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Sunday, August 29, 2010

RING TOPOLOGY

Also known as a ring network, the ring topology is a type of computer network configuration where each network computer and device are connected to each other forming a large circle (or similar shape). Each packet is sent around the ring until it reaches its final destination. Today, the ring topology is seldom used.


Because a ring topology provides only one pathway between any two nodes, ring networks may be disrupted by the failure of a single link. A node failure or cable break might isolate every node attached to the ring.


Advantages

  • Very orderly network where every device has access to the token and the opportunity to transmit
  • Performs better than a star topology under heavy network load
  • Can create much larger network using Token Ring
  • Does not require network server to manage the connectivity between the computers

Disadvantages

  • One malfunctioning workstation  can create problems for the entire network
  • Moves, adds and changes of devices can affect the network
  • Network adapter cards is much more expensive than Ethernet cards and hubs
  • Much slower than an Ethernet network under normal load

BUS TOPOLOGY

In local area networks where bus topology is used, each machine is connected to a single cable. Each computer or server is connected to the single bus cable through some kind of connector. A terminator is required at each end of the bus cable to prevent the signal from bouncing back and forth on the bus cable. A signal from the source travels in both directions to all machines connected on the bus cable until it finds the MAC address or IP address on the network that is the intended recipient. If the machine address does not match the intended address for the data, the machine ignores the data. Alternatively, if the data does match the machine address, the data is accepted. Since the bus topology consists of only one wire, it is rather inexpensive to implement when compared to other topologies. However, the low cost of implementing the technology is offset by the high cost of managing the network. Additionally, since only one cable is utilized, it can be the single point of failure. If the network cable breaks, the entire network will be down.

TYPES OF TOPOLOGY

TYPES
  1. BUS 
  2. RING
  3. STAR
  4. MESH
  5. HYBRID
  6. FULLY CONNECTED
  7. CELLULAR

NETWORK TOPOLOGY

In computer networking, topology refers to the layout of connected devices.
Network topology is defined as the interconnection of the various elements (links, nodes, etc.) of a computer network. Network Topologies can be physical or logical. Physical Topology means the physical design of a network including the devices, location and cable installation.







Wednesday, August 25, 2010

TYPES OF OFC

On the basis of fibre(core) OFC is of two types

  1. Single Mode 
  2. Multi Mode
SINGLE MODE

Single-mode fiber is a type of fiber optic cable through which only one light signal can travel at a time.


MULTI MODE


Multi-mode fiber is a type of fiber optic cable which is thick enough for light to follow several paths through the code.

CO-AX Vs OFC

BRIEF OVER VIEW OF FIBER OPTIC CABLE ADVANTAGES OVER COPPER:

SPEED: Fiber optic networks operate at high speeds - up into the gigabits
BANDWIDTH: large carrying capacity
DISTANCE: Signals can be transmitted further without needing to be "refreshed" or strengthened.
RESISTANCE: Greater resistance to electromagnetic noise such as radios, motors or other nearby cables.
MAINTENANCE: Fiber optic cables costs much less to maintain.


Sunday, August 22, 2010

OPTICAL FIBRE CABLE

An optical fiber cable is a cable containing one or more optical fibers. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube suitable for the environment where the cable will be deployed.

DESIGN

OFC  made up of 3 layers.
  1. fibre or core
  2. cladding
  3. outer jacket

In practical fibers, the cladding is usually coated with a tough resin buffer layer, which may be further surrounded by a jacket layer, usually plastic. These layers add strength to the fiber but do not contribute to its optical wave guide properties. Rigid fiber assemblies sometimes put light-absorbing ("dark") glass between the fibers, to prevent light that leaks out of one fiber from entering another. This reduces cross-talk between the fibers, or reduces flare in fiber bundle imaging applications.                                                                                                                                              

The advantages of using fibre optics


Because of the Low loss, high bandwidth properties of fiber cable they can be used over greater distances than copper cables, in data networks this can be as much as 2km without the use of repeaters. Their light weight and small size also make them ideal for applications where running copper cables would be impractical, and by using multiplexors one fibre could replace hundreds of copper cables. This is pretty impressive for a tiny glass filament, but the real benefits in the data industry are its immunity to Electro Magnetic Interference (EMI), and the fact that glass is not an electrical conductor. Because fibre is non-conductive, it can be used where electrical isolation is needed, for instance between buildings where copper cables would require cross bonding to eliminate differences in earth potentials. Fibres also pose no threat in dangerous environments such as chemical plants where a spark could trigger an explosion. Last but not least is the security aspect, it is very, very difficult to tap into a fibre cable to read the data signals

