Internet Blog

IPv6 are next generation of IPv4. The addressing scheme used for the TCP/IP protocols is called IP version 4 (IPv4). This scheme uses a 32-bit binary number to identify networks and end stations. This 32-bit scheme yields about 4 billion addresses, but because of the dotted decimal system (which breaks the number into four sections of 8 bits each) and other considerations, only about 250 million usable addresses exist. When the scheme was originally developed in the 1980s, no one ever thought that address would become scarce. The advent of the Internet, however, along with the trend of making many devices Internet-compatible (which means they need an address), such as cell phones and PDAs, makes running out of IPv4 addresses a certainty.


Network Address Translation (NAT) and Port Address Translation (PAT) were developed as solutions to the diminishing availability of IP addresses. NAT and PAT enable a company or user to share a single (or a few) assigned IP addresses among several private addresses that are not bound by an address authority. Although these schemes preserve address space and provide anonymity, the benefits come at the cost of individuality, which goes against the very reason for networking in the first place, which is to allow peer-to-peer collaborations through shared applications.

IP addressing scheme version 6 (IPv6) not only provides an answer to the problem of depleting address space, it allows for the restoration of a true end-to-end model, where hosts can connect to each other unobstructed and with greater flexibility. The key elements in IPv6 are to allow for each host to have a unique global IP address, to maintain connectivity even when in motion, and to natively secure host communications.

IPv6 Addresses The 128-bit address used in IPv6 allows for a greater number of addresses and subnets (enough space for 1015 end points - 340,282,366,920,938,463,463, 374,607,431,768,211,456 total).

IPv6 was designed to give every user multiple global addresses that can be used for a variety of devices, including cell phones, PDAs, IP-enabled vehicles, and consumer electronics. In addition to providing more address space, IPv6 has the following advantages over IPv4:

* Easier address management and delegation
* Easy address autoconfiguration
* Embedded IPSec (encrypted security)
* Optimized routing
* Duplicate Address Detection (DAD)

IPv6 Notation
This figure demonstrates the notation and shortcuts for IPv6 addresses.

128 bits are expressed as 8 fields of 16 bits in Hex notation:
2031 :0000:130F:0000:0000:09C0:876A:130B

An IPv6 address uses the first 64 bits in the address for the network ID and the second 64 bits for the host ID. The network ID is separated into "prefix" chunks. This figure shows the address hierarchy.

IPv6 Autoconfiguration
IPv4 deployments use one of two methods to assign IP addresses to a host: static assignment (which is management intensive) or DHCP/BOOTP, which automatically assigns IP addresses to hosts upon booting onto the network.

IPv6 provides a feature called stateless auto con figuration that is similar to Dynamic Host Configuration Protocol (DHCP). Using stateless configuration, any router interface that has an IPv6 address assigned to it becomes the "provider" of IP addresses on the network to which it’s attached. Safeguards are built into IPv6 that prevent duplicate addresses. This feature is called Duplicate Address Detection (DAD).

IPv6 Security
IPv6 has embedded support for IPSec. The host operating system (OS) can configure an IPSec tunnel between the host and any other host that has IPv6 support.

NAT and PAT
Although Network Address Translation (NAT) causes problems with peer-to-peer collaboration, it is still widely used, particularly in homes and small offices.

* Static NAT uses a one-to-one private-to-public address translation.
* Dynamic NAT matches private addresses to a pool of public addresses on an as-needed basis. The address translation is still one to one.

Port Address Translation (PAT) is a form of dynamic address translation that uses a many private addresses to few or one public address. This is referred to as overloading. It is accomplished by assigning port numbers.