bus TOPOLOGY

·          **TOPOLOGY:-

·          Topology refers to the way in which the computers are connected in a network.

·          Topology can be physical or logical.

·          The choice of topology depends on:-

·          Type and no. of equipment being used

·          Rate of data transfers

·          Required response time

·          Cost

·          Different type of topology is:-

·          Bus

·          Ring

·          Star

·          Tree

·          Mesh

·          Single node

·          Hybrid

§          .

·          Most networking software supports all topologies.

·          **BUS TOPOLOGY:-**

·          Bus topology is also called as linear bus. it is the simplest and most common method of computer networking.

·          A bus network is a network architecture in which a set of client are connected to a shared communication line called bus(or)trunk.

·          Terminator is placed at each end of the cable.

·          It is used to remove unsent data from the cable, if the destination device is facility.

·          Data is sent to all the devices connected along backbone cable(trunk).

·          A the message arrives at each devices, it checks the destination address, encoded in the message.

·          If the address matches, it accepts the data. if the address does not match, the device ignores the data.

·          At a time, only one device can send data. due to this, a no. of devices waiting to send data on the bus are more.

·          This results in slow down the performance of a network.

·          When two machines transmit data at the same time, the signals collide, due to this, information is destroyed.

·          This process is called collision. Collision can affect the performance of the network.

·          Ethernet and local talk networks use a linear bus topology.

·          ADVANTAGES:-

·          Easy to implement and extend.

·          Well suited for smaller networks (quick setup).

·          Less expensive than other topologies.

·          Requires less cable as compared to star topology.

·          DISADVANTAGE:-

·          Entire network gets affected, if there is a break in the main cable.

·          Terminators are required at both ends of the backbone cable.

·          Difficult to detect facility device.

·          Limited cable length and no .of stations.

·          Heavy traffic and addition of devices degrades the performance.

·          Difficult to administer/trouble shoot i.e., one virus in the network will affect all of them.

·          Low security because all computer on bus can see data transmission.

·          **RING TOPOLOGY:-**

·          A ring network is a topology of computer networks where each node is connected two other nodes, so as to create a ring (or) circle.

·          Data flows in only one direction i.e., clockwise or anti clockwise.

·          Each device in the ring topology acts as repeater. it amplifies the signal transmission and transmit it to the next device.

·          Ring networks tend to be inefficient when compared to star network because data must travel through many points before reaching its destination.

o      Egg:-if a ring network has eight devices if device 1 wants to transmit data to device 3, data must travel from device 1, through device 2 and then its destination at device 3.

·          The ring topology is used to implement the token ring network at 4or16mbps.

·          In token ring network, each device must have token which allows data to transfer over network.

·          This topology also sends data on priority basis where message of higher priority before message with lower priority.

·          ADVANTAGES:-

·          Very reliable and offers high speed.

·          No terminations are required.

·          Collisions are avoided as only one device is allowed to transmit at a time.

·          Handle large volume of traffic.

·          Provide a good communication over a long distance.

·          DISADVANTAGES:-

·          Data must pass through every computer between sender and recipient therefore, it makes slower.

·          If any of the nodes fail, then the ring is broken and cannot be transmitted successfully.

·          Addition and change of device can affect the network.

·          More cable wires required compared to bus topology.

·          Difficult to trouble shoot the ring.

·          **STAR TOPOLOGY:-**

·          Star networks are one of the most common computer networks’ topologies.

·          In star topology, multiple devices are connected to a central connection point known as hub or switch.

·          Devices’ are attached to the hub by using either copper wire or fiber optic cable.

·          Hub manages all the function of the network and also acts as multiport repeater for flow of data.

·          Hubs can be passive or active. Passive hubs are used as a connection point which route all the traffic towards the device. It does not regenerate or amplify signals.

·          An active hub contains electronic circuits that regenerate and retransmit the information.

·          Active hubs player a major role in Ethernet communications.

·          Data is passed through the hub before reaching the destination.

§                                                                                                                                                                       Egg:-device A wants to transmit data to device B. device A firsts sends data to the hub. if the hub is passive, it rebroadcasts the data to all the device, it regenerates the data before it rebroadcasts’    .

§                                                                                              

·          ADVANTAGE:-

·          Easy to install, configure and manage.

·          Easy to implement and extend, even in large network.

·          Easy to detect faculty device.

·          No problem with collisions of data since each station has its own cable to the server/hub.

·          Hub provides a centralized management.

·          Easy to adjust and add new device to star network without distorting the rest of the network.

·          Failure in any cable will not affect entire network.

·          DISADVANTAGE:-

·          Increased devices cause traffic which makes the network slow.

·          Requires more cable length than a linear topology.

·          Hub/central node failure leads to network failure.

·          More expensive.

·          **MESH TOPOLOGY:-**

·          In mesh topology, every device is connected to each and every node in the network with many redundant interconnection at least two paths to and from every node.

·          A device can send data to all the devices in the network.

·          Data sent by the device can take any possible paths to reach the destination.

·          There are two types of mesh topologies.

·          Full mesh

·          Partial mesh

·          In full mesh topology, each device is connected directly to each other.

·          Full mesh is very expensive to implement but yields greatest amount of residency.

·          In partial mesh topology, some of the devices are connected to all the other, but some of the devices do not exchange data at all.

·          It is less expensive and less redundant compared to full mesh topology.