UNSHIELDED TWISTED PAIR CABLE

UTP (Unshielded Twisted Pair)

UTP, or Unshielded Twisted Pair, is a type of cable used in telecommunications and computer networks. It consists of different numbers of copper wire that have been twisted into matching pair. It differs from screened and shielded twisted pair, in that the individual pair are not protected with additional protection from interference. Each copper wire is insulated, and the groups of twisted pair have a sheathing holding them together, but no additional insulation is provided. UTP comes in many different types and sizes, and is primarily used as node cabling, meaning it runs from a backbone unit to the individual components on the network.

Types


UTP comes in different types called Categories, often abbreviated as "Cat". The most common are Cat 3, Cat 5e, and Cat 6. The higher the category number, the more twists per foot in the pair, and the better protection from interference. Cat 3 is usually used for home telephone systems. Cat 5e is the industry standard for computer networks and large telephone systems. Cat 6 is an improvement on Cat 5e and is starting to become the favorite for new installs due to its increased speed and protection from interference

TWISTED PAIR CABLE

A type of cable that consists of two independently insulated wires twisted around one another. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. While twisted-pair cable is used by older telephone networks and is the least expensive type of local-area network (LAN) cable, most networks contain some twisted-pair cabling at some point along the network.

OR

Twisted pair cable consists of a pair of insulated wires twisted together. It is a cable type used in telecommunication for very long time. Cable twisting helps to reduce noise pickup from outside sources and crosstalk on multi-pair cables.

 TYPES
  1. STP
  2. UTP
STP (shielded twisted pair)


Short for Shielded Twisted-Pair cable, STP is a type of cable originally developed by IBM for Token Ring that consists of two individual wires wrapped in a foil shielding to help provide a more reliable data communication. Shielded twisted pair is a special kind of copper telephone wiring used in some business installations. An outer covering or shield is added to the ordinary twisted pair telephone wires; the shield functions as a ground.

Thursday, August 19, 2010

COAXIAL CABLE

Coaxial cable, or coax, is an electrical cable with an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis.

Coaxial cable design choices affect physical size, frequency performance, attenuation, power handling capabilities, flexibility, strength and cost. The inner conductor might be solid or stranded; stranded is more flexible. To get better high-frequency performance, the inner conductor may be silver plated. Sometimes copper-plated iron wire is used as an inner conductor.

Coaxial cable is still the most common means of data transmission over short distances. This established technology provides a wide range of products suitable for most electronic systems. As computer speed increases and services require more data bits per second, the upper limits of coaxial cable's carrying capacity are being reached. Fiber-optic cable has replaced coax in many applications.


Coaxial cable is still the most common means of data transmission over short distances. This established technology provides a wide range of products suitable for most electronic systems. As computer speed increases and services require more data bits per second, the upper limits of coaxial cable's carrying capacity are being reached. Fiber-optic cable has replaced coax in many applications.

TRANSMISSION MEDIA

A transmission medium (plural transmission media) is a material substance (solid, liquid, gas, or plasma) which can propagate energy waves. For example, the transmission medium for sound received by the ears is usually air, but solids and liquids may also act as transmission media for sound.


The term transmission medium can also refer to the technical device which employs the material substance to transmit or guide the waves. Thus an optical fiber or a copper cable can be referred to as a transmission medium.

A transmission medium can be classified as a:
Bounded/Guided   Waves are guided along a solid medium such as a transmission line.
  1. CO-AX(Coaxial cable)
  2. Twisted Pair
  3. Optical fibre cable
Unbounded/Unguided  Transmission and reception are achieved by means of an antenna.
  1. Microwave
  2. radiowave
  3. Infra red Ray
  4. Xray
  5. Gamma ray etc.

