The Advantages Of Bus Topology

Published Date: 02 Nov 2017

Introduction

Nowadays computer is available in many office and homes, therefore there is a need to share data and programs among various computers. With the advancement of data communication facilities the communication between computers has increased and thus it has extended the power of computer beyond computer room. Now a user sitting at one place and can communicate with any computers of any remote site with communication channel.

Data communication is referred as the transfer of information between two points, either via an analogue (sine wave) electrical signal, or digital (binary) signal via electrical pulses or optically via light pulses.

A network topology describes the arrangement of systems on a computer network. It defines how the computers, or nodes, within the network are arranged and connected to each other.

Transmission media means, through which data is transformed from one place to another place is called transmission or communication media.

The aim of this assignment is to do a research on the types of network topology available and identify the networks and recommend to a management, and discuss both transmission media in detail with examples.

Question 1

Network topologies

Network topologies are categorized into the following basic types:

� Bus

� Ring

� Star

� Tree

Bus Topology

Bus networks use a common backbone to connect all devices. A single cable functions as the backbone, share communication medium that devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message.

Ethernet bus topologies are relatively easy to install and don't require much cabling compared to the alternatives. However, bus networks work best with a limited number of devices. If more than a few dozen computers are added to a network bus, performance problems will likely result. In addition, if the backbone cable fails, the entire network effectively becomes unusable.

Advantages of Bus Topology

1) It is easy to set-up and extend bus network.

2) Cable length required for this topology is the least compared to other networks.

3) Bus topology costs very less.

4) Linear Bus network is mostly used in small networks. Good for LAN.

Disadvantages of Bus Topology

1) There is a limit on central cable length and number of nodes that can be connected.

2) Dependency on central cable in this topology has its disadvantages.If the main cable encounters some problem, whole network breaks down.

3) Proper termination is required to dump signals. Use of terminators is must.

4) It is difficult to detect and troubleshoot fault at individual station.

5) Maintenance costs can get higher with time.

6) Efficiency of Bus network reduces, as the number of devices connected to it increases.

7) It is not suitable for networks with heavy traffic.

8) Security is very low because all the computers receive the sent signal from the source

Ring Topology

In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction either "clockwise" or "counterclockwise". A failure in any cable or device breaks the loop and can take down the entire network.

To implement a ring network, one typically uses FDDI, SONET, or Token Ring technology. Ring topologies are found in some office buildings or school campuses.

Advantages of Ring Topology

1) This type of network topology is very organized. Each node gets to send the data when it receives an empty token. This helps to reduces chances of collision. Also in ring topology all the traffic flows in only one direction at very high speed.

2) Even when the load on the network increases, its performance is better than that of Bus topology.

3) There is no need for network server to control the connectivity between workstations.

4) Additional components do not affect the performance of network.

5) Each computer has equal access to resources.

Disadvantages Of Ring Topology

1) Each packet of data must pass through all the computers between source and destination. This makes it slower than Star topology

2) If one workstation or port goes down, the entire network gets affected.

3) Network is highly dependent on the wire which connects different components.

4) MAU�s and network cards are expensive as compared to Ethernet cards and hubs.

Star Topology

Many home networks use the star topology. A star network features a central connection point called a "hub node" that may be a network hub, switch router. Devices typically connect to the hub with Unshielded Twisted Pair Ethernet.

Compared to the bus topology, a star network generally requires more cable, but a failure in any star network cable will only take down one computer's network access and not the entire LAN. But if the hub fails, the entire network also fails.

Advantages of Star Topology

1) As compared to Bus topology it gives far much better performance, signals don�t necessarily get transmitted to all the workstations. Performance of the network is dependent on the capacity of central hub.

2) Easy to connect new nodes or devices. In star topology new nodes can be added easily without affecting rest of the network.

3) Centralized management. It helps in monitoring the network.

Disadvantages of Star Topology

1) Too much dependency on central device has its own drawbacks. If it fails whole network goes down.

2) The use of hub, a router or a switch as central device increases the overall cost of the network.

3) Performance and as well number of nodes which can be added in such topology is depended on capacity of central device

Tree Topology

Tree topologies integrate multiple star topologies together onto a bus. In its simplest form, only hub devices connect directly to the tree bus and each hub functions as the root of a tree of devices. This bus/star hybrid approach supports future expandability of the network much better than a bus which limited in the number of devices due to the broadcast traffic it generates or a star which limited by the number of hub connection points alone.

Advantages of Tree Topology

1.Expansion of Network is possible and easy.

2. Error detection and correction is easy.

3. Each segment is provided with dedicated point-to-point wiring to the central hub.

4. If one segment is damaged, other segments are not affected.

Disadvantages of Tree Topology

1. Because of its basic structure, tree topology, relies heavily on the main bus cable, if it breaks whole network is crippled.

2. As more and more nodes and segments are added, the maintenance becomes difficult.

3. Scalability of the network depends on the type of cable used.

Question 2

1. TRANSMISSION MEDIA

This means through which data is transformed from one place to another is called transmission or communication media. There are two categories of transmission media used in computer communications.

� GUIDED MEDIA

� UNGUIDED MEDIA

1. GUIDED MEDIA:

Bounded media are the physical links through which signals are confined to narrow path. These are also called guide media. Bounded media are made up of external conductor usually copper bounded by jacket material. Bounded media are great for LABS because they offer high speed, good security and low cast. However, some time they cannot be used due distance communication. Three common types of bounded media are used of the data transmission. Which is ;

� Coaxial Cable

� Twisted Pairs Cable

� Fiber Optics Cable

COAXIAL CABLE:

Coaxial cable is very common & widely used commutation media. For example TV wire is usually coaxial.

