?? What is Hardware 

Hardware is the physical, tangible components of a computer or other electronic device. The term hardware traditionally refers to the physical components of any technology, which is paired with human or animal power and skill to perform it's function.Computer hardware is usually paired with software to perform it's function, and the two together are referred to as a computer system. The first hardware considered to be useful for computations was the tally stick, in use from about 35,000 BC until the mid 20th century. The first hardware that received instructions from software was probably the Jacquard loom in the early 19th century.

Personal computer hardware consists of all electronic parts, with the exception of the enclosure case. Hardware found in all desktop and laptop personal computers include the motherboard, at least one processor, memory, storage, an output device such as a monitor, and at least one input device such as a keyboard or mouse. All cables, connectors, fans, and other tangible components are considered hardware as well. Although most desktop computers can be readily disassembled into the individual hardware components, many laptops have two or more components assembled in a way that makes separation difficult or impossible. Laptop processors, for example, are often soldered onto the motherboard.

Embedded systems and other electronic devices may use specialized hardware that is not compatible with other similar systems, alternatively they may use generic, standardized hardware. Portable media players such as the iPod usually have proprietary casings, screens, and circuitry. However, the storage facilities of most portable media players are standard flash memory or hard drives that can be exchanged between models. The hardware inside a wristwatch will almost always be proprietary, however many watches use the same batteries and standardized fittings for the wristband. Automobile computers often use almost identical cases and internal circuitry within each manufacturer, however the onboard software and wiring harness is different across models.

What is Linux ?

 ???What is Linux

Linux is an open source operating system. Although traditionally 

used on servers, Linux has recently been gaining acceptance on home desktop computers. Linux is often perceived as an 'alternative' operating system to Microsoft Windows or Apple OS-X due to its non-commercial nature. Linux is developed by a team of thousands of volunteers worldwide, and most distributions are freely distributed.

The name "Linux" technically refers only to the kernel of the operating system. Distributors take this kernel and add their own packages and programs to it, then distribute it as a distro. However, popular use refers to any Linux distro simply as "Linux", just as Windows XP and Windows 98 are both referred to simply as "Windows". It is the popular definition, and not the technical definition, that you will see referred to on this website.

Linux logo

Popular Linux distros include Red Hat, Fedora, SUSE, Debian, Ubuntu, Slackware, Gentoo, and Mandriva. There are literally thousands more. Note that Linux's GPL licence makes the forking of a distro possible- that is why Red Hat and Fedora are usually associated with one another. The same company distributes both of them, however to different users for different purposes. Another similar situation is seen between Debian and Ubuntu. Ubuntu is a Debian fork. That means that Ubuntu's developers adopt a stable Debian release and modify it to create Ubuntu. This practice is legal and encouraged in Linux circles.

 ?? What is an Operating System

An operating system is the lowest-level program running on a computer. The operating system provides software interfaces for the computer hardware, basic input and output functions, file and network management, and memory allocation. On top of these functions the user may run a command line, web, or graphical user interface. Additionally, the operating systems of non-specialized home and office computers are able to run third-party programs that either extend the functionality of the computer, or provide alternative interfaces to the existing functions. These programs need not know what hardware the computer consists of: the operating system provides the hardware abstraction necessary for running a single program on millions of different possible hardware combinations.

Most home computers today use the Microsoft Windows operating system. Other operating systems, such as Apple Macintosh and Linux, have traditionally been termed as "alternative operating systems", implying that Windows is usually expected to be installed by default. However, the usability issues surrounding Windows Vista, combined with improvements in the usability of graphical user interfaces for Linux, have catalyzed renewed interest in Linux and Macintosh. Other concerns, such as restrictive licensing and DRM issues, are expected to further interest in alternative, mostly open source operating systems. Currently, Linux is the leading open source operating system, with many distributions consisting entirely of open source software.

an Operating System logo

The first computers had no operating systems. The hardware of these early systems was very specialized, and only certain types of programs would run on them. These programs, being so specialized, interfaced directly with the system's hardware. Thus, these programs were not portable and any changes in hardware required changes in the computer program. As computers became less specialized, and different companies began producing hardware, the need for abstraction layers that would allow programs to run on the various hardware became apparent. Hence the concept of the shared library was invented, the first of which provided uniform software interfaces to various hardware. Later, these libraries incorporated time-sharing management tools and automatic job switching functions. Thus, the operating system was born.

