Network Topology

. What is topology?

• Topology refers to the way in which the various nodes or computers of a network are linked together.
• The topology of a network is the geometric representation.
• Two or more devices connect to a link; two or more links form a topology.

​

Network Topology

Types of Topologies

Bus Topology

• In this topology, there is a single communication line or cable that is shared by all the nodes in the network.
• All the devices in network are connected to this line by drop line and taps.
• Drop line:- is the connection between the devices and the cable.
• Tap:- is the splitter that cuts the main link.
• When one computer sends a signal up the cable, all the computers on the network receive the information but the message is accepted by only that computer whose address is specified in the address field; all other nodes reject the message.

​

Bus Topology

Advantages of Bus Topology

• It is easy to install, understand and the use for small networks.
• Cost is less as only one main cable is required.
• New node can be easily added by using a connector.
• Failure of one node does not affect the network functioning.
• The length of cable required is less than a star topology.

Disadvantages of Bus Topology

• If the main central line fails the entire network collapses.
• In this topology, only limited number of devices can be included.
• Sharing a single communication channel results in slower access time.
• Packet loss is high.
• Need terminators are required at both ends of the main cable.

Ring Topology

• In ring topology, the various nodes are connected in form of a ring or circle.
• In this data flows in a circle, from one station to another station.
• It has no beginning or end that needs to be terminated.
• There are two kind of ring topologies:
• Single Ring
• Dual Ring

Ring Topology

Advantages of Ring Topology

• There are no collisions.
• Data packets travel at greater speeds.
• Easy to install.
• Fault identification is easy.
• There is no master computer on controller.
• Every computer has equal chance to place the data and access the token.

Disadvantages of Ring Topology

• Unidirectional traffic.
• Break in a single ring can break entire network.
• A ring network requires more cable than a bus network.
• Adding or removing the node disturbs the network activity.
• Addition of new nodes in the network also increases communication delay.

Star Topology

• This topology has a central controller called Hub.
• Each computer in the network has a dedicated point to point link to the central controller.
• There is no direct link between these computers and the computers can communicate via central controller only.
• It means that if one computer A wants to send data to another computer B, computer A Sends the data to the controller & this controller then sends the data to computer B.

Star Topology

Advantages of Star topology

• Addition of new node does note increase communication delay.
• It is easier to add new node or modify any existing node without disturbing network.
• If any local computer or link fails, the entire system does not collapse.
• Fault identification and isolation is easier.
• Less Expensive.

Disadvantages of Star Topology

• If the central controller or hub fails, entire system collapses.
• Cabling cost is more as each node is connected individually to hub.
• If one link fails there is no alternative to connect it with rest of network.
• Hub requires more resources and regular maintenance because it’s the central system of star .
• Performance is predicated on the one concentrator i.e. hub�

Mesh Topology

• In this topology, each node is connected to every other node in the network.
• Mesh topology is used for long distance data communication.
• A mesh topology uses n(n-1)/2 physical links to connect n devices.
• Every node features a point-to-point connection to the opposite node.
• In case of failure of one path, the other one can be used.

Mesh Topology

Advantages of Mesh Topology

• It is robust as the failure of one node does not collapse the entire system.
• If one link fails, the entire system continues to work.
• A mesh doesn’t have a centralized authority.
• It provides high privacy and security.
• There is no traffic problem as there is a dedicated point to point links for every computer.
• Fault identification is straightforward.

​

Disadvantages of Mesh Topology

• Connecting each device to every other device in the network makes installation and reconfiguration difficult.
• It has high capable cost as n(n-1)/2 links are required to connect n nodes.
• Power requirement is higher as all the nodes will need to remain active all the time and share the load.
• Complex process.

​

Tree Topology

• Tree topology is the variation of star topology. As in a star, nodes in a tree are connected to central hub that controls the traffic of the network.
• Tree networks have hierarchical flow of data.
• The central hub in the tree is an active hub which contains repeater.
• The secondary hubs may be active or passive.
• In tree, data cam flow from top to bottom i.e. from central hub to secondary hub and then to devices or from bottom to top.

Tree Topology

Advantages to Tree Topology

• It allows more devices to be attached to a single central hub.
• It allows the network to isolate and prioritize communication from different computers.
• This topology is the combination of bus and star topology.
• Tree Topology is highly secure.
• It is used in WAN.
• Tree Topology is reliable.

​

Disadvantages of Tree Topology

• If the central hub fails, entire system fails.
• It has higher cabling cost in setting up a tree.
• This network is very difficult to configure as compared to the other network topologies.
• If the bulk of nodes is added to this network, then the maintenance will become complicated.
• Requires a large number of cables compared to star and ring topology.�

Hybrid Topology

• A hybrid topology is a topology is a topology that combines two or more different physical topologies in a single network.
• Three topologies Ring Star and Bus are combined to form a hybrid topology.
• The two most common hybrids found today are Star-Bus and Star-Ring topology.
• This mix of topologies is completed and consistent with the wants of the organization.

Hybrid Topology

Advantages of Hybrid Topology

• This topology is very flexible.
• The size of the network can be easily expanded by adding new devices.

​

Disadvantages of Hybrid Topology

• It is challenging to design the architecture of the Hybrid Network.
• Hubs used in this topology are very expensive.

​