologies

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

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

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

Ring Networks HNC COMPUTING - Network Concepts 5

Ring Networks HNC COMPUTING - Network Concepts 6 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.

Ring Networks HNC COMPUTING - Network Concepts 7 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.

Ring Networks HNC COMPUTING - Network Concepts 8 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.

Ring Networks HNC COMPUTING - Network Concepts 9 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.

Star Networks HNC COMPUTING - Network Concepts 10

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

Star Networks HNC COMPUTING - Network Concepts 12 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

Star Networks HNC COMPUTING - Network Concepts 13 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 Bus Networks

HNC COMPUTING - Network Concepts 15 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 16 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.

HNC COMPUTING - Network Concepts 17 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 18 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 19 Mesh Networks

HNC COMPUTING - Network Concepts 20 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 21 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 22 Mesh Networks Some disadvantages  Setup time can be quite time consuming.  Expensive

Tasks HNC COMPUTING - Network Concepts 23 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

Conclusion HNC COMPUTING - Network Concepts 24 Gained knowledge about network topologies. Discussed the advantages and disadvantages of different network topologies. Created a drawing in Visio to represent a network topology