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Dated: Aug. 13, 2004

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Networking In General

IPng short for Internet Protocol next generation, a new version of the Internet Protocol (IP) currently being reviewed in IETF standards committees. The official name of IPng is IPv6, where the v6 stands for version 6. The current version of IP is version 4, so it is sometimes referred to as IPv4.

IPng is designed as an evolutionary upgrade to the Internet Protocol and will, in fact, coexist with the older IPv4 for some time. IPng is designed to allow the Internet to grow steadily, both in terms of the number of hosts connected and the total amount of data traffic transmitted.

Due to recent concerns over the impending depletion of the current pool of Internet addresses and the desire to provide additional functionality for modern devices, an upgrade of the current version of the Internet Protocol (IP), called IPv4, is in the process of standardization. This new version, called IP Version 6 (IPv6), resolves unanticipated IPv4 design issues and is poised to take the Internet into the 21st Century.When the Internet was in its early years, its designers had developed a system that allowed four billion

Internet addresses, a huge figure representing the number of users, to communicate each other online at a time.

Today about 6 billion people inhabit the earth. They own an estimated 350 million computers and 480 million mobile phones. The number of mobile phones and PDAs is expected to reach one billion by 2003.

The reason we are quickly moving beyond the capabilities of the current protocol has a lot to do with the propagation of wireless devices and new services, as well as the subsequent of massive demand for more addressees.

The very concept of computers is changing rapidly as cars, vending machines and even house hold applications follow the lead of the PC and become connected to the Internet. Each one will require its own unique address.

It is estimated that within seven to ten years a single user will manage an average of 10 addresses and this number could grow higher in future. Wireless gambling, music on demand, video content and video conferencing are becoming a reality. With IP V-6 every person on earth could have a million uniquely addressees and the individually locatable IP devices. With this kind of capability we could create the potential for virtually unlimited access to the Internet for nay number and variety of devises.


IPv6 Features

The Following Are The Features Of The Ipv6 Protocol:

  • New header format

  • Large address space

  • Efficient and hierarchical addressing and routing infrastructure

  • Stateless and stateful address configuration

  • Built-in security

  • Better support for QoS

  • New protocol for neighboring node interaction

  • Extensibility

The following sections discuss each of these new features in detail.

New Header Format

The IPv6 header has a new format that is designed to keep 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.

IPv4 headers and IPv6 headers are not interoperable. IPv6 is not a superset of functionality that is backward compatible with IPv4. A host or router must use an implementation of both IPv4 and IPv6 in order to recognize and process bo th header formats. The new IPv6 header is only twice as large as the IPv4 header, even though IPv6 addresses are four times as large as IPv4 addresses.

Large Address Space

IPv6 has 128-bit (16-byte) source and destination IP addresses. Although 128 bits can express over 3.4"e1038 possible combinations, the large address space of IPv6 has been designed to allow for multiple levels of subnetting and address allocation from the Internet backbone to the individual subnets within an organization.

Even though only a small number of the possible addresses are currently allocated for use by hosts, there are plenty of addresses available for future use. With a much larger number of available addresses, address-conservation techniques, such as the deployment of NATs, are no longer necessary.

Efficient and Hierarchical Addressing and Routing Infrastructure

IPv6 global addresses used on the IPv6 portion of the Internet 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. On the IPv6 Internet, backbone routers have much smaller routing tables, corresponding to the routing infrastructure of global ISPs. For more information, see "Aggregatable Global Unicast Addresses."

Stateless and Stateful Address Configuration

To simplify host configuration, IPv6 supports both stateful address configuration, such as address configuration in the presence of a DHCP server, and stateless address configuration (address configuration in the absence of a DHCP server). With stateless address configuration, hosts on a link automatically configure themselves with IPv6 addresses for the link (called link-local addresses) and with addresses derived from prefixes advertised by local routers. Even in the absence of a router, hosts on the same link can automatically configure themselves with link-local addresses and communicate without manual configuration.

Built-In Security

Support for IPsec is an IPv6 protocol suite requirement. This requirement provides a standards-based solution for network security needs and promotes interoperability between different IPv6 implementations.

Better Support for QoS

New fields in the IPv6 header define how traffic is handled and identified. Traffic identification using a Flow Label field in the IPv6 header allows routers to identify and provide special handling for packets belonging to a flow, a series of packets between a source and destination. Because the traffic is identified in the IPv6 header, support for QoS can be achieved even when the packet payload is encrypted through IPsec.

