Network Topologies and Communications Media

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What is a Network?

A network consists of two or more computers that are linked together in order to share resources (such as printers, emails and CDs), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.
  

What are their uses?

Benefits of networking :

•  Fewer peripherals needed – By sharing printers and scanners etc. the total cost of ownership of these devices may be lowered
• Increased communication capabilities - via e-mail, chat, blogs etc
• Increased consistency of data by avoiding duplication of data.
• Centralized administration of data and devices
• Lower cost licensing
• Shared processing power  

 

Types of Networks Topologies

Bus topology:

Bus Topology is the simplest of network topologies. In this type of topology, all the nodes are connected to the single cable called bus, by the help of interface connectors. This central cable is the backbone of the network and is known as Bus. Every workstation communicates with the other device through this Bus.

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 (i.e. bus ) 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.

 

 

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Ring Topology:

In Ring Topology, all the nodes are connected to each-other in such a way that they make a closed loop. Each workstation is connected to two other components on either side, and it communicates with these two adjacent neighbors. Data travels around the network, in one direction. Sending and receiving of data takes place by the help of TOKEN.

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.

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Star Topology:

 In Star topology, all the components of network are connected to the central device called a "hub" which may be a hub, a router or a switch. All the workstations are connected to central device with a point-to-point connection. So it can be said that every computer is indirectly connected to every other node by the help of "hub".

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. A sent signal reaches the intended destination after passing through no more than 3-4 devices and 2-3 links. 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. Similarly components can also be removed easily.
3)  Centralized management. It helps in monitoring the network.
4)  Failure of one node or link doesn’t affect the rest of network. At the same time its easy to detect the failure and troubleshoot it.

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.

Mesh topology

A mesh network topology is a decentralized design in which each node on the network connects to at least two other nodes. Unlike nodes in a star topology, which require a router to deliver Internet service, network nodes can "talk" directly to each other without requiring the assistance of an Internet connection.

 

Advantages

▸ The arrangement of the network nodes is such that it is possible to transmit data from one node to many other nodes at the same time.
▸ The failure of a single node does not cause the entire network to fail as there are alternate paths for data transmission.
▸ It can handle heavy traffic, as there are dedicated paths between any two network nodes.
▸ Point-to-point contact between every pair of nodes, makes it easy to identify faults.

Disadvantages

▸ The arrangement wherein every network node is connected to every other node of the network, many connections serve no major purpose. This leads to redundancy of many network connections.
▸ A lot of cabling is required. Thus, the costs incurred in setup and maintenance are high.
▸ Owing to its complexity, the administration of a mesh network is difficult.

Hybrid Topology

Hybrid networks use a combination of any two or more topologies, in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network connected to a tree network is still a tree network topology.

 A hybrid topology is always produced when two different basic network topologies are connected. Two common examples for Hybrid network are: star ring network and star bus network

Advantages and Disadvantages

A hybrid topology combines two or more topologies. This means that this type of topology inherits their advantages and disadvantages. Obviously, the advantages and disadvantages of a hybrid topology are a combination of the merits and demerits of the topologies used to structure it example:

One of its main advantages is that this type of topology is very useful in larger environments like businesses, industries, etc. It also divides certain aspects of the network in a business for better management. It is also very unlikely for the whole network to malfunction if a single node in one of the combined topologies malfunctions.

Different problems vary depending on the combinations. Example: Redundancy and complexity aswel as it being difficult to troubleshoot as some of its major disadvantages.

http://www.buzzle.com/articles/advantages-and-disadvantages-of-different-network-topologies.html#mesh-topology-advantages-disadvantages 
https://en.wikipedia.org/wiki/Network_topology

http://www.ianswer4u.com/2011/05/star-topology-advantages-and.html#ixzz3l4efzOuK
http://www.ianswer4u.com/2011/05/ring-topology-advantages-and.html

Communication Media

What does communication media mean?

Communication media refers to the means of delivering and receiving data or information. In telecommunication, these means are transmission and storage tools or channels for data storage and transmission. 

Different media are employed for transmitting data from one computer terminal to the central computer or to other computer systems inside some kind of network.

There are two forms of communication media:

• Analogue: Includes the conventional radio, telephonic and television broadcasts
• Digital: Computer-mediated communication, computer networking and telegraphy

The most commonly used data communication media include:

• Wire pairs
• Coaxial cable
• Microwave transmission
• Communication satellites
• Fiber optics

The communication media acts as a communication channel for linking various computing devices so that they may interact with each other. 

Contemporary communication media facilitate communication and data exchange among a large number of individuals across long distances via email, teleconferencing, Internet forums, etc. Traditional mass media channels such as TV, radio and magazines, on the other hand, promote one-to-many communication. 

