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Tuesday, 29 May 2012

What is Internet?

What is internet?

The internet in simple terms is a network of the interlinked computer networking worldwide, which is accessible to the general public. These interconnected computers work by transmitting data through a special type of packet switching which is known as the IP or the internet protocol.

Internet is such a huge network of several different interlinked networks relating to the business, government, academic, and even smaller domestic networks, therefore internet is known as the network of all the other networks. These networks enable the internet to be used for various important functions which include the several means of communications like the file transfer, the online chat and even the sharing of the documents and web sites on the WWW, or the World Wide Web.

The use of IP in the Internet is the integral part of the network, as they provide the services of the internet, through different layers organization through the IP data packets. There are other protocols that are the sub-classes of the IP itself, like the TCP, and the HTTP.

Internet infrastructures :

Internet Protocol (IP) :

-  The Internet Protocol (IP) is the principal communications protocol used for relaying datagrams (also known as network packets) across an internetwork using the Internet Protocol Suite. Responsible for routing packets across network boundaries, it is the primary protocol that establishes the Internet.

IP is the primary protocol in the Internet Layer of the Internet Protocol Suite and has the task of delivering datagrams from the source host to the destination host solely based on the addresses. For this purpose, IP defines datagram structures that encapsulate the data to be delivered. It also defines addressing methods that are used to label the datagram source and destination.

Historically, IP was the connectionless datagram service in the original Transmission Control Program introduced by Vint Cerf and Bob Kahn in 1974, the other being the connection-oriented Transmission Control Protocol (TCP). The Internet Protocol Suite is therefore often referred to as TCP/IP.

Function of IP :

- The Internet Protocol is responsible for addressing hosts and routing datagrams (packets) from a source host to the destination host across one or more IP networks. For this purpose the Internet Protocol defines an addressing system that has two functions: identifying hosts and providing a logical location service. This is accomplished by defining standard datagrams and a standard addressing system.

Each datagram has two components, a header and a payload. The IP header is tagged with the source IP address, destination IP address, and other meta-data needed to route and deliver the datagram. The payload is the data to be transported. This process of nesting data payloads in a packet with a header is called encapsulation.

Perhaps the most complex aspects of IP are IP addressing and routing. Addressing refers to how end hosts are assigned IP addresses and how subnetworks of IP host addresses are divided and grouped. IP routing is performed by all hosts, but most importantly by routers, which typically use either interior gateway protocols (IGPs) or external gateway protocols (EGPs) to decide how to move datagrams among networks.

IP routing is also common in local networks. For example, Ethernet switches sold today support IP multicast.  These switches use IP addresses and Internet Group Management Protocol for control of the multicast routing but use MAC addresses for the actual routing.

Wireless Technology

What is Wireless Computer Networking?

Wireless networks utilize radio waves and/or microwaves to maintain communication channels between computers. Wireless networking is a more modern alternative to wired networking that relies on copper and/or fiber optic cabling between network devices.
A wireless network offers advantages and disadvantages compared to a wired network. Advantages of wireless include mobility and elimination of unsightly cables. Disadvantages of wireless include the potential for radio interference due to weather, other wireless devices, or obstructions like walls.
Wireless is rapidly gaining in popularity for both home and business networking. Wireless technology continues to improve, and the cost of wireless products continues to decrease. Popular wireless local area networking (WLAN) products conform to the 802.11 "Wi-Fi" standards. The gear a person needs to build wireless networks includes network adapters (NICs), access points (APs), and routers.

Devices commonly used wireless technology :

1) Portable computers.
2) Desktop computers.
3) PDAs.
4) Cellulars phones.
5) GPS.

Types of wireless :

A wireless network joins two or more than two computers by means of communication without using any wires. Wireless Networks utilizes spread-spectrum or OFDM depends on the technology which is using .Wireless network enable a user to move about within a wide coverage area and still be associated to the network. There are different types of wireless networking such as wide area network, local area network and personal area network but the most common are of two.

WLAN (Wireless Local Area Network)
WLANs provide wireless network contact using radio signal instead of traditional network cabling and built by joining a device called AP through which a user converse with the AP using a wireless network. WLAN also network security because it relics an important issue for WLANs. The WEP technology used in WLAN elevate the rank of security. WLANs have expanded well-built status in a different kind of markets during the last seven years and set up to offer wireless connectivity within a limited exposure area which may be a hospital, a university, the airport, health care providers or a gas plant. WLAN is providing highest data-transfer rate with 802.11 terminologies. Today WLANs are fetching more usually recognized as a general-purpose connectivity substitute for a wide array of business customers. WLANs offering various benefit for user such as mobility, condensed Cost-of-Ownership, installation speed and flexibility and scalability. The technology used in WLANs is Spread Spectrum developed by the military offer secure and reliable services. Frequency-hopping spread-spectrum maintains a single logical channel and Direct-Sequence Spread Spectrum offer chip pattern to make it more effective and infrared technology. Wireless LAN adapters are necessary for regular computer platforms. The benefits of WLAN  are high Range and coverage, Throughput, Mulitpath Effects, Integrity, Interoperability with Wired Infrastructure, Interoperability with Wireless Infrastructure, Interference and Coexistence, Simplicity and Ease of Use, Security, Cost, Scalability and , Safety which makes a wireless network in real a great platform.