                 ?? What is a Protocol 

A protocol is a system of rules that define how something is to be done. In computer terminology, a protocol is usually an agreed-upon or standardized method for transmitting data and/or establishing communications between different devices. Just as two humans need to have a common language between them before they can begin to share ideas and information, so must computers have a common way of sending information between them. The Internet is often used as an example of a successful protocols-based system in which the implementation of key qualities of protocols, such as error correction and message formatting, are utilized and respected across a wide variety of hardware and software.

To demonstrate a common usage of a popular protocol, we can examine the Internet's TCP/IP protocol. Computers can communicate different types of information over TCP/IP such as text, pictures, VOIP (Voice Over Internet Protocol), and more. To indicate that a user wants the page "protocol.html" from the What-Is-What website, the web browser Firefox connects to the What-Is-What server and sends this information: "GET /what_is/protocol.html HTTP/1.1". The server knows that the request is divided into three sections by spaces, and knows what values to expect in each section. The first section specifies the type of request, in this case a GET request. The next section is the location request, in this case the file "protocol.html" which is located in the "what_is" directory. The final section is the transport protocol that the browser would like to use, in this case version 1.1 of HTTP (HyperText Transfer Protocol). If Firefox were to request these properties in a different order, say, with the GET section at the end instead of at the beginning, the web server would not be able to understand the request. The order, and type, of the request is defined in the TCP/IP suite of protocols.

a Protocol logo

In the previous example, we saw how one protocol, TCP/IP, was used to specify the use of another protocol, HTTP. This is an example of high- and low-level protocols and how they interact. TCP and IP are low-level protocols, that are used in establishing the basic connection between two computers on a network. However, just simply connecting does nothing practical, and information must actually be transferred. Just like the low-level protocol defines the properties of the connection, a high-level protocol (such as HTTP) defines the properties of the data transfer. In addition to the familiar HTTP protocol, other common Internet protocols include FTP (File Transfer Protocol), DHCP (Dynamic Host Configuration Protocol), SMTP (Simple Mail Transfer Protocol), POP3 (Post Office Protocol version 3), and IMAP (Internet Message Access Protocol). You have probably noticed that all these acronyms end in the letter "P". In fact, whenever encountered with an unfamiliar computer-related acronym that ends in "P", there is a very good chance that it defines a protocol.

?? What is the World Wide Web 

The World Wide Web is a network of computers that serve webpages. The World Wide Web is a major component of the Internet, along with email, Usenet, ftp, and some other minor protocols. The term "world wide" refers to the global nature of the World Wide Web, and the term "web" refers to the interlinking of documents by means of hypertext. In simple terms, this means that documents on the Web (or WWW for short) can reference, or link to, other documents by simply stating on which machine they reside, and where on that machine. Computers that serve documents on the World Wide Web are called servers, and the programs used to connect to servers and to display webpages are called web browsers.

Documents on the World Wide Web are traditionally written in HTML, a major component of the web. HTML defines the appearance and content of a webpage, and usually links to other HTML pages via a Uniform Resource Identifier or Uniform Resource Locator (URL). The pages are transferred between computers via HTTP, the HyperText Transfer Protocol. The most familiar of these concepts is without doubt the URL, such as "http://what-is-what.com/what_is/world_wide_web.html". The first part: "http://" means that the document should be fetched using the HTTP protocol. The next part, "what-is-what.com/" is the name of the server on which the document resides. The last part: "what_is/world_wide_web.html" means that the document named "world_wide_web.html" resides in the "what_is" folder. Note the suffix ".html". Usually, file name extensions indicate in what format the file was written. In this case, the file is written in HTML. This is expected, as the file is meant to be accessed on the WWW.

the World Wide Web logo

The history of the The World Wide Web dates back to 1980. In that year Tim Berners-Lee, a physicist at CERN (the European Organization for Nuclear Research), devised a way for moving documents between remote computers. The proprietary system, named ENQUIRE, went through several monumental changes between 1980 and its public release in 1991. The physicists at CERN were in need of a simple way for non-computer literate scientists to exchange data between laboratories very far apart. Thus, a simple to learn language for creating documents in outline format was invented, called HTML. In order to transfer the documents between computers, a simple text-based protocol was needed, thus HTTP was invented. The computers that understood HTTP requests and served HTML documents in response were called servers, and the programs used to actually view the documents were called browsers. As the system of requesting and viewing documents could be used by a computer anywhere in the world by any compliant computer connected to a phone line, the system was called the World Wide Web.

