IPv6 Description

IP Address:

An Internet Protocol (IP) address is a numerical label that is assigned to devices participating in a computer network that uses the Internet Protocol for communication between its nodes.

An IP address serves two principal functions: host or network interface identification and location addressing. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there."

The designers of TCP/IP defined an IP address as a 32-bit number [1] and this system, known as Internet Protocol Version 4 or IPv4, is still in use today. However, due to the enormous growth of the Internet and the resulting depletion of available addresses, a new addressing system (IPv6), using 128 bits for the address, was developed in 1995

It was last standardized by RFC 2460 in 1998. Although IP addresses are stored as binary numbers, they are usually displayed in human-readable notations, such as 208.77.188.166 (for IPv4), and 2001:db8:0:1234:0:567:1:1 (for IPv6).

The Internet Protocol also routes data packets between networks; IP addresses specify the locations of the source and destination nodes in the topology of the routing system. For this purpose, some of the bits in an IP address are used to designate a subnetwork. The number of these bits is indicated in CIDR notation, appended to the IP address; e.g., 208.77.188.166/24.

As the development of private networks raised the threat of IPv4 address exhaustion, RFC 1918 set aside a group of private address spaces that may be used by anyone on private networks. They are often used with network address translators to connect to the global public Internet.

The Internet Assigned Numbers Authority (IANA), which manages the IP address space allocations globally, cooperates with five Regional Internet Registries (RIRs) to allocate IP address blocks to Local Internet Registries (Internet service providers) and other entities.

IPv6:

The rapid exhaustion of IPv4 address space, despite conservation techniques, prompted the Internet Engineering Task Force (IETF) to explore new technologies to expand the Internet's addressing capability. The permanent solution was deemed to be a redesign of the Internet Protocol itself. This next generation of the Internet Protocol, aimed to replace IPv4 on the Internet, was eventually named Internet Protocol Version 6 (IPv6) in 1995. The address size was increased from 32 to 128 bits or 16 octets, which, even with a generous assignment of network blocks, is deemed sufficient for the foreseeable future. Mathematically, the new address space provides the potential for a maximum of 2128, or about 3.403 × 1038 unique addresses.

The new design is not based on the goal to provide a sufficient quantity of addresses alone, but rather to allow efficient aggregation of subnet routing prefixes to occur at routing nodes. As a result, routing table sizes are smaller, and the smallest possible individual allocation is a subnet for 264 hosts, which is the square of the size of the entire IPv4 Internet. At these levels, actual address utilization rates will be small on any IPv6 network segment. The new design also provides the opportunity to separate the addressing infrastructure of a network segment—that is the local administration of the segment's available space—from the addressing prefix used to route external traffic for a network. IPv6 has facilities that automatically change the routing prefix of entire networks should the global connectivity or the routing policy change without requiring internal redesign or renumbering.

The large number of IPv6 addresses allows large blocks to be assigned for specific purposes and, where appropriate, to be aggregated for efficient routing. With a large address space, there is not the need to have complex address conservation methods as used in classless inter-domain routing (CIDR).

All modern desktop and enterprise server operating systems include native support for the IPv6 protocol, but it is not yet widely deployed in other devices, such as home networking routers, voice over Internet Protocol (VoIP) and multimedia equipment, and network peripherals.

IPv6 features include:

• Supports source and destination addresses that are 128 bits (16 bytes) long.
• Requires IPSec support.
• Uses Flow Label field to identify packet flow for QoS handling by router.
• Allows the host to send fragments packets but not routers.
• Doesn't include a checksum in the header.
• Uses a link-local scope all-nodes multicast address.
• Does not require manual configuration or DHCP.
• Uses host address (AAAA) resource records in DNS to map host names to IPv6 addresses.
• Uses pointer (PTR) resource records in the IP6.ARPA DNS domain to map IPv6 addresses to host names.
• Supports a 1280-byte packet size (without fragmentation).
• Moves optional data to IPv6 extension headers.
• Uses Multicast Neighbor Solicitation messages to resolve IP addresses to link-layer addresses.
• Uses Multicast Listener Discovery (MLD) messages to manage membership in local subnet groups.
• Uses ICMPv6 Router Solicitation and Router Advertisement messages to determine the IP address of the best default gateway.