The virtual shape or structure of a network is referred as topology. It is worth remembering that this virtual design does not correspond to the actual or the physical shape of the computer networks: you could arrange the home network in a circle but it does not replicate Ring Topology. The logical or/and physical connections between nodes could be mapped graphically for determining a network topology. Graph Theory is used for studying network topology: nodes’ distance, inter-connectivity, the rate of transmission and signal’s types of two networks might vary but their topologies could be identical.
The Technical Connotation of Topology
The pattern or layout of interconnections of different elements or nodes of a computer network is a network topology that might be logical or physical. As opposed to physical design, the transfer of data in a network is referred in Logical Topology (the basic network) where the Physical Topology (the core network) accounts the physical structure of a network that carries devices, cable installations and locations. LAN (local area network) is an example of network that keeps both logical and physical topologies.
What are the Basic Types of Topology?
There are seven basic types of network topologies in the study of network topology: Point-to-point topology, bus (point-to-multipoint) topology, ring topology, star topology, hybrid topology, mesh topology and tree topology. The interconnections between computers whether logical or physical are the foundation of this classification.
Logical topology is the way a computer in a given network transmits information, not the way it looks or connected, along with the varying speeds of cables used from one network to another. On the other hand the physical topology is affected by a number of factors: troubleshooting technique, installation cost, office layout and cables’ types. The physical topology is figured out on the basis of a network’s capability to access media and devices, the fault tolerance desired and the cost of telecommunications circuits.
The classification of networks by the virtue of their physical span is as follows: Local Area Networks (LAN), Wide Area Internetworks (WAN) and Metropolitan Area Networks or campus or building internetworks.
How Is the Physical Topology Classified?
Point-to-Point Network Topology
It is the basic model of typical telephony. The simplest topology is a permanent connection between two points. The value of a demanding point-to-point network is proportionate to the number of subscribers’ potential pairs. It is possible to establish a permanent circuit within many switched telecommunication systems: the telephone present in a lobby would always connect to the same port, no matter what number is being dialed. A switch connection would save the cost between two points where the resources could be released when no longer required.
Bus Network Topology
LANs that make use of bus topology connects each node to a single cable. Some connector connects each computer or server to the bus cable. For avoiding the bouncing of signal a terminator is used at each end of the bus cable. The source transmits a signal that travels in both directions and passes all machines unless it finds the system with IP address, the intended recipient. The data is ignored in case the address is unmatched. The installation of one cable makes bus topology an inexpensive solution as compared to other topologies; however the maintenance cost is high. If the cable is broken all systems would collapse.
Linear Bus: If all network nodes are connected to a combine transmission medium that has two endpoints the Bus is Linear. The data transmitted between these nodes is transmitted over the combine medium and received by all nodes simultaneously.
Distributed Bus: If all network nodes are connected to a combine transmission medium that has more than two endpoints created by branching the main section of the transmitting medium.
- Star Network Topology
The topology when each network host is connected to a central hub in LAN is called Star. Each node is connected to the hub with a point-to-point connection. All traffic passes through the hub that serves as a repeater or signal booster. The easiest Star topology to install is hailed for its simplicity to add more nodes but criticized for making hub the single point of failure. The network could be BMA (broadcast multi-access) or NBMA (non-broadcast multi-access) depending on whether the signal is automatically propagated at the hub to all spokes or individually spokes with those who are addressed.
- Extended Star: A network that keeps one or more than one repeaters between the central node or hub and the peripheral or the spoke node, supported by the transmitter power of the hub and beyond that supported by the standard of the physical layer of the network.
- Distributed Star: The topology is based on the linear connectivity that is Daisy Chained with no top or centre level connection points.
Ring Network Topology
Such physical setting sets up nodes in a circular manner where the data could travel in one direction where each device on the right serves as a repeater to strengthen the signal as it moves ahead.
Mesh Network Topology
The exponent of the number of subscribers is proportionate to the value of the fully meshed networks.
- Fully Connected: For practical networks such topology is too complex and costly but highly recommended for small number of interconnected nodes.
- Partially Connected: This set up involves the connection of some nodes to more than one nodes in the network via point-to-point link. In such connection it is possible to take advantage of the redundancy without any complexity or expense of establishing a connection between each node.
Tree Network Topology
the top level of the hierarchy, the central root node is connected to some nodes that are a level low in the hierarchy by a point-to-point link where the second level nodes that are already connected to central root would be connected to the nodes in the third level by a point-to-point link. The central root would be the only node having no higher node in the hierarchy. The tree hierarchy is symmetrical. The BRANCHING FACTOR is the fixed number of nodes connected to the next level in the hierarchy. Such network must have at least three levels. Physical Linear Tree Topology would be of a network whose Branching Factor is one.
Knowledge of networking topologies is of core importance of computer networking design. Computer networks can only be developed using the knowledge about these topoliges and decide to which topology design is best suited according to the requirement.