What is Go-oo?

 ??What is Go-oo

Go-oo is a community-developed fork of Sun's Open Office office suit. Go-oo contains features and improvements that for technical or legal reasons cannot be included in Sun's version of Open Office. Most Linux distributions today use Go-oo instead of the standard Open Office packages, however, the splash screen and "About" dialogs usually remain the standard Open Office versions. This is at Sun's request, to enhance brand recognition and is in stark contrast to Mozilla's stance on Firefox forks, notably Iceweasel.

Although Open Office is open source, Sun does not accept contributions from outside Sun unless the developer gives Sun ownership of the contributed code. This ownership means that Sun can release this code under what ever license Sun chooses. Most code is released twice: once in OOo (Open Office) under the GPL license, and once again in Star Office under a proprietary Sun license. Star Office, Sun's commercial office suit, is built from much of the same code base as OOo, however being a proprietary application it cannot incorporate GPL code.

Go-oo logo

Community frustration regarding Sun's licensing requirements and refusal to add critical features catalyzed several forks of Open Office, which is explicitly permitted under the GPL license. Go-oo is the leading OOo fork for Linux, incorporating enhanced compatibility with competing office suits, snappier performance, and additional features. Compatibility with other office suites is provided by filters capable of parsing Microsoft Office's native OOXML format, MS Works, and Lotus Word Pro files. Snappier performance is seen is faster startup times and improved code profiling. Some of the more useful features in Go-oo that are missing from OOo include SVG support, VBA macro support, 3D transition effects, and a built-in multimedia framework.

What is an IP Address?

Internet Protocol Address (or IP Address) is an unique address that computing devices such as personal computers, tablets, and smartphones use to identify itself and communicate with other devices in the IP network. Any device connected to the IP network must have an unique IP address within the network. An IP address is analogous to a street address or telephone number in that it is used to uniquely identify an entity.

Dotted Decimals

The traditional IP Addresses (known as IPv4) uses a 32-bit number to represent an IP address, and it defines both network and host address. A 32-bit number is capable of providing roughly 4 billion unique numbers, and hence IPv4 addresses running out as more devices are connected to the IP network. A new version of the IP protocol (IPv6) has been invented to offer virtually limitless number of unique addresses. An IP address is written in "dotted decimal" notation, which is 4 sets of numbers separated by period each set representing 8-bit number ranging from (0-255). An example of IPv4 address is 216.3.128.12, which is the IP address previously assigned to iplocation.net.

An IPv4 address is divided into two parts: network and host address. The network address determines how many of the 32 bits are used for the network address, and remaining bits for the host address. The host address can further divided into subnetwork and host number.

Class A, B, C and CIDR networks

Traditionally IP network is classified as A, B or C network. The computers identified the class by the first 3 bits (A=000, B=100, C=110), while humans identify the class by first octet(8-bit) number. With scarcity of IP addresses, the class-based system has been replaced by Classless Inter-Domain Routing (CIDR) to more efficiently allocate IP addresses.

Class	Network Address	Number of Hosts	Netmask
CIDR	/4	240,435,456	240.0.0.0
CIDR	/5	134,217,728	248.0.0.0
CIDR	/6	67,108,864	252.0.0.0
CIDR	/7	33,554,432	254.0.0.0
A	/8 (1-126)	16,777,216	255.0.0.0
CIDR	/9	8,388,608	255.128.0.0
CIDR	/10	4,194,304	255.192.0.0
CIDR	/11	2,097,152	255.224.0.0
CIDR	/12	1,048,576	255.240.0.0
CIDR	/13	524,288	255.248.0.0
CIDR	/14	262,144	255.252.0.0
CIDR	/15	131,072	255.254.0.0
B	/16 (128-191)	65,534	255.255.0.0
CIDR	/17	32,768	255.255.128.0
CIDR	/18	16,384	255.255.192.0
CIDR	/19	8,192	255.255.224.0
CIDR	/20	4,096	255.255.240.0
CIDR	/21	2,048	255.255.248.0
CIDR	/22	1,024	255.255.252.0
CIDR	/23	512	255.255.254.0
C	/24 (192-223)	256	255.255.255.0
CIDR	/25	128	255.255.255.128
CIDR	/26	64	255.255.255.192
CIDR	/27	32	255.255.255.224
CIDR	/28	16	255.255.255.240
CIDR	/29	8	255.255.255.248
CIDR	/30	4	255.255.255.252

