Friday, March 02, 2012

Internet Protocol address ( IP ) Address


What is an IP address ?
“IP address” is a shorter way of saying “Internet Protocol address.” IP addresses are the numbers assigned to computer network interfaces. Although we use names to refer to the things we seek on the Internet, such as www.example.org, computers translate these names into numerical addresses so they can send data to the right location. So when you send an email, visit a web site, or participate in a video conference, your computer sends data packets to the IP address of the other end of the connection and receives packets destined for its own IP address.

Why do we need IP addresses ?
IP addresses are the numbers that enable our computers, servers, telephones, cameras, printers and sensors to communicate with each other. Without IP addresses, we would have to copy data from device to device manually, using CDs, DVDs, hard disks or flash storage, such as a USB drive. But more importantly, our devices could not send data to each other without human intervention. Without the IP addresses assigned to our computers, we would have to send paper letters and memos instead of sending emails. There would be no streaming video sites. Instead, we would have to send each other discs and tapes. Worst of all, we would not be able to order items online and would have to go to stores to buy them in person. It would be horrific, like the 1970s all over again.


What is the difference between a private IP address and a unique IP address ?
Private addresses are the addresses people use on private networks, such as many home and office networks. At a protocol level there is no difference between the addresses, but organizationally, private addresses are distinct because they can only be used within a single administration and not on the wider Internet. This is because private addresses are set aside for use by anyone without any global coordination. You can know an address is from a block of private addresses if it:
■■ Begins with 10. (i.e. 10.0.0.0 through 10.255.255.255)
■■ Begins with 172.16. through 172.31.
■■ Begins with 192.168.
These addresses are the defaults used in a lot of plug’n’play networking equipment, like that sold to residential Internet users. Unique addresses are different only in that their distribution is managed by a set of registries. Because the registries manage the distribution of the other addresses, it is possible to know who an address is assigned to and how to get in contact with them. These types of addresses allow data to be routed across the whole Internet.
If your computer is assigned a private address, but you can still access services over the Internet, then your computer is probably behind a Network Address Translator (NAT), which lets lots of computers share a single unique IP address.

How many  IP addresses do I use ?
Typically, a residential Internet connection is assigned one unique address and uses a block of private addresses to number each computer, printer, video game console, or smartphone connected to it. But while this address is assigned to the connection we use, the services and peers we communicate with on the Internet also have addresses. There are approximately 3.7 billion addresses available for ordinary Internet connections, and about 1.6 billion people used the Internet in 2009. So, very roughly, each user requires a little over two unique addresses.

What do IP addresses look like?
There are currently two different versions of IP addresses in use—IPv4 and IPv6. The two versions look quite different from one another. IP addresses are actually just long strings of numbers, like 3221226037, but to make it easier for people to read them, we write them down in a special way. IPv4 addresses are written as a string of four numbers between 0 and 255, separated by dots. A typical IPv4 address looks like this: 192.0.2.53.

IPv6 addresses are considerably longer strings of numbers, so they are written using hexadecimals, which can fit more information into fewer digits. Colons separate the segments of IPv6 addresses instead of dots; for example, 2001:0db8::53. In fact, when you see two colons side by side in an IPv6 address, you know that all the segments between them contain only zeros. Without those colons, the example address expands to its fully-written version, 2001:0db8:0000:0000:0000:0000:0000:0053.

What is IPv4’s history?
IPv4 has just over four billion unique IP addresses. It was developed in the early 1980s and served the global Internet community for more than three decades. But IPv4 is a finite space, and after years of rapid Internet expansion, its pool of available unallocated addresses has been fully allocated to Internet services providers (ISPs) and users.
Only 3.7 billion IPv4 addresses are usable by ordinary Internet access devices. The others are used for special protocols, like IP Multicasting. Almost three and a half billion addresses was enough for the experiment that the Internet started as in the 1980s, but it is not enough for a production network in today’s world, with its population of almost seven billion people.

What is IPv6’s history?
Standardized in 1996, IPv6 was developed as the next-generation Internet Protocol. One of its main goals was to massively increase the number of IP addresses available. The first production allocations were made to ISPs and other network operators in 1999, and by June 2006, IPv6 was successful enough that important test networks shut down. They were no longer needed.

Over the past year, major content providers and access networks have started offering IPv6 services to ordinary Internet users. Because IPv6 is so much larger than IPv4, it should last us considerably longer than the 30 years IPv4 has given us so far. But just how large is IPv6?

IPv6 is significantly bigger than IPv4. Compared to IPv4’s 32-bit address space of four billion addresses, IPv6 has a 128-bit address space, which is 340 undecillion addresses. That’s not a number you hear every day!

Using IPv6, ISPs generally assign many thousands of network segments, called a /64, to a single subscriber connection used in places such as a home, classroom, or business. Giving every person on Earth a connection with a /64 would barely dent the available IPv6 address space. In fact, while the Earth’s orbit around the Sun is only big enough to contain 3,262 Earths put side by side, it would take 21,587,961,064,546 Earths to use all the addresses in the part of the IPv6 space we now use.

Why does every device need an IP address?
IP addresses are the numbers that identify devices connected to a network. If your device only needs access to a local network, it can be identified with an address that has only a local context. These are called private addresses. But when your device needs to access services on other networks, it needs to use a unique address. In some cases, this is done by translating a private address into a unique address at the border between your network and your ISP’s network. This technology is called Network Address Translation, or NAT.
NAT has the advantage of allowing multiple devices to share a single, unique address, but it also has disadvantages. One of these is that the device doing the NAT must understand the protocol being used by the devices communicating through it. If the protocol you want to use is not supported by the NAT, you cannot use it. This can cause frustration when, for instance, you are unable to use your Voice over IP (VoIP) service from a hotel or airport lounge while travelling. But there is also a second problem. If a new NAT device does not support a protocol, it will stop the people using the network it serves from also using that protocol, unless it is replaced. This stifles innovation in the services that can be provided over the Internet. Losing innovation means losing access to new services that could enrich our lives. But the variability in the protocols supported by NATs means that services often either work or break depending on the equipment used by the network operator, not by the setup on the individual user’s computer.

Are the Internet and its technology ready for the transition to IPv6?
Most of the existing systems that we use today already support IPv6. If you’re using a laptop, odds are, it supports IPv6 and has done so for quite some time. IPv6 is not dramatically different on the network from IPv4, and the machines we used 30 years ago were capable of running IPv6. This means that if the kind of computers operating thirty years ago could run IPv6, then pretty much any cell phone (or even pocket calculator) could run IPv6 today, if you really wanted it to.

Will I be able to access the whole Internet as IPv6 use becomes more
common ?
Don’t worry—we’re not doomed. While an IPv4-only machine cannot communicate directly with an IPv6-only machine, there are a number of ways to get them to communicate when using protocol translators. Also, ISPs are developing and deploying new access mechanisms that will allow new Internet users some IPv4 connectivity through multiple layers of private addressing.

How can I get IPv6 connectivity?
If you’re an average home user, your ISP will initiate the transition from IPv4 to IPv6 on your network. In most cases, you won’t have to do anything. If you are required to change something, such as your Internet router, your ISP will let you know.