·          This topology is useful where connections are easily and frequently broken.

·          It is applicable to wireless network, wired network and software interaction.

·          Mesh topology is not used commonly because of its complex structure but it performs well when the devices are spread in a network and do not lie in the same region.

§          E.g.:-wan (wide area network)

§                                                                                              

·          ADVANTAGES:-

·          Entire network does not get affected by one facility device.

·          Facility identification and facility isolation are easy.

·          Centralized management is not required as in star topology.

·          Avoids traffic problems.

·          Privacy (or) security is provided.

o         DISADVANTAGE:-

·          More cabling is required as compared to bus, star and ring topologies.

·          Each link from one device to another requires an individual NIC.

·          Very expensive.

·          Installation and reconfiguration are difficult.

·          Data carrying capacity is underutilized unless all device are transmitting almost constantly.

·          **TREE TOPOLOGY:-**

·          A tree topology is a variation of star.

·          In tree topology, group of star network are connected to the linear bus backbone.

·          The nodes in a tree are linked to a central hub that controls the traffic to the network.

·          The majority of devices are connected to a secondary hub that in turn is connected to the central hub.

·          The central hub in the tree is the active hub which contains a repeater.

·          A repeater regenerates the received message before sending them out and also strings the transmission.

·          Tree topology supports expandability of the network.

·         

·          ADVANTAGE:-

·          Easy to detect a facility device.

·          Easy to expand a network.

·          Point-to-point wiring for each device.

·          DISADVANTAGE:-

·          More difficult to configure as compared to other topologies.

·          Facility in the backbone affects the entire network.

·          More expensive.

·          Overall length of each segment is limited by the type of cabling used.

·          **HYBRID TOPOLOGY:-**

·          Hybrid topology is a combination of different network topologies. it is also known as a special topology.

·          Star, bus & ring are connected to each other to from a hybrid network.

·          The ring network and bus network are connected to another network through point-to-point connection.

·          Star topologies are connected using MAU (multistation access unit) as an unsterilized hub.

·          It has the ability and, maintains the structure of the network.

·          When different types of topologies are combined, their total strength improves the network performance.

·         

·          ADVANTAGE:-

·          Useful for implementing larger networks.

·          Handles larger volume of traffic.

·          Easy to detect and remove facility devices.

·          DISADVANTAGE:-

·          More cabling is required as compare to all other topologies.

·          More expensive than all other topologies.

·          MAU is required.

·          Complex structure.

·          Installation and reconfiguration is difficult.

·          Most connectors are either male that has one (or) more exposed (protruding) pins (or) female that has holes in which the male connector can be inserted.

Quiz

1.       ______ are rules that govern a communication exchange

                a) Media

                b) Criteria

                c) Protocols

                d) all of the above

The _________  is the physical path over which a message travels.

                a) Media

                b) Criteria

                c) Protocols

                d) all of the above

3.  Computer networks are used in ___________________ .

                a) Companies

                b) People

                c) social issues

                d) All of the above

4. In……..topology, each node is connected to every other node by direct links. (a) ring (b)tree (c) mesh (d)bus

5. A concept similar to a telephone network is used in ………topology. (a) ring (b)tree (c) mesh (d)star

6. In tree topology, the central hub is called…..hub. (a) active (b) passive (c) Inactive (d)Live

7. In..topology, if a node fails, the whole network can not function. (a) Ring (b)tree (c)mesh (d) star

8. ……topology used multipoint philosophy. (a)ring (b) bus (c) mesh (d) Hybrid

9. In the case of …., a direct physical connection path is established between two computers. (a) circuit switching (b) packet switching (c) message switching (d) datagram approach

10. …..is more suitable for human communication. (a)circuit switching (b) packet switching (c)message switching (d) datagram approach

11. …is more suitable for computer communications. (a)circuit switching (b) packet switching (c)message switching (d) none

12. the………….layer is the lowest layer in the OSI model. (a) physical (b) transport (c)session (d) application

13. The ………layer is the topmost layer in the OSI model. (a) physical (b) transport (c)session (d) application

14. An Ethernet address can be…….(a) unique (b) Optional (c) duplicated (d) never duplicated

15. In token ring, a special packet containing a ……..goes a rounded the network. (a) data (b) header (c) token (d) bit

In  ________  each node is connected to every other node by direct links

                a) Ring topology

                b) Tree topology

                c) mesh topology

                d) bus topology

A concept similar to a telephone network is used in ___________________ 

                a) Ring topology

                b) Tree topology

                c) Mesh topology

                d) Star topology

In _____________,  if a node fails, the whole network cannot function

                a) Ring topology

                 b) Tree topology

                 c) Mesh topology

                 d) Star topology

_______________   uses  multipoint philosophy

                 a) Ring topology

                 b) Bus topology

                 c) Mesh topology

                 d) Hybrid topology

FAQ’S

Short questions

1.       Define computer network and state its use. (april2010)

2.       Distinguish between circuit switching and packet switching. (march/april 2008, april 2010)

3.       Give some features and applications of Bluetooth technology (april 2010)

4.       Write the applications of WAP. (march/april 2008, april 2010)

Essay type questions

1.       Describe the following network topologies: (i) bus (ii) star (iii)ring. (mar/april 2008,april 2010)

2.       Expalain the concepts of router and routing. (april 2010)