Coaxial cable gets its name because it contains two conductors that are parallel to each other. The center conductor in the cable is usually copper. The copper can be either a solid wire or stranded martial.

Outside this central Conductor is a non-conductive material. It is usually white, plastic material used to separate the inner Conductor form the outer Conductor. The other Conductor is a fine mesh made from Copper. It is used to help shield the cable form EMI.

Outside the copper mesh is the final protective cover.The actual data travels through the center conductor in the cable. EMI interference is caught by outer copper mesh. There are different types of coaxial cable vary by gauge & impedance.

Gauge is the measure of the cable thickness. It is measured by the Radio grade measurement, or RG number. The high the RG number, the thinner the central conductor core and the lower the thicker of the core.

CHARACTERISTICS OF COAXIAL CABLE

� Low cost

� Easy to install

� Up to 10Mbps capacity

� Medium immunity form EMI

� Medium of attenuation

ADVANTAGES COAXIAL CABLE

� Inexpensive

� Easy to wire

� Easy to expand

� Moderate level of EMI immunity

DISADVANTAGE COAXIAL CABLE

Single cable failure can take down an entire network

Twisted Pair Cable

The most popular network cable is Twisted pair cable. It is light weight, easy to install, inexpensive and support many different types of network. It also supports the speed of 100 mps. Twisted pair cabling is made of pairs of solid or stranded copper twisted along each other. The twists are done to reduce vulnerably to EMI and cross talk. The number of pairs in the cable depends on the type. The copper core is usually 22-AWG or 24-AWG, as measured on the American wire gauge standard. There are two types of twisted pairs cabling

1. Unshielded twisted pair (UTP)

2. Shielded twisted pair (STP)

1. Unshielded twisted pair (UTP)

UTP is more common. It can be either voice grade or data grade depending on the condition. UTP cable normally has an impedance of 100 ohm. UTP cost less than STP and easily available due to its many use. There are five levels of data cabling

Characteristics of UTP

� low cost

� easy to install

� High speed capacity

� High attenuation

� Effective to EMI

� 100 meter limit

Advantages of UTP

� Easy installation

� Capable of high speed for LAN

� Low cost

Disadvantages of UTP

� Short distance due to attenuation

2. Shielded twisted pair (STP)

It is similar to UTP but has a mesh shielding that�s protects it from EMI which allows for higher transmission rate.

Characteristics of STP

� Medium cost

� Easy to install

� Higher capacity than UTP

� Higher attenuation, but same as UTP

� Medium immunity from EMI

� 100 meter limit

Advantages of STP:

� Shielded

� Faster than UTP and coaxial

Disadvantages of STP:

� More expensive than UTP and coaxial

� More difficult installation

� High attenuation rate

Fiber Optics

Fiber optic cable uses electrical signals to transmit data. It uses light. In fiber optic cable light only moves in one direction for two way communication to take place a second connection must be made between the two devices. It is actually two stands of cable. Each stand is responsible for one direction of communication. A laser at one device sends pulse of light through this cable to other device. These pulses translated into �1�s� and �0�s� at the other end.

In the center of fiber cable is a glass stand or core. The light from the laser moves through this glass to the other device around the internal core is a reflective material known as CLADDING. No light escapes the glass core because of this reflective cladding.

Fiber optic cable has bandwidth more than 2 Gigabytes per Second.

Characteristics Of Fiber Optic Cable:

� Expensive

� Very hard to install

Advantages Of Fiber Optic Cable:

� Fast

� Low attenuation

� No EMI interference

Disadvantages Fiber Optics:

� Very costly

� Hard to install

2. UNGUIDED MEDIA

Unguided Transmission Media

Transmissions and receptions are achieved by means of an antenna and can be

Directional

Point-to-point focused beams employing high frequencies.

Omnidirectional

Waves propagating in all directions using signals of lower frequencies.

Terrestrial Microwave

� Microwaves bend with the curvature of the earth

� Effective distance of microwave antenna

� Weather conditions and interference are a factor

� Used mainly for distance communication of voice and television transmission, and for short-point-to-point communications.

Satellite Microwave

A communication satellite:

� Is used for link ground stations

� Operates on a number of frequency bands, called transponder channels.

� Receives transmissions on one frequency band (uplink), and transmits on another frequency (downlink).

� Satellite period of rotation equals the earth's period of rotation At height of 34,784 km.

� Used for TV distribution, long-distance telephone, and business networks

Radio

Unlike microwave transmission that is directional, radio transmission is omnidirectional. The signals need simpler antennas.

Conclusion

As conclusion for Question 1, I will choose and recommend star topology to my company management KK & Company because since it is a newly formed company there are not many staff working and a small amount of system only. It will be quite better if star topology is use in the company. Many organization use the star network or a variation of it in a time-sharing system, in which several users are able to share a central processor. In a time-sharing setup, each terminal receives a fixed amount of the CPU�s time, called a time slice. By establishing Time-sharing, many people in a large organization can use a centralized computing facility. Star network is frequently used in a LAN to connect several microcomputers to central unit that works as a communication controller. Another common use of the star network is the feasibility of connecting several microcomputers to a mainframe computer that allows access to an organization�s database.

In question 2 we discuss about transmission media that are used to convey information can be classified as guided or unguided. Guided media provide a physical path along which signal is propagated, while unguided media is wireless, which will employ antennas.