NETWORK ELEMENTS

There are basic three network elements to develop a Computer Network.
  1. NETWORK SERVICES
  2. COMMUNICATION PATH
  3. COMMUNICATION PROTOCOL
NETWORK SERVICES

Network services are the foundation of a networked computing environment. Generally network services are installed on one or more servers to provide shared resources to client computers

Common network services include:


Application
Authentication servers
Directory services
Dynamic Host Configuration Protocol (DHCP)
DNS
e-Mail/Message
Print
File service
etc.

Tuesday, August 17, 2010

TYPES OF NETWORK

One way to categorize the different types of computer network designs is by their scope or scale. For historical reasons, the networking industry refers to nearly every type of design as some kind of area network. Common examples of area network types are:



LAN - Local Area Network


WLAN - Wireless Local Area Network


WAN - Wide Area Network


MAN - Metropolitan Area Network


SAN - Storage Area Network, System Area Network, Server Area Network, or sometimes Small Area Network


CAN - Campus Area Network, Controller Area Network, or sometimes Cluster Area Network


PAN - Personal Area Network


DAN - Desk Area Network


LAN and WAN were the original categories of area networks, while the others have gradually emerged over many years of technology evolution.
 
Personal Area Network (PAN)

The smallest type of network, a PAN simply involves connecting one person's computer to a number of devices or peripherals. Usually, all devices, such as printers, PDAs, and telephones, are within a few feet of the computer. A PAN can also refer to a connection to the internet.

Local Area Network (LAN)

If you have a home network with two or more computers or you are connected to other computers at your workplace, then you are on a LAN. LANs are ideal for networking in a small geographical area and can either work with cables and hubs, or wirelessly. They allow for the speedy transfer of data — up to 10Gbit/s. Most LANs are based on Ethernet technology. Wireless Local Area Networks are known as WLANs.

Campus Area Network (CAN)


CANs are so called because they are ideal for universities, but are also found in industrial facilities where networks in a number of buildings need to be connected. This is usually accomplished through bridging and routing. Again, most CANs are based on Ethernet technology.

Metropolitan Area Network (MAN)

A MAN usually consists of a number of interconnected LANs and WANs, but will not extend beyond the boundaries of a town, city, or metropolitan area. These are often operated at public utilities and are used by many businesses and individuals.

MAN technology has developed significantly in recent years with smaller networks within a MAN often interconnected wirelessly using radio, microwave or infra-red laser links.

Wide Area Network (WAN)

The WAN is the next step up from the MAN because it can cross metropolitan or even national boundaries. The best known WAN is the internet and, like all WANs, it uses routers and public communication links to carry data. While the internet is open to all, many WANs are run by private companies and are restricted.As the term implies, a WAN spans a large physical distance. The Internet is the largest WAN, spanning the Earth.


A WAN is a geographically-dispersed collection of LANs. A network device called a router connects LANs to a WAN.


Storage Area Network

 connects servers to data storage devices through a technology like Fibre Channel.

Wednesday, August 04, 2010

COMPUTER NETWORKS


Network means Interconnection. A computer Network is interconnection between two or more autonomous computers or computer like devices.
                   OR 
computer network, often simply referred to as a network, is a collection of computers and devices connected by communications channels that facilitates sharing of resources like information, hardware,files, etc.


PURPOSE



Computer networks can be used for several purposes:
  • Facilitating communications. Using a network, people can communicate efficiently and easily via e-mail, instant messaging, chat rooms, telephone, video telephone calls, and video conferencing.
  • Sharing hardware. In a networked environment, each computer on a network can access and use hardware on the network. Suppose several personal computers on a network each require the use of a laser printer. If the personal computers and a laser printer are connected to a network, each user can then access the laser printer on the network, as they need it.
  • Sharing files, data, and information. In a network environment, any authorized user can access data and information stored on other computers on the network. The capability of providing access to data and information on shared storage devices is an important feature of many networks.
  • Sharing software. Users connected to a network can access application programs on the network.



A computer network is a system in which computers are connected to share information and resources. The connection can be done as peer-to-peer or client/server.

WELCOME AGAIN in NEW AAVTAR

Hi Friends
               This is the  time I start blogging again. You can say the NEW AAVTAR. As previous the blogging based on Computer Science, Information Technology, related topics and many more. Beside blogging i also provide you some important and useful widgets. I think you can benefited from these. This time i also think to complete the work which is pending from last one and half years. Yes you think right the committed website for you. Next in next Post. ENJOY...