New Protocol for Neighboring Node Interaction

The Neighbor Discovery protocol for IPv6 is a series of Internet Control Message Protocol for IPv6 (ICMPv6) messages that manage the interaction of neighboring nodes (nodes on the same link). Neighbor Discovery replaces the b roadcast-based Address Resolution Protocol (ARP), ICMPv4 Router Discovery, and ICMPv4 Redirect messages with efficient multicast and unicast Neighbor Discovery messages.


IPv6 can easily be extended for new features by adding extension headers after the IPv6 header. Unlike options in the IPv4 header, which can only support 40 bytes of options, the size of IPv6 extension headers is only constrained by the size of the IPv6 packet.

Types of IPv6 Addresses

There are three types of IPv6 addresses:

  1. Unicast
    A unicast address identifies a single interface within the scope of the type of unicast address. With the appropriate unicast routing topology, packets addressed to a unicast address are delivered to a single interface. To accommodate load-balancing systems, RFC 2373 allows for multiple interfaces to use the same address as long as they appear as a single interface to the IPv6 implementation on the host.

  2. Multicast
    A multicast address identifies multiple interfaces. With the appropriate multicast routing topology, packets addressed to a multicast address are delivered to all interfaces that are identified by the address.

  3. Anycast
    An anycast address identifies multiple interfaces. With the appropriate routing topology, packets addressed to an anycast address are delivered to a single interface, the nearest interface that is identified by the address. The nearest interface is defined as being closest in terms of routing distance. A multicast address is used for one-to-many communication, with delivery to multiple interfaces. An anycast address is used for one-to-one-of-many communication, with delivery to a single interface.In all cases, IPv6 addresses identify interfaces, not nodes. A node is identified by any unicast address assigned to one of its interfaces. 

    RFC 2373 does not define a broadcast address. All types of IPv4 broadcast addressing are performed in IPv6 using multicast addresses. For example, the subnet and limited broadcast addresses from IPv4 are replaced with the link-local scope all-nodes multicast address of FF02::1.

Links and Subnets

Similar to IPv4, an IPv6 subnet prefix (subnet ID) is assigned to a single link. Multiple subnet IDs can be assigned to the same link. This technique is called multinetting.

Special IPv6 Addresses

The following are special IPv6 addresses:

Unspecified address

The unspecified address (0:0:0:0:0:0:0:0 or ::) is only used to indicate the absence of an address. It is equivalent to the IPv4 unspecified address of The unspecified address is typically used as a source address for packets attempting to verify the uniqueness of a tentative address. The unspecified address is never assigned to an interface or used as a destination address.

Loopback address

The loopback address (0:0:0:0:0:0:0:1 or ::1) is used to identify a loopback interface, enabling a node to send packets to itself. It is equivalent to the IPv4 loopback address of Packets addressed to the loopback address must never be sent on a link or forwarded by an IPv6 router.

IPv6 and DNS

Enhancements to the Domain Name System (DNS) for IPv6 are described in RFC 1886 and consist of the following new elements:

Host address (AAAA) resource record

IP6.INT domain for reverse queries

The Host Address (AAAA) Resource Record

A new DNS resource record type, AAAA (called "quad A"¨), is used for resolving a fully qualified domain name to an IPv6 address. It is comparable to the host address (A) resource record used with IPv4. The resource record type is named AAAA (Type value of 28) because 128-bit IPv6 addresses are four times as large as 32-bit IPv4 addresses. The following is an example of a AAAA resource record: IN AAAA FEC0::2AA:FF:FE3F:2A1C

A host must specify either a AAAA query or a general query for a specific host name in order to receive IPv6 address resolution data in the DNS query answer sections.

The IP6.INT Domain

The IP6.INT domain has be en created for IPv6 reverse queries. Also called pointer queries, reverse queries determine a host name based on the IP address. To create the namespace for reverse queries, each hexadecimal digit in the fully expressed 32-digit IPv6 address becomes a separate level in inverse order in the reverse domain hierarchy.

For example, the reverse lookup domain name for the address FEC0::2AA:FF:FE3F:2A1C (fully expressed as FEC0:0000:0000:0000:02AA: 00FF:FE3F:2A1C) is:C.1.A.2.F.3.E.F.F.F.0.0.A.A. DNS support described in RFC 1886 represents a simple way to both map host names to IPv6 addresses and provide reverse name


The implementation of IPV-6 must be accomplished in a manner least disruptive to the network, the operators and the end users. We advocate a smooth IPV-4 and IPV-6 during the transition and are working on such alternatives.

Most people understand the value of IPV-6 but they also understand the challenges ahead in getting it deployed, and that's what's; holding them back. Internetworking IPV-4 and IPV-6 will be difficult but not impossible. IPV-6 will happen; it is only a question of how so.

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