Note: (1) 127 Network Address reserved for loopback test. (2) Class D (224-247, Multicast) and Class E (248-255, Experimental) are not intended to be used in public operation. 

Public and Private IP Addresses 

In order to maintain uniqueness within global namespace, the IP addresses are publicly registered with the Network Information Center (NIC) to avoid address conflicts. Devices that need to be publicly identified such as web or mail servers must have a globally unique IP address, and they are assigned a public IP address. Devices that do not require public access may be assigned a private IP address, and make it uniquely identifiable within one organization. For example, a network printer may be assigned a private IP address to prevent the world from printing from it. To allow organizations to freely assign private IP addresses, the NIC has reserved certain address blocks for private use. A private network is a network that uses RFC 1918 IP address space. The following IP blocks are reserved for private IP addresses.

Class	Starting IP Address	Ending IP Address
A	10.0.0.0	10.255.255.255
B	172.16.0.0	172.31.255.255
C	192.168.0.0	192.168.255.255

In addition to above classful private addresses, 169.254.0.0 through 169.254.255.255 addresses are reserved for Zeroconf (or APIPA, Automatic Private IP Addressing) to automatically create the usable IP network without configuration.

What is loopback IP address? 

The loopback IP address is the address used to access itself. The IPv4 designated 127.0.0.1 as the loopback address with the 255.0.0.0 subnet mask. A loopback interface is also known as a virtual IP, which does not associate with hardware interface. On Linux systems, the loopback interface is commonly called lo or lo0. The corresponding hostname for this interface is called localhost.

The loopback address is used to test network software without physically installing a Network InterfaceCard (NIC), and without having to physically connect the machine to a TCP/IP network. A good example of this is to access the web server running on itself by using http://127.0.0.1 or http://localhost.

What is a Hybrid Vehicle?

 ??What is a Hybrid Vehicle

A hybrid car is an automobile that has two or more major sources of propulsion power. Most hybrid cars currently marketed to consumers have both conventional gasoline and electric motors, with the ability to power the vehicle by either one independently or in tandem. These vehicles are appropriately termed gas-electric hybrids. Other power sources may include hydrogen, propane, CNG, and solar energy. The technology used depends on the goals set for the vehicle, whether they be fuel efficiency, power, driving range, or reduced greenhouse gas emissions. Consumer oriented hybrid cars, which have been on the market for about ten years, are usually tuned for reduced emissions and driving range. Additionally, owners of hybird vehicles often enjoy social benefits such as prestige and discounted secondary services. Some Chicago hotels as well as hotels in other cities give parking discounts to people driving hybrid cars. Corporate and government fleets that have been in service for twenty years or more are usually tuned for fuel efficiency, often at the cost of driving range, power, and hydrocarbon emissions.

A gasoline-electric hybrid car has one or two auxiliary electric motors that supplement the main gasoline engine. Compared to conventional automobiles, the gasoline engine in a gas-electric hybrid is smaller, less powerful, and more efficient. Although the gasoline engine alone would be sufficient to power the vehicle under most circumstances, during maneuvers requiring unusually high power the electric motor is used as well. These conditions include passing, hill climbing, and acceleration from a standstill. Some hybrid cars, such as the Toyota Prius, shut down the gasoline engine under conditions in which the electric motor alone would suffice, such as coasting and breaking. In fact, the Toyota Prius has a special electric-only mode designed for stop-and-go traffic. This is made possible by the super heavy duty electric motor used in the Prius, which is capable of propelling the vehicle from a standstill without the gasoline assist. Thus, in contrast to most other hybrid vehicles, the Prius actually uses the electric motor more than the gasoline engine.

a Hybrid Vehicle logo

Many of the technologies found in hybrid vehicles would benefit vehicles of any type, including conventional gasoline automobiles. However, the engineering and manufacturing costs associated with these technologies often would increase the price of the vehicle to the point where the fuel savings are negligible in comparison. Only in tax-subsidized electric and hybrid vehicles are these technologies practical, in which associated cost increases are absorbed by the government instead of the manufacturer or consumer. These technologies include regenerative braking, aerodynamic refinements, and lightweight building materials.

