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
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.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#ixzz3l4efzOuKhttp://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.
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.
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.
Wireless
Transmission Media 
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.
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
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
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
