Topologies

                                                      Topology

The topology of a network refers to the configuration cables, computers. Topology is the way in which the computers are  connected to form a network.

• it  also refers which network of computers is connected.
• each topology is suited to specific tasks and has its own advantage and disadvantages.

Different Network Topologies

The major topologies are

•          Bus

•          Ring

•          Star

•          Tree

•          Mesh

•          Hybrid

Choice of Topology         

Depends Upon

•          Type and number of equipments being used

•          Planned applications and rate of data transfer

•          Required response time

•          Cost

Bus Topology

It is also called as Linear Bus Topology. It contains a long cable called from which different computers are connected. Generally coaxial cable are used.

this Cable contains a terminator at each end. All nodes are connected by using tapping process. Here Node means system or work station and perpherals.

Advantages:

1. easy to connect a computer or perpheral to a bus topology.
2. easy to use and understand
3. less no of cables are required
4. low cost and simple network to connect multiple nodes
5. easy to expand the network, using repeaters.

Disadvantages

1. entire network shut downs if there is any break(failure) in the main cable
2. terminators are required at both ends of the main cable
3. computers become slow down by heavy network traffic with a lot of devices.
4. diffucult to identify the problem if any network interrupts
5. low security (all computers on the bus can see(access) all the tranmission)
6. one virus in the network will affect all of them
7. limited cable length and no of stations

Star Topology

•          Devices are connected by cable segments to a

   centralized device (i.e. hub)

Characteristics of Star Topology

•          A star topology is designed with each node(file server, work station, and peripherals) connected directly to a central network hub or concentrator.

•          Data on a star network passes through the hub before continuing to its destination.

•          The hub manages and controls all functions of the network and it also acts as a repeaters for the data flow.

•          Twisted pairs are used for this configuration, it can be also used coaxial or fiber optic cable. If one device wants to send data to another, it sends the data to the controller, which then transmits the data to other device

•             Computers are connected by cable segments to a

    centralized hub

•             Signal travels through the hub to all other computers

•             Requires more cable

•             If hub goes down, entire network fails to function

•             If a computer goes down, the network functions normally

•             Most scalable and reconfigurable of all topologies

Star Topology- 

Advantages

•             The failure of a single device or cable doesn’t bring down

     the entire network

•            The centralized networking equipment can reduce costs in

    the long run by making network management much easier

•            It allows several cable types in same network with a hub

   that can accommodate multiple cable types

Star Topology - Disadvantages

•            Failure of the central device (hub) causes the whole

         network failure

•            Expensive than bus topology

RING TOPOLOGY

Characteristics of Ring Topology

•          The computers are connected to end to end as shown in fig.10 to form a circular path

•          The data has to travel through the circular path from one computer to another till it reaches the destination system

•          If more devices are connected network becomes slower

•          The break down of a system can halt the entire network

Advantages

•               One  device  cannot monopolize the network

•               Continues  to function after many nodes are  

      connected but the speed will be slow

 Disadvantages

•            Failure of one device can affect the whole network

             difficult  to troubleshoot

•           Adding and removing devices disrupts the network

1.       ______ are rules that govern a communication exchange

                a) Media

                b) Criteria

                c) Protocols

                d) all of the above

2. 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

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

                a) Ring topology

                b) Tree topology

                c) mesh topology

                d) bus topology

2. 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

4. _______________   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)