What is a Subnet Mask?

An IP address has two components, the network address and the host address. A subnet mask separates the IP address into the network and host addresses (<network><host>). Subnetting further divides the host part of an IP address into a subnet and host address (<network><subnet><host>) if additional subnetwork is needed. Use the Subnet Calculator to retrieve subnetwork information from IP address and Subnet Mask. It is called a subnet mask because it is used to identify network address of an IP address by perfoming a bitwise AND operation on the netmask.

A Subnet mask is a 32-bit number that masks an IP address, and divides the IP address into network address and host address. Subnet Mask is made by setting network bits to all "1"s and setting host bits to all "0"s. Within a given network, two host addresses are reserved for special purpose, and cannot be assigned to hosts. The "0" address is assigned a network address and "255" is assigned to a broadcast address, and they cannot be assigned to hosts.

Examples of commonly used netmasks for classed networks are 8-bits (Class A), 16-bits (Class B) and 24-bits (Class C), and classless networks are as follows:

Class	Address	# of Hosts	Netmask (Binary)	Netmask (Decimal)
CIDR	/4	240,435,456	11110000 00000000 00000000 00000000	240.0.0.0
CIDR	/5	134,217,728	11111000 00000000 00000000 00000000	248.0.0.0
CIDR	/6	67,108,864	11111100 00000000 00000000 00000000	252.0.0.0
CIDR	/7	33,554,432	11111110 00000000 00000000 00000000	254.0.0.0
A	/8	16,777,216	11111111 00000000 00000000 00000000	255.0.0.0
CIDR	/9	8,388,608	11111111 10000000 00000000 00000000	255.128.0.0
CIDR	/10	4,194,304	11111111 11000000 00000000 00000000	255.192.0.0
CIDR	/11	2,097,152	11111111 11100000 00000000 00000000	255.224.0.0
CIDR	/12	1,048,576	11111111 11110000 00000000 00000000	255.240.0.0
CIDR	/13	524,288	11111111 11111000 00000000 00000000	255.248.0.0
CIDR	/14	262,144	11111111 11111100 00000000 00000000	255.252.0.0
CIDR	/15	131,072	11111111 11111110 00000000 00000000	255.254.0.0
B	/16	65,534	11111111 11111111 00000000 00000000	255.255.0.0
CIDR	/17	32,768	11111111 11111111 10000000 00000000	255.255.128.0
CIDR	/18	16,384	11111111 11111111 11000000 00000000	255.255.192.0
CIDR	/19	8,192	11111111 11111111 11100000 00000000	255.255.224.0
CIDR	/20	4,096	11111111 11111111 11110000 00000000	255.255.240.0
CIDR	/21	2,048	11111111 11111111 11111000 00000000	255.255.248.0
CIDR	/22	1,024	11111111 11111111 11111100 00000000	255.255.252.0
CIDR	/23	512	11111111 11111111 11111110 00000000	255.255.254.0
C	/24	256	11111111 11111111 11111111 00000000	255.255.255.0
CIDR	/25	128	11111111 11111111 11111111 10000000	255.255.255.128
CIDR	/26	64	11111111 11111111 11111111 11000000	255.255.255.192
CIDR	/27	32	11111111 11111111 11111111 11100000	255.255.255.224
CIDR	/28	16	11111111 11111111 11111111 11110000	255.255.255.240
CIDR	/29	8	11111111 11111111 11111111 11111000	255.255.255.248
CIDR	/30	4	11111111 11111111 11111111 11111100	255.255.255.252

Subnetting an IP network is to separate a big network into smaller multiple networks for reorganization and security purposes. All nodes (hosts) in a subnetwork see all packets transmitted by any node in a network. Performance of a network is adversely affected under heavy traffic load due to collisions and retransmissions.

