Topologies



What is topologies ???

Topology from the Greek is mean place and study,this  is a major area of mathematics concerned with properties that are preserved under continuous deformations of objects, such as deformations that involve stretching, but no tearing or gluing. It emerged through the development of concepts from geometry and set theory, such as space, dimension, and transformation.
Topology includes many subfields. The most basic and traditional division within topology is point-set topology, which establishes the foundational aspects of topology and investigates concepts inherent to topological spaces for basic examples include compactness and connectedness is algebraic topology, which generally tries to measure degrees of connectivity using algebraic constructs such as homotopy groups and homology; and geometric topology, which primarily studies manifolds and their embeddings (placements) in other manifolds. Some of the most active areas, such as low dimensional topology and graph theory, do not fit neatly in this division.

What is network topologies ???

Network topology is the layout pattern of interconnections of the various elements links and  nodes of a computer or biological network. Network topologies may be physical or logical. Physical topology refers to the physical design of a network including the devices, location and cable installation. Logical topology refers to how data is actually transferred in a network as opposed to its physical design. In general physical topology relates to a core network whereas logical topology relates to basic network.

A local area network (LAN) is one example of a network that exhibits both a physical topology and a logical topology. Any given node in the LAN has one or more links to one or more nodes in the network and the mapping of these links and nodes in a graph results in a geometric shape that may be used to describe the physical topology of the network. Likewise, the mapping of the data flow between the nodes in the network determines the logical topology of the network. The physical and logical topologies may or may not be identical in any particular network.

The type of network of topologies :

But I want to introduce just three network topologies such as ring topology, bus topology and star topology.

Ø  Ring Topology 

Ring topology is a ring network in the network topology in which each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node - a ring. Data travels from node to node, with each node along the way handling every packet.

Advantages

•   Data is quickly transferred without a ‘bottle neck’. (very fast, all data traffic is in the same direction.
• The transmission of data is relatively simple as packets travel in one direction only.
• Adding additional nodes has very little impact on bandwidth
• It prevents network collisions because of the media access method or architecture required.

Disadvantages

•  Data packets must pass through every computer between the sender and recipient therefore this makes it slower.
•  If any of the nodes fail then the ring is broken and data cannot be transmitted successfully.
• It is difficult to troubleshoot the ring.
• Because all stations are wired together, to add a station you must shut down the network temporarily.
• In order for all computers to communicate with each other, all computers must be turned on.

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Ø  Bus Network

A bus network topology is a network architecture in which a set of clients are connected via a shared communications line, called a bus. There are several common instances of the bus architecture, including one in the motherboard of most computers, and those in some versions of Ethernet networks.

 Advantages

•   Easy to implement and extend
• Well suited for temporary networks (quick setup)
• Initially less expensive than other topologies

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Disadvantages

•  Difficult to administer/troubleshoot.
• Limited cable length and number of stations.
• If there is a problem with the cable, the entire network goes down.
• Maintenance costs may be higher in the long run.
•  Performance degrades as additional computers are added or on heavy traffic.
• Low security (all computers on the bus can see all data transmissions).
• One virus in the network will affect all of them (but not as badly as a star or ring network).
• Proper termination is required.(loop must be in closed path).
• If one node fails, the whole network will shut down.
•  If many computers are attached, the amount of data flowing causes the network to slow down.

Ø  Star Network

Star network  are fairly easy to install and maintain. Nodes can be added to and removed from network with little or no disruption the nertwork.  

Advantages

•   Good performance
• easy to set up and to expand. Any non-centralised failure will have very little effect on the network, whereas on a ring network it would all fail with one fault

Disadvantages

•  Expensive to install
• Extra hardware required