Network topology means the physical layout of a LAN. It includes geometrical arrangement of computer resources, remote devices and communication facilities. Each device or computer in the network is called a node. Following topologies are most common for local area networking
Star topology – In this topology host computer is the server of the network. This host can be mainframe or a smaller computer. The printer and the database are the parts of this host computer. It is located in center of the network and all other nodes are connected to it. All the messages are routed through the host. In case of its failure, the whole network fails.
Ring topology – In this arrangement, all the nodes are connected in a circle. The network has no host computer. The message travels along the ring connectivity in one direction or both the directions and reaches a particular computer to which it is addressed. In case of failure of ring connection, the entire network starting from the faulty device to the end of chain fails.
Bus topology – Bus topology does not consist of a host computer instead each node forms an independent part of the network. The messages are transmitted from one node to another without travelling through any other unaddressed node. In this case, the network does not fail even if more or more computers fail.
Tree topology – It consists of several computers linked in a hierarchical manner. The messages are transmitted from the main computer to the terminal computers, from where it is transmitted onward to other nodes. In this case if main computer fails, the entire network is rendered inoperative. However, it is easier to isolate a defective node or the entire branch from the main computer.
Mesh topology – In this topology, each workstation has to send message frequently to all other workstations. It has a few main sites and a large number of remote offices or sites. This topology is very infrastructure-extensive and needs periodic maintenance for all the multiple connection points, however it's the fastest operating topology.
The physical and logical arrangement of computer network devices is termed as a topology. The network devices called nodes are connected through transmission lines. The layout of such connected devices is called as a network topology. Network topologies can be further classified into Bus, Ring, Star, Mesh, Tree and Hybrid topologies.
Bus Topology:
The bus topology is used to carry the message, that needs to be transmitted, through a single cable. A single cable is used to connect the entire campus or building where the entire nodes are connected through two endpoints called backbones through transmission lines and switching elements.
The nodes will check the message for its destination address. If the address matches for a particular node the transmitted messages will be delivered by that particular host. Otherwise, the messages will be forwarded till it reaches the intended recipient. Benefits are reliable, least expensive and scalable. Demerits are when a node becomes corrupted or failure the whole network infrastructure may collapse and the messages may not be delivered.
Ring Topology:
In a Ring topology, every node is connected as a closed loop where it communicates with its adjacent neighbors called as previous and the next. The transmission of data is done through tokens in a unidirectional manner.
Star Topology:
In a Star topology, each and every node is connected directly to a central network. The data is passed through a hub, switch or concentrator until it reaches the particular destination. The advantage here is an easy installation, easy fault detection, and removal.
Mesh Topology:
In a Mesh topology, each and every network is interconnected with each other which involves the concept of routes. The advantage here is a failure in one node cannot affect the other nodes since the nodes are interconnected with each other. Disadvantage is cabling costs are high
Tree Topology:
In a tree topology, the nodes are connected in a hierarchical manner where the top node is called as a root or parent node and the other nodes are called as child nodes. The last level is called as leaf nodes. The branching of network terminals follows a hierarchical tree-like structure.
Hybrid Topology:
The combination of two or more topologies is termed as a hybrid topology where the users can design and combine their own topologies as per requirement.
Types of Network Topology: Network Topology is the schematic description of a network arrangement, connecting various nodes(sender and receiver) through lines of connection.
Bus Topology: Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear Bus topology.
Ring Topology: It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbors for each device.
STAR Topology: In this type of topology, all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.
Mesh Topology: It is a point-to-point connection to other nodes or devices. All the network nodes are connected to each other. Mesh has n(n-1)/2 physical channels to link n devices.
There are two techniques to transmit data over the Mesh topology, they are :
- Routing
- Flooding
TREE Topology: It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.
Hybrid Topology: It is two different types of topologies which is a mixture of two or more topologies. For example, if in an office in one department ring topology is used and in another star, topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).
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