WMAN (Wireless Metropolitan Area Network)
Fast communications of network within the vicinity of a metropolitan area is called WMAN, that put up an entire city or other related geographic area and can span up to 50km. WMAN designed for a larger geographical area than a LAN. The standard of MAN is DQDB which cover up to 30 miles with the speed of 34 Mbit/s to 155 Mbit/s.1t is more common in schools, colleges, and public services support a high-speed network backbone. WMAN is a certified name by the IEEE 802.16 that functioning on Broadband for its wireless metropolitan. WMAN have air interface and a single-carrier scheme intended to activate in the 10-66 GHz spectrum, supports incessantly unreliable transfer levels at many certified frequencies. WMAN opens the door for the creation and Provide high-speed Internet access to business subscribers.It can handle thousands of user stations with prevents collisions and support legacy voice systems, voice over IP, TCP/IP. WMAN offer different applications with different QoS requirements.The technology of WMAN consist of ATM, FDDI, and SMDS. WiMAX is a term used for Wireless metropolitan area network and plinth on the IEEE 802.16.

Protocol and Cabling

A protocol is a set of rules that governs the communications between computers on a network. In order for two computers to talk to each other, they must be speaking the same language. Many different types of network protocols and standards are required to ensure that your computer (no matter which operating system, network card, or application you are using) can communicate with another computer located on the next desk or half-way around the world. The OSI (Open Systems Interconnection) Reference Model defines seven layers of networking protocols. The complexity of these layers is beyond the scope of this tutorial; however, they can be simplified into four layers to help identify some of the protocols with which you should be familiar.

OSI Layer
Common Protocols
HTTP | FTP | SMTP | DNS | Telnet
Data Link
           OSI model related to common network protocols

The original Ethernet standard was developed in 1983 and had a maximum speed of 10 Mbps (phenomenal at the time) over coaxial cable. The Ethernet protocol allows for bus, star, or tree topologies, depending on the type of cables used and other factors. This heavy coaxial cabling was expensive to purchase, install, and maintain, and very difficult to retrofit into existing facilities.
The current standards are now built around the use of twisted pair wire. Common twisted pair standards are 10BaseT, 100BaseT, and 1000BaseT. The number (10, 100, 1000) ands for the speed of transmission (10/100/1000 megabits per second); the "Base" stands for "baseband" meaning it has full control of the wire on a single frequency; and the "T" stands for "twisted pair" cable. Fiber cable can also be used at this level in 10BaseFL.

Fast Ethernet
The Fast Ethernet protocol supports transmission up to 100 Mbps. Fast Ethernet requires the use of different, more expensive network concentrators/hubs and network interface cards. In addition, category 5 twisted pair or fiber optic cable is necessary. Fast Ethernet standards include:
  • 100BaseT - 100 Mbps over 2-pair category 5 or better UTP cable.
  • 100BaseFX - 100 Mbps over fiber cable.
  • 100BaseSX -100 Mbps over multimode fiber cable.
  • 100BaseBX - 100 Mbps over single mode fiber cable.
Ethernet Protocol Summary

Twisted Pair, Coaxial, Fiber
10 Mbps
Fast Ethernet
Twisted Pair, Fiber
100 Mbps
Gigabit Ethernet
Twisted Pair, Fiber
1000 Mbps

What is Network Cabling?
Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs. In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. Understanding the characteristics of different types of cable and how they relate to other aspects of a network is necessary for the development of a successful network.
  • Unshielded Twisted Pair (UTP) Cable
  • Shielded Twisted Pair (STP) Cable
  • Coaxial Cable
  • Fiber Optic Cable
  • Cable Installation Guides
  • Wireless LANs
  • Unshielded Twisted Pair (UTP) Cable
Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks.

The quality of UTP may vary from telephone-grade wire to extremely high-speed cable. The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices. The tighter the twisting, the higher the supported transmission rate and the greater the cost per foot. The EIA/TIA (Electronic Industry Association/Telecommunication Industry Association) has established standards of UTP and rated six categories of wire (additional categories are emerging).

