Introduction to IPv6

Microsoft is delivering support for the emerging update to the Internet Protocol, commonly referred to as IP version 6 — or simply IPv6 (RFC 2460). This protocol suite is based on a standard from the Internet the Engineering Task Force (IETF) and it is designed to significantly increase size of the address space used to identify communication endpoints in the Internet, thereby allowing it to continue it’s tremendous growth rate. As a core networking protocol in Windows Server 2003, IPv6 serves as one of two Internet protocols that enable computers running Windows to communicate on intranets and over the Internet.

I Pv6 will continue the tradition of the IPv4 protocol, which gained much of its acceptance by defining mechanisms to tie systems together over a wide variety of disparate networking technologies. Already defined link- layer mappings for transporting IPv6 include Ethernet, Point-to-Point Protocol (PPP), Fiber Distributed Data Interface (FDDI), Token Ring, Asynchronous Transfer Mode (ATM), Frame Relay, and IEEE 1394. From an architectural perspective, an IPv4-based infrastructure appears to systems that are enabled for IPv6 as a single segment non-broadcast multi-access (NBMA) network. The capability to send IPv6 traffic over existing IPv4 networks will provide an initial reach as broad as the current Internet, limited only by the endpoints’ ability and readiness to make use of it.

New capabilities that are expected to drive rapid adoption include scoped addresses; stateless auto configuration, which lowers complexity and management burden; and mandatory IP security (IPSec), which permits end-to-end data authentication and integrity and increases privacy of connections. In addition, technologies that extends the lifetime of IPv4 (such as network address translation, or NATs) frequently do not work with existing applications, and those technologies are already restricting the flexibility to deploy new applications. NATs are popular today because they allow multiple systems to share a single public IPv4 address. However, they tend to enforce a client/server usage model where the client uses private address space with only the server existing in public address space. IPv6 brings back the capability of “end-to-end control of communications,” making networking applications simpler as the network again becomes transparent.


IPv6 increases the IP address size from 32 bits to 128 bits, to support more levels of addressing hierarchy, a much greater number of addressable nodes and simpler auto-configuration of addresses. Scalability of multicast addresses is introduced. A new type of address called an any cast address is also defined, to send a packet to any one of a group of nodes.

Improved Support for Extensions and Options

IPv6 options are placed in separate headers that are located between the IPv6 header and the transport layer header. Changes in the way IP header options are encoded allow more efficient forwarding, less stringent limits on the length of options, and greater flexibility for introducing new options in the future. The extension headers are: Hop-by-Hop Option, Routing (Type 0), Fragment, Destination Option, Authentication, and Encapsulation Payload.

Flow labeling capability –

A new capability has been added to enable the labeling of packets belonging to particular traffic flows for which the sender requests special handling, such as non-default Quality of Service or real-time service.