Internet Protocol Version 6 (IPv6)

Currently we are using Internet protocol Version 4 (IPv4). Most of Today's Internet uses IPv4 which is nearly twenty years old. IPv4 has proven to be robust, easily implemented and interoperable. All we know that each device in a network has it's own unique IP address. IPv4 supports 2³² (4,294,967,296) addresses. So it is impossible to give even one address to every living person. In future so many devices will be connected in networks. So there is shortage of IPv4 Addresses in near future. So we must need next generation protocol.

Internet Protocol Version 6 (IPv6) is the next generation protocol. IPv6 supports 2¹²⁸ (340,282,366,920,938,463,463,374,607,431,768,211,456)addresses. Approximately 5 x 10²⁸ addresses for every living person. 128 bit address space provides 655,570,793,348,866,943,898,599 addresses for every square meter of the Earth's surface. IPv6 is expected to gradually replace IPv4. IPv6 fixes a number of problems in IPv4.

It is expected that IPv4 will be supported alongside IPv6 for the foreseeable future. IPv4 only clients/servers will not be able to communicate directly with IPv6 clients/servers, and will require service specific intermediate servers or NAT PT protocol translation servers.

Features of IPv6:

Larger Address space
The addresses of IPv 6 are 128 bits long. 128 bits can express over 3.4 x 10³⁸ possible combinations. The bottom 64 bits would be used for Mac Address of the network card and top 64 bits would be used for routing purposes.

New header format
The new IPv6 header is twice as large as the IPv4 header. The IPv6 header has a new format which keeps header overhead to a minimum. This is achieved by moving both non essential fields and optional fields to extension headers that are placed after the IPv6 header. The streamlined IPv6 header is more efficiently processed at intermediate routers.

Efficient and hierarchical addressing and routing infrastructure
IPv6 global addresses are designed to create an efficient, hierarchical, and summarizable routing infrastructure that is based on the common occurrence of multiple levels of Internet service providers.

Stateless and Stateful Address Configuration
IPv6 supports both stateful address configuration(address configuration in the presence of a DHCP server) and stateless address configuration(address configuration in the absence of a DHCP server). This simplifies host configuration.

IPv6 hosts can be configured automatically. When first connected to a network, a host sends a link local multicast request for its configuration parameters, if configured suitably, routers respond to such a request with a router advertisement packet that contains network layer configuration parameters.

If IPv6 autoconfiguration is not suitable, a host can use stateful autoconfiguration (DHCPv6) or be configured manually. Stateless autoconfiguration is only suitable for hosts, routers must be configured manually or by other means.

Extensibility
We can extend IPv6 easily for new features by adding extension headers after the IPv6 header. IPv4 header supports 40 bytes of options where as the size of IPv6 extension headers is constrained by the size of the IPv6 packet only.

Network Layer Security
IPsec is an integral part of IPv6. IPsec is the protocol for IP network layer encryption and authentication. This protocol provides a standards based solution for network security needs and promotes interoperability between different IPv6 implementations. IPsec support is optional in IPv4.

Faster Routing Performance
The routing performance is faster in IPv6 by using a simpler and more systematic header structure.

Packet Limit
packets are limited to 64 KiB of payload in IPv4. IPv6 has support for for packets over this limit.

Multicast Addresses
In IPv4 Broadcast addresses are used to send traffic to all nodes on a subnet. In IPv6 there are no IPv6 broadcast addresses. A link local scope all nodes multicast address is used in IPv6 instead of broadcast addresses. A multicast address identifies multiple interfaces. Packets addressed to a multicast address are delivered to all interfaces that are identified by the address.

IPv6 Address Notation
IPv6 addresses are represented in eight groups of four hexadecimal digits separated by colons. In IPv6, the 128 bit address is devided into eight 16 bit blocks and each 16 bit block is converted to a 4 digit Hexaecimal number and separated by colons.

The following is an valid IPv6 Address in colon hexadecimal format.
2001:0db8:0000: 08d3:1319:8a2e: 00ff: 02aa

In binary form the above one is divided along 16-bit boundaries like this
0010000000000001 0000110110111000 0000000000000000 0000100011010011 0001001100011001 1000101000101110 0000000011111111 0000001010101010

The above IPv6 address in colon hexadecimal format can be futher simplied by removing leading zeros in each 4 digit hexadecimal block. But each block must have atleast a single digit. So the above address can be simplied like below.
2001:db8:0:8d3:1319:8a2e:ff:2aa

For example take this address 2001:db8:0:0:0:0:ff:2aa We can further simplify this type of addresses. A contiguous sequence of 16 bit blocks set to 0 in the colon hexadecimal format can be replaced by “::” ,that is double colon. So we can simplify above address like below.
2001:db8::ff:2aa

In URL's IPv6 address is enclosed in brackets as shown below.
http://[ 2001:db8:0:8d3:1319:8a2e:ff:2aa]/
With this type of notation we can not confuse between IPv6 address and port number as shown below.
http://[ 2001:db8:0:8d3:1319:8a2e:ff:2aa]:220/

IPv6 address types
IPv6 addresses are of three types Unicast,Multicast and Anycast.

A unicast address identifies a single interface within the scope of the type of unicast address. Packets addressed to a unicast address are delivered to a single interface.

A multicast address identifies multiple interfaces. Packets addressed to a multicast address are delivered to all interfaces that are identified by the address.

An anycast address identifies multiple interfaces. Packets addressed to anycast address are delivered to a single interface, that is the nearest interface that is identified by the address.

Microsoft has implemented IPv6 protocol for Windows XP SP1, XP SP2, Windows server 2003 family, Windows CE.NET version 4.1 and later. This can be can be installed and uninstalled as a network protocol through the Network Connections folder.

Microsoft has implemented Next Generation TCP/IP stack in Windows Vista and Windows server Longhorn. The Next Generation TCP/IP stack supports the dual IP layer architecture in which the IPv4 and IPv6 implementations share common Transport and framing layers. The Next Generation TCP/IP stack has both IPv4 and IPv6 installed and enabled by default. There is no need to install a separate component to obtain IPv6 support.