Twisted Pair

Twisted pair is the ordinary copper wire that connects home and many business computers to the telephone company. To reduce crosstalk or electromagnetic induction between pairs of wires, two insulated copper wires are twisted around each other. Each connection on twisted pair requires both wires. Since some telephone sets or desktop locations require multiple connections, twisted pair is sometimes installed in two or more pairs, all within a single cable. For some business locations, twisted pair is enclosed in a shield that functions as a ground. This is known as shielded twisted pair (STP). Ordinary wire to the home is unshielded twisted pair (UTP).


Coaxil Cable

Coaxial cable conducts electrical signal using an inner conductor (usually a solid copper, stranded copper or copper plated steel wire) surrounded by an insulating layer and all enclosed by a shield, typically one to four layers of woven metallic braid and metallic tape. The cable is protected by an outer insulating jacket. Normally, the shield is kept at ground potential and a voltage is applied to the center conductor to carry electrical signals. The advantage of coaxial design is that electric and magnetic fields are confined to the dielectric with little leakage outside the shield. Conversely, electric and magnetic fields outside the cable are largely kept from causing interference to signals inside the cable

Coaxial cable is used as a transmission line for radio frequency signals. Its applications include feedlines connecting radio transmitters and recievers with their antennas, computer network(internet)connections, digital audio, and distributing cable television signals. One advantage of coaxial over other types of radio transmission line is that in an ideal coaxial cable the electromagnetic field carrying the signal exists only in the space between the inner and outer conductors. This allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines. Coaxial cable also provides protection of the signal from external electromagnetic interference.

Fiber-Optic Cable 

An optical fiber is a glass or plastic conductor that transmits information using light. A fiber-Optic cable has one or more optical fibers enclosed in a jacket. Fiber-optic cables are not affected by EMI or RFI because they are made of glass. The signal are converted to light pulses to enter the cable and converted back into electrical signals when they leave it. This means that fiber-optic cable can deliver signals that are clearer, that can go farther, and that have greater bandwidth than cable made of copper or other metals. Fiber-optic cable can reach distances of several miles or kilometers before the signal needs to be regenerated. Fiber-optic cable usually is more expensive to use than copper cable, and the connectors are more costly and harder to assemble. Common connectors for fiber-optic networks are SC, ST, and LC. These three types of fiber-optic connectors are half-duplex, which allows data to flow in only one direction. Therefore, two cables are needed.

These are the two types of glass fiber-optic cable:

·         Multimode is cable that has a thicker core than single-mode cable. It is easier to make, can use simpler light sources (LEDs), and works well over distances of a few

Kilometres or less

              

·         Single-mode is cable that has a very thin core. It is harder to make, uses lasers as a

             light source, and can transmit signals dozens of kilometers with ease.

Fiber-optic cable has many advantages over metal communication lines:

·         The bandwidth on fiber-optic cables is much greater than metal cables. This means more data can be carried.

·         Fiber-optic cables are less susceptible to interference as opposed to metal cables

·         Fiber-optic cables are thinner and lighter than other cables

·         Transmits data digitally rather than analogically

The main disadvantage of fiber optics is that the cables are expensive to install. In addition, they are more fragile than wire and are difficult to splice.

Fiber optics is a particularly popular technology for local-area networks. In addition, telephone companies are steadily replacing traditional telephone lines with fiber optic cables. In the future, almost all communications will employ fiber optics.

References

www.webopedia.com/fiberoptics

Textbook I.T Essentials Pc hardware and Software

Wireless Transmission Media 

Wireless transmission is a form of unguided media. Wireless communication involves no physical link established between two or more devices, communicating wirelessly. Wireless signals are spread over in the air and are received and interpreted by appropriate antennas.

When an antenna is attached to electrical circuit of a computer or wireless device, it converts the digital data into wireless signals and spread all over within its frequency range. The receptor on the other end receives these signals and converts them back to digital data.

Infrared

Infrared is a wireless transmission media that sends signals using infrared light waves. Infrared transmission requires a line of sight transmission, that is the sender and receiver must be aligned so that nothing obstructs the path of infrared light wave.

                            

Communication Satellite

This is a space station that receives microwave signals from an earth-based station, amplifies the signals, and broadcasts the signal back over a wide area to any number of earth-based station. A transmission from the earth to a satellite is called an uplink; a transmission from a satellite to an earth station is called a downlink. Communication satellites are used in application such as air navigation, television and radio broadcasting , videoconferencing and paging.

Design Team

Kush Maharaj  

Nadhiren Naidoo 

 Adhikar Ramsarup 

 Dillon Nundlel 

Deevesh Rampersadh 

  Thiveshin Moodley