Applying a subnet mask to an IP address separates network address from host address. The network bits are represented by the 1's in the mask, and the host bits are represented by 0's. Performing a bitwise logical AND operation on the IP address with the subnet mask produces the network address. For example, applying the Class C subnet mask to our IP address 216.3.128.12 produces the following network address:

IP:   1101 1000 . 0000 0011 . 1000 0000 . 0000 1100  (216.003.128.012)
Mask: 1111 1111 . 1111 1111 . 1111 1111 . 0000 0000  (255.255.255.000)

      1101 1000 . 0000 0011 . 1000 0000 . 0000 0000  (216.003.128.000)

      ---------------------------------------------

Subnetting Network 

Here is another scenario where subnetting is needed. Pretend that a web host with a Class C network needs to divide the network so that parts of the network can be leased to its customers. Let's assume that a host has a network address of 216.3.128.0 (as shown in the example above). Let's say that we're going to divide the network into 2 and dedicate the first half to itself, and the other half to its customers.

   216 .   3 . 128 . (0000 0000)  (1st half assigned to the web host)

   216 .   3 . 128 . (1000 0000)  (2nd half assigned to the customers)

The web host will have the subnet mask of 216.3.128.128 (/25). Now, we'll further divide the 2nd half into eight block of 16 IP addresses.

   216 .   3 . 128 . (1000 0000)  Customer 1 -- Gets 16 IPs (14 usable)
   216 .   3 . 128 . (1001 0000)  Customer 2 -- Gets 16 IPs (14 usable)

   216 .   3 . 128 . (1011 0000)  Customer 4 -- Gets 16 IPs (14 usable)
216 .   3 . 128 . (1010 0000)  Customer 3 -- Gets 16 IPs (14 usable)
   216 .   3 . 128 . (1100 0000)  Customer 5 -- Gets 16 IPs (14 usable)

   216 .   3 . 128 . (1111 0000)  Customer 8 -- Gets 16 IPs (14 usable)
216 .   3 . 128 . (1101 0000)  Customer 6 -- Gets 16 IPs (14 usable)
   216 .   3 . 128 . (1110 0000)  Customer 7 -- Gets 16 IPs (14 usable)
   -----------------------------

   255 . 255 . 255 . (1111 0000)  (Subnet mask of 255.255.255.240)

You may use Subnet Calculator to ease your calculation.

CIDR - Classless Inter Domain Routing 

Classless InterDomain Routing (CIDR) was invented to keep the Internet from running out of IP Addresses. The IPv4, a 32-bit, addresses have a limit of 4,294,967,296 (2³²) unique IP addresses. The classful address scheme (Class A, B and C) of allocating IP addresses in 8-bit increments can be very wasteful. With classful addressing scheme, a minimum number of IP addresses allocated to an organization is 256 (Class C). Giving 256 IP addresses to an organization only requiring 15 IP addresses is wasteful. Also, an organization requiring more than 256 IP addresses (let's say 1,000 IP addresses) is assigned a Class B, which allocates 65,536 IP addresses. Similarly, an organization requiring more than 65,636 (65,634 usable IPs) is assigned a Class A network, which allocates 16,777,216 (16.7 Million) IP addresses. This type of address allocation is very wasteful.

With CIDR, a network of IP addresses is allocated in 1-bit increments as opposed to 8-bits in classful network. The use of a CIDR notated address can easily represent classful addresses (Class A = /8, Class B = /16, and Class C = /24). The number next to the slash (i.e. /8) represents the number of bits assigned to the network address. The example shown above can be illustrated with CIDR as follows:

   216.3.128.12, with subnet mask of 255.255.255.128 is written as
   216.3.128.12/25


   Similarly, the 8 customers with the block of 16 IP addresses can be
written as:


   216.3.128.129/28, 216.3.128.130/28, and etc.

