Topologies:-is the arrangement of the nodes in a network.There are basic topologies used:
MESH topology is a way to route the data between the nodes.It provides a contiguous connection until the destination of the routed data is not arrived.Mesh network is seen any where in office where the computers are connected.The nodes are connected without any fashion.Mesh Networks are self healing networks as any breakdown occurs the data will adapt itself to go with any other path.It is a very reliable network.
Wireless mesh networks are developed by military applications.
The drawback of mesh is that it requires lot of wires for connecting the individual nodes separately.
STAR topology is the most common used topology.Here, there is a central HUB, SWITCH or COMPUTER which acts as a router for the nodes.Star topology reduces the chances of the errors as any failure occurred will be noticeable.All the nodes may communicate between each other, but via the central node only.
If any failure occurs it will not effect the performance of the other computers.
Advantage with star topology is that, it is simple to arrange, failure occurred will be easily noticeable, it gives a better performance as there is a central HUB for routing the data.Number of devices can be connected to a central node.
The only disadvantage is that, if the central HUB failed, then the whole network is gone.
RING topology has nodes connected to exactly two other nodes making a circle.The data is send clockwise.RING topology provides one way path, if one of the computer fails then whole network gone.It is hard to find the failed node as the network collapse(which will lead to checking of the individual computers).
Advantage is that it is better than the STAR topology in heavy work situation, it also does not require any central device as routing the data.
Disadvantage is that, when one computer fails whole network will go down, it is slow as the data will check all the destination computers for going to the right destination.
TREE This type of network topology, in which there is a central â€˜rootâ€™ node (the top level of the hierarchy) is connected to one or more other nodes that are one level lower in the hierarchy (i.e., the second level) with a point-to-point link between each of the second level nodes and the top level central â€˜rootâ€™ node, while each of the second level nodes that are connected to the top level central â€˜rootâ€™ node will also have one or more other nodes that are one level lower in the hierarchy (i.e., the third level) connected to it, also with a point-to-point link, the top level central â€˜rootâ€™ node being the only node that has no other node above it in the hierarchy â€“ the hierarchy of the tree is symmetrical, each node in the network having a specific fixed number, of nodes connected to it at the next lower level in the hierarchy, the number of, being referred to as the â€˜branching factorâ€™ of the hierarchical tree.
1.) A network that is based upon the physical hierarchical topology must have at least three levels in the hierarchy of the tree, since a network with a central â€˜rootâ€™ node and only one hierarchical level below it would exhibit the physical topology of a star.
2.) A network that is based upon the physical hierarchical topology and with a branching factor.
3.) The branching factor, is independent of the total number of nodes in the network and, therefore, if the nodes in the network require ports for connection to other nodes the total number of ports per node may be kept low even though the total number of nodes is large â€“ this makes the effect of the cost of adding ports to each node totally dependent upon the branching factor and may therefore be kept as low as required without any effect upon the total number of nodes that are possible.
4.) The total number of point-to-point links in a network that is based upon the physical hierarchical topology will be one less than the total number of nodes in the network.
5.) If the nodes in a network that is based upon the physical hierarchical topology are required to perform any processing upon the data that is transmitted between nodes in the network, the nodes that are at higher levels in the hierarchy will be required to perform more processing operations on behalf of other nodes than the nodes that are lower in the hierarchy.
BUS type of network topology in which all of the nodes of the network are connected to a common transmission medium which has exactly two endpoints (this is the â€˜busâ€™, which is also commonly referred to as the backbone of all data that is transmitted between nodes in the network is transmitted over this common transmission medium and is able to be received by all nodes in the network virtually simultaneously (disregarding propagation delays).
Note: The two endpoints of the common transmission medium are normally terminated with a device called a terminator that exhibits the characteristic impedance of the transmission medium and which dissipates or absorbs the energy that remains in the signal to prevent the signal from being reflected or propagated back onto the transmission medium in the opposite direction, which would cause interference with and degradation of the signals on the transmission medium.
Hybrid topology is a type of network topology that is composed of one or more interconnections of two or more networks that are based upon different physical topologies or a type of network topology that is composed of one or more interconnections of two or more networks that are based upon the same physical topology, but where the physical topology of the network resulting from such an interconnection does not meet the definition of the original physical topology of the interconnected networks (e.g the physical topology of a network that would result from an interconnection of two or more networks that are based upon the physical star topology might create a hybrid topology which resembles a mixture of the physical star and physical bus topologies or a mixture of the physical star and the physical tree topologies, depending upon how the individual networks are interconnected, while the physical topology of a network that would result from an interconnection of two or more networks that are based upon the physical distributed bus network retains the topology of a physical distributed bus network).