Pros and Cons of Light Wave Transmission

Light Wave Transmission

A modern application is to connect the LANs in two buildings via lasers mounted on their rooftops.
So each building needs its own laser and its own photo detector.

PROS
Lasers are unidirectional with high bandwidth and low cost.
It is also easy to install and does not require an FCC (Federal Communications Commission) license.

The laser’s strength a very narrow beam is its weakness but 1mm wide beam at a target 1mm wide 500 meters away requires.

Cons
A disadvantage is that laser beams cannot penetrate rain or thick fog.

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Pros and Cons of Radio waves

Radio waves  PROS and Cons

Radio waves are used every day in our lives, as they are used to broadcast everything that you hear on the radio and see on your television. They have the lowest frequency and the highest wavelength of the electromagnetic spectrum, and are the least potentially dangerous. There are no real health problems directly associated with radio waves. (Unless you blow your car up with the volume of your radio, but that has to do with sound waves and amplitude, and we don't have any control over what you set that to.) They are the lowest on the electromagnetic spectrum, and are just below microwaves. With these waves, it is possible to communicate with people around the world, and even to other planets in space! One day, some radio signals that we have sent off into space may yet reach another planet with life. Here are some pros and cons of using radio waves.

PROS

    They can be used for communication (This one's for you, phone companies.)
    They do not harm living organisms at all.
    They are available in a wide range of frequencies.
    They can be used to save lives. (For example, radioing someone if you are stuck at sea and need to be rescued.)
    Sometimes used for radar.

cons

    Interference from other radio waves can be a problem.
    Range can also be a problem. (Higher Frequencies = More Range)

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Pros and Cons of Message Switching

Message Switching

ADVANTAGES
1. It provides efficient traffic management by assigning priorities to the messages to be switched.
2. No physical connection is required between the source & destination as it is in circuit switching.
3. It reduces the traffic congestion on network because of store & forward facility. Each node can store the message until communication channel becomes available.
4. Channels are used effectively and network devices share the data channels.
5. It supports the message length of unlimited size.

DISADVANTAGES of Message Switching
1. As message length is unlimited, each switching node must have sufficient storage to buffer message.
2. Storing & forwarding facility introduces delay thus making message switching unsuitable for real time applications like voice and video.

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Pros and Cons of Packet Switching

Packet Switching
ADVANTAGES
1. More efficient use of overall network bandwidth due to flexibility in routing the smaller packets over shared links.
2. It allows multiplexing; different users, or different processes from the same user, can communicate at the same time.
3. Cheaper to build as less equipment is needed.

DISADVANTAGES OF PACKET SWITCHING
1. Longer delays in receiving messages due to the time required to package and route packets
2. Potential for network security risks due to the use of shared physical links

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Pros and Cons of Circuit Switching

Circuit Switching
ADVANTAGES
Highly reliable

DISADVANTAGES
Requires an initial channel set up that is usually time-consuming

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Unshielded Twisted Pair Cables Vs. Shielded Twisted Pair Cables

Shielded Twisted Pair Cables
Pros and Cons
The protective casing/shielding of STP cables works in connection with the other crosstalk-eliminating techniques implemented in Twisted Pair cables, giving it a performance edge over other types like UTP and coaxial cables.

Properly installed STP cables are the most secure of all.

However, the operation of STP cables is not that simple. First of all, they are bulky, as well as fragile. They need to be correctly installed and then regularly maintained, taking into account physical factors like their bending radius and maximum tension, otherwise they could easily get damaged.

They are costlier than other types of cables, and additionally, the cost of their installation and maintenance is high.

STP cables need to be properly grounded. If this is not taken care of, the shielding will have the opposite effect; rather than eliminating cross talk, the cable will start attracting stray signals and interference.

Unshielded Twisted Pair Cables

Since these cables are inexpensive, less bulky, perform satisfactorily when used to provide basic connectivity, are easy to install, and also require less maintenance, they are very popular.

Various categories of UTP cables are available, which have different specifications, including data speed. UTP cables have the ability to match STP cables' data transmission rates.

In the absence of casing, twisted pairs alone are not as capable of blocking out cross talk, and hence, UTP cables depend on other techniques of signal balancing, including the use of devices like filters and baluns.

Due to the fact that they are susceptible to noise, they have limited applications.
Read more at Buzzle: http://www.buzzle.com/articles/comparison-between-stp-cable-and-utp-cable.html

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Pros and Cons of Fiber Optic Cable

Fiber Optic Cable

Advantages

    It can handle much higher bandwidth than copper. Due to the low attenuation, repeaters are needed only about every 30 Km on fiber lines, versus about every 5 km for copper.
    Fiber is not affected by power surges, electromagnetic interference, or power failures. Nor is it affected by corrosive chemicals in the air, making it ideal for factory environments where electrical interference is very high.
    Fiber is lighter than copper. One thousand twisted pairs copper cables of 1 km long weigh 800 kg. But fibers have only 100 kg.
    Fibers do not leak light and are quite difficult to tap. This gives them excellent security against potential wire-tappers.

Disadvantages

    Fiber is an unfamiliar technology requiring skills which may not be easily available.
    Since optical transmission is inherently unidirectional, two-way communication requires either two fiber cables or two frequency bands on one fiber.
    Fiber interfaces cost more than electrical interfaces.