When running cable, it is best to follow a few simple rules:
  • Always use more cable than you need. Leave plenty of slack.
  • Test every part of a network as you install it. Even if it is brand new, it may have problems that will be difficult to isolate later.
  • Stay at least 3 feet away from fluorescent light boxes and other sources of electrical interference.
  • If it is necessary to run cable across the floor, cover the cable with cable protectors.
  • Label both ends of each cable.
  • Use cable ties (not tape) to keep cables in the same location together.
Advantages of wireless networks:
  • Mobility - With a laptop computer or mobile device, access can be available throughout a school, at the mall, on an airplane, etc. More and more businesses are also offering free WiFi access ("Hot spots").
  • Fast setup - If your computer has a wireless adapter, locating a wireless network can be as simple as clicking "Connect to a Network" -- in some cases, you will connect automatically to networks within range.
  • Cost - Setting up a wireless network can be much more cost effective than buying and installing cables.
  • Expandability - Adding new computers to a wireless network is as easy as turning the computer on (as long as you do not exceed the maximum number of devices).
Disadvantages of wireless networks:
  • Security - Be careful. Be vigilant. Protect your sensitive data with backups, isolated private networks, strong encryption and passwords, and monitor network access traffic to and from your wireless network.
  • Interference - Because wireless networks use radio signals and similar techniques for transmission, they are susceptible to interference from lights and electronic devices.
  • Inconsistent connections - How many times have you hears "Wait a minute, I just lost my connection?" Because of the interference caused by electrical devices and/or items blocking the path of transmission, wireless connections are not nearly as stable as those through a dedicated cable.
  • Speed - The transmission speed of wireless networks is improving; however, faster options (such as gigabit Ethernet) are available via cables. If you are only using wireless for internet access, the actual internet connection for your home or school is generally slower than the wireless network devices, so that connection is the bottleneck. If you are also moving large amounts of data around a private network, a cabled connection will enable that work to proceed much faster.

Networking Hardware

I'm gonna tell you about network hardware. I will be focused on five networking hardware that is RepeatersHubsBridgesSwitches and Routers.


- Repeaters are simple two-port signal amplifiers. They are used in a bus topology to extend the maximum distance that can be spanned on a cable run. The strength of the signal is boosted as it travels down the wire. A repeater will receive a digital signal on one of its ports, amplify it, and transmit it out the other side. A repeater is like a typical home stereo amplifier. The amp takes the signal it receives from the CD, tape deck, etc., and amplifies the signal and sends it on its way to the speakers. If the signal is a brand new Alanis Morisett CD, it simply boosts the signal and sends it on its way. If it's an old Grateful Dead concert tape that is inaudible from the amount of background hiss, it happily boosts this signal as well and sends it on its way. Repeaters function similar to stereo amplifiers. They simply boost whatever they receive and send it on its way. Unfortunately the signal they receive could be a good frame of data, a bad frame of data, or even background noise. A repeater does not discern data quality; it simply looks at each of the individual digital pulses and amplifies them.

Repeaters access point


Hubs are probably the most common piece of network hardware after network interface cards. Physically, they are boxes of varying sizes that have multiple female RJ-45 connectors. Each connector is designed to accept one twisted-pair cable outfitted with a male RJ-45 connector. This twisted-pair cable is then used to connect a single server or workstation to the hub. Hubs are essentially multi-port repeaters that support twisted-pair cables in a star typology. Each node communicates with the hub, which in turn amplifies the signal and transmits it on its remaining ports. As with a repeater, hubs work at the electrical level. Because hubs have no way to determine if a frame is good or bad, they should be looked at, when you design your network typology, as functionally identical to repeaters.

Various types of hubs


 Bridge looks a lot like a repeater; it is a small box with two network connectors that attach to two separate portions of the network. A bridge incorporates the functionality of a repeater (signal amplification), but it actually looks at the frames of data, which is a great benefit. A common bridge is nearly identical to a repeater except for the indicator lights, as shown in figure below. A forward light flashes whenever the bridge needs to pass traffic from one collision domain to another.


Bridges networking


Switches are the marriage of hub and bridge technology. They resemble stackable hubs in appearance, having multiple RJ-45 connectors for connecting network systems. Instead of being a dumb amplifier like a hub, however, switches function as though they have a little miniature bridge built into each port. A switch will keep track of the MAC addresses attached to each of its ports and direct traffic destined for a certain address only to the port to which it is attached.

Network switch


A router is a multi-port device that makes decisions on how to handle a frame, based on protocol and network address. To truly understand what this means we must first look at what a protocol is and how it works. Up until now we've been happily communicating using the media access control address assigned to our networking devices. Our systems have used this number to contact other systems and transmit information as required.

How routers work.