Ans. Network Topology- The term Computer network topology defines the geographic arrangement of computer networking devices. It describes the actual layout of the Computer Network hardware. Given the location of workstations and peripherals, the goal of topology is to find the most economical and efficient way to connect all the users to the computer network resources while providing adequate capacity to handle user demands, maintain system reliability and minimize delay. The selection of a Network Topology for a network can not be done in isolation as it affects the choice of media and the access method used. Because it determines the strategy used in wiring a building for a network and deserves some careful study. Basic Network Topology
The three simple LAN Network Topology that are combined to form any practical topology are known as basic LAN Network Topology. They are, Bus Topology, Ring Topology and Star Topology. 1. Bus Network Topology.
The physical Bus Network Topology is the simplest and most widely used of the network designs. It consists of one continuous length of cable (trunk) and a terminating resistor (terminator) at each end. Data communication message travels along the bus in both directions until it is picked up by a workstation or server NIC. If the message is missed or not recognized, it reaches the end of the cabling and dissipates at the terminator. Bus Network Topology requires a multipoint connection. All nodes on the bus topology have equal access to the trunk. This is accomplished using short drop cables or direct T-connectors. The number of devices and the length of the trunk can be easily expanded. Advantages of bus Network Topology
The advantages of physical bus topology are:
a. It uses established standards and it is relatively easy to install. b. It requires less media than other topologies.
Disadvantages of Bus Network Topology
The disadvantages of bus Network Topology are:
a. The bus networks are difficult to reconfigure, especially when the acceptable number of connections or maximum distances have been reached. b. They are also difficult to troubleshoot because everything happens on a single media segment. This can have dangerous consequences because any break in the cabling brings the network to its knee. 2. Ring Network Topology
The physical ring Network Topology is a circular loop of point-to-point links. Each device connects directly to the ring or indirectly through and interface device or drop cable. Message travel around the ring from node to node in a very organized manner. Each workstation checks the message for a matching destination address. If the address doesn't match the node simply regenerates the message and sends it on its way. If the address matches, the node accepts the message and sends a reply to the originating sender. Advantages of Ring Network Topology.
The advantages of Ring Network Topology are:
a. They are very easy to troubleshoot because each device incorporates a repeater. b. A special internal feature called beaconing allows troubled workstations to identify themselves quickly. Disadvantages of Ring Network Topology
The disadvantages of ring topologies are:
a. It is considerably difficult to install and reconfigure ring Network Topology b. Media failure on unidirectional or single loop causes complete network failure. 3. Star Network Topology
The physical star Network Topology uses a central controlling hub with dedicated legs pointing in all directions – like points of a star. Each network device has a dedicated point-to-point link to the central hub. This strategy prevents troublesome collisions and keeps the lines of communications open and free of traffic. This Network Topology, obviously, require a great deal of cabling. This design provides an excellent platform for reconfiguration and trouble-shooting. Changes to the...