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Pros and Cons of Coaxial Cable

Coaxial Cable

Advantages

    It has better shield against electromagnetic interference than twisted pair cable, so it can span longer distance at higher data bits per second (bps).
    It can be used for both analog and digital data transmissions. For analog data transmission, 75-ohm broadband coaxial is used and for digital transmission, 50 – ohm baseband cable is used.
    It is inexpensive as compared to twisted pair wires and UTP cables but easy to handle.

Trade-off between Coaxial Cable and Twisted-pair wiring
Following factors give the comparison between the coaxial cable and twisted pair wiring as transmission media.
Cost
In general, coaxial cable is more expensive by a factor of two or three, than twisted pair, and more expensive by a smaller factor than shielded twisted pair.
Data rate
The difference between coaxial and twisted pair cable is more apparent in the data rate that they support. For comparable distances to be spanned, twisted pair will typically be suitable for data rates of at least an order of magnitude less. If the data rate of choice is 1 – Mbps, then either coaxial cable or twisted pair will suffice at distance out to several hundred meters.
Security
Cables that employ copper conductors can easily be breached by listening equipment. If the main consideration is security, then fiber cable is the only choice to avoid espionage. However it is to be remembered that no system can ever be perfectly secure. Even fiber-optic lines can be tapped without detection.
Electromagnetic compatibility
Coaxial cable emits less radiation which may cause less interference with the communication equipment as compared to twisted wires.
Disadvantages

    More expensive to install compare to twisted pair cable.
    The thicker the cable, the more difficult to work with.

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Pros and Cons of Twisted Pair

Twisted Pair

Advantages

    Being the oldest method of data transmission, trained manpower to repair and service this media of communications are easily available.
    In a telephone system, signals can travel several kilometers without amplification when twisted pair wires are used.
    These media can be used for both analog and digital data transmission. The bandwidth depends on the thickness of the wire and the distance travelled, but several megabits per second can be achieved for a few kilometers in many cases.
    It is the least expensive media for transmission for short distances.
    If a portion of a twisted-pair cable is damaged, the entire network is not shut down as it may be the case with coaxial cable.

Disadvantages

    Easily pick up noise signals which results in higher error rates when the line length exceeds 100 meters.
    Being thin in size, it is likely to break easily.
    It can support 19,200 bps up to 50 feet on RS-232 port.

Shielded wire is used in an electrically noisy environment to limit the effects of noise absorption. Twisted – pair wiring is more commonly used for LAN media. The twisted pair version of Ethernet is designated as 10BASE-T, in which 10 refers to the Ethernet rate of 10 Mbps.
Twisted pair cabling comes in several varieties. In computer networks, two of these are important. Category 3 twisted pair’s cable consists of two insulated wires gently twisted together. Four such pairs are typically grouped together in a plastic sheath for protection and to keep the eight wires together. Another more advanced category, 5 twisted pairs were introduced. They are similar to category 3 pairs, but with more twist per centimeter, which results in less crosstalk and better quality signal over longer distances, making them more suitable for high speed computer communication

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Advantages And Disadvantages Of Tcp/ip and Osi Model

Advantages And Disadvantages Of Tcp/ip Model
Advantages:

    It can be used to establish/set up connection b/w different types of computers.
    It operates/works independently of the operating system.
    It support for a number of routing-protocols.
    It enables the internetworking between the organizations.
    It has a scalable, client-server architecture.

Disadvantages:

    It is complex to set up & manage.
    IPX is faster than TCP/IP model.
    The shallow/overhead of TCP/IP is higher-than ipx.


Advantages And Disadvantages Of Osi Model

Advantages:

    It provides wide variety of choice.
    It does not depend or rely on a specific computer system.
    It interprets the product functionality at each-stage.
    It encrypts the data for security purpose.
    It is easy to add multiple-network models.

Disadvantages:

    Many applications do not require/need the data integrity, which is provided by OSI-model.
    In order to fast set up OSI requires agreement b/w three-parties: users & service provider.
    Complex.
    This model is not adapted at all to telecommunication applications on computer.

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The Physical Layer

The physical layer

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Introduction to Computer Networks

Introduction to computer networks

Why we use computer networks?

1. Easily share documents
2. Share resources.
3. To communicate with other network users( Eg. E-mail, IM, video-conferencing ) .

If my network is connected to the Internet, I can,

1. Shopping online
2. Use online banking
3. Access large scale of information.

Business Applications of Networks

 

The client server model involves requests and replays.

Some home network applications with examples.

 - Access to remote information (VNC, Team-viewer)

 - Person to person communication(Skype, IM)

 - Interactive entertainment.

 - Electronic commerce.

In peer to peer network there are no fixed servers and clients.

Forms of e-commerce with examples.

1. Business to Consumer (Buy books form amazon.com)

2. Business to Business (Car manufacturer company buy Tires from tire company) 

3. Government to Consumer(get Vehicle renewal license online)

4. Consumer to Consumer(ikman.lk) 

5. Peer to Peer (Bit torrent, File sharing...)

Broadcast Networks(Transferring a message to all recipients simultaneously).

1. Broadcast Links.

2. Point to Point links

Broadcast links with their distances.

----------------------------------------------------------------------------
Inter process                        | Processors located |
distance                               | in same                   | Eg:
----------------------------------------------------------------------------
1 m                                      | Squire meter (PAN) Bluetooth          
10 m                                    | Room            (LAN)
100 m                                  | Building        (LAN)
1 KM                                   | Campus         (LAN)
10 KM                                 | City               (MAN)
100 KM                               | Country         (WAN)
1000 KM                             | Continent       (WAN)
10,000 KM                          | Planet             (Internet)
----------------------------------------------------------------------------

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