With an introduction of CIDR addressing scheme, IP addresses are more efficiently allocated to ISPs and customers; and hence there is less risk of IP addresses running out anytime soon. For detailed specification on CIDR, please review RFC 1519. With introduction of additional gaming, medical, applicance and telecom devices requiring static IP addresses in addition to more than 6.5 billion (July 2006 est.) world population, the IPv4 addresses with CIDR addressing scheme will eventually run out. To solve shortage of IPv4 addresses, the IPv6 (128-bit) address scheme was introduced in 1993.

What is IPv6 Address?

Internet Protocol Version 6 (or IPv6) is a successor of IPv4 Address standard developed by IETF, which is designed to solve IPv4 address exhaustion problem. IPv4 uses a 32-bit numbering scheme to represent an IP address, which has an address space of 232 or 4.3 billion. IPv6, on the other hand, uses 128-bit numbering scheme (2128) which has big enough address space for many decades to come. IPv6 is intended to replace the IPv4, but the introduction of CIDR (Classless Inter-Domain Routing) allocation scheme in 1993 within the IPv4 prolonged lifespan of IPv4 Addresses. With an anticipation of smartphones, tablets, smart appliances and other electronic devices joining Internet every day, IPv4 address space will eventually exhaust. As of May 2014 per Google Statistics, 96% of Internet traffic is IPv4 and only 4% is represented by IPv6. IPv4 and IPv6 are not interoperable by design, so the transition from IPv4 to IPv6 require "transition mechanism" such as Stateless IP/ICMP Translation, Transport Relay, 6rd and other IPv6 transition mechanisms to make them interoperable.

IPv6 Address Types

IPv6 addresses are classified into three categories: unicast, anycast and multicast addressing.

Unicast Address - An unicast IP address is an identifier for a single network interface. An IPv6 packet sent to an unicast address is delivered to a single interface.

Anycast Address - An anycast IP address is identifier for a set of interfaces assigned to a group but belonging to different nodes. An IPv6 packet sent to an anycast address is delivered to a single node closest to the sender identified by the routing algorithm.

Multicast Address - A multicast IP address is identifier for a set of interfaces that may belong to differentn nodes. An IPv6 packet sent to a multicast address is delivered to all interfaces identified by the multicast address.

Unlike IPv4 addressing scheme, the IPv6 addressing scheme does not implement broadcast address. Instead, IPv6 implements multicast address to send packets to a group of nodes and avoids distributing to every nodes in the network. IPv6 also has a scope, which specifies which part of the network it's address is valid and unique.

Coloned Decimals

The IPv6 addresses are comprised of 128-bits (or 8 groups of 4 hexadecimal digits separated by colons), with possibility of omitting zeros to abbreviate the full address. An example of IPv6 address may look like 2001:0db8:0012:0001:3c5e:7354:0000:5db1. For convenience, an IPv6 address can be represented in shorter notation by omitting leading zeros. The example address above can be also be represented as 2001:db8:12:1:3c5e:7354:0:5db1.

When abbreviating IPv6 address, the following rules apply:

One or more leading zeros in any group of 8 hexadecimal digits can be removed. For example, 0012 can be written 12 and 0000 can be converted to 0. (see example above).

Consecutive group of zeros are replaced with a double colon ::. The loopback address, 0000:0000:0000:0000:0000:0000:0000:0001 can be abbreviated to ::1.

What are the differences between IPv4 and IPv6?

The IPv4 and IPv6 share a similar architecture, and they will coexist until IPv6 completely replaces the IPv4.

IPv4 is represented by 32-bit number, and IPv6 is represented by 128-bit number. This translates to 4.3 billion address space for IPv4 and 340 trillion address space for IPv6.

IPv4 is separated by 4 groups of 2 hexadecimal digits by a dot, whereas IPV6 is separated by 8 groups of 4 hexadecimal digits by a colon.

IPv4 does not support short-hand notation, but IPv6 does by omitting leading zeros.

Why is IPv6 matter?

With an explosive demand for smartphones, tablets and computers, more IP addresses are needed than IPv4 can support. There are over 7 billion people in the world with phones, tablets and computers each requiring an IP address. The IPv4 has an address space of 4.3 billion, which will soon exhaust. The transition from IPv4 to IPv6 is necessary, and they will coexist as they are not interoperable.

The users will not likely notice the difference or even notice it. With over 95% of IP addresses being IPv4, it will be quiet some time before we'll see all devices communicating via IPv6.