The first tutorial in this series considered the history and requirements for Internet Protocol version 6, or IPv6, which has been developed by the Internet Protocol – Next Generation (IPng) Working Group within the Internet Engineering Task Force (IETF). This tutorial will extend that discussion and consider the enhanced capabilities that have been designed into the new protocol.
IETF Request for Comments (RFC) 1752, published in 1995, described the important features required of IPng, formally designated IPv6. In the decade or so since that publication, many other RFC documents have been released which provide additional technical details, and build on industry testing and implementation experience. These key capabilities include:
Expanded addressing and routing: increasing the IP address field from 32 to 128 bits in length, which allows for a much greater number of addressable nodes, more levels of addressing hierarchy, defining new types of addresses, and so on. Without a doubt, the addressing enhancements have received the most attention, including the infamous Date of Doom (which some thought to be March 1994) – the date when the IPv4 Class B address space (the format used by most enterprises) would be exhausted. That date came and went, and for the most part, we are still OK. Nevertheless, considerable work has gone into this subject matter, including the publication of RFC 4291, titled IPv6 Addressing Architecture which provides the necessary details.
Simplified header format: eliminating or making optional some of the IPv4 header fields to reduce the packet handling overhead, thus providing some compensation for the larger addresses. Even with the addresses, which are four times as long, the IPv6 header is only 40 octets in length, compared with 20 octets for IPv4 (an octet is an eight bits in length). The IPv6 header is described in RFC 2460, IPv6 Specification.
Extension headers and options: IPv6 protocol options are placed in separate headers, located after the core IPv6 header information, such that processing at every intermediate stop between source and destination may not be required. These options, along with the simplified header format noted above, streamline the IPv6 packet delivery, improving router processing time when compared with IPv4.
Authentication and privacy: all implementations of IPv6 must have the capabilities to authenticate the sender of a packet and encrypt the contents of that packet, as required. This work is part of a larger effort to enhance IP security in general, called IPsec, which is documented in RFC 4301, Security Architecture for the Internet Protocol.
Auto-reconfiguration: the plug and play capabilities, which include support from node address assignments up to the use of the Dynamic Host Reconfiguration Protocol (DHCP). The function is vital for enterprise IPv6 deployment, as it eliminates some, if not all, of the human intervention associated with assigning addresses to workstations. A process known as Stateless Auto-configuration is detailed in RFC 2462, with the enhanced DHCPv6 (the stateful counterpart) described in RFC 3315.
Source routes: support for a header compatible with the Source Demand Routing Protocol (SDRP) , such that a source-selected route may complement the route determined by the existing routing protocols. This process is described in RFC 1940.
Simple and flexible transition: a plan for the transition from IPv4 to IPv6 with four basic requirements:
Incremental upgrade: allowing existing IPv4 hosts to be upgraded at any time without a dependency on other hosts or routers being upgraded.
Incremental deployment: new IPv6 hosts and routers can be installed at any time without any prerequisites.
Easy addressing: when existing installed IPv4 hosts or routers are upgraded to IPv6, they may continue to use their existing address without needing a new assigned address.
Low start-up costs: little or no preparation work is needed in order to upgrade existing IPv4 systems to IPv6 or to deploy new IPv6 systems.
Two mechanisms have been developed to support this transition, called dual stack, and configured tunneling. These mechanisms are detailed in RFC 4213, Basic Transition Mechanisms for IPv6 Hosts and Routers.
Quality of service capabilities: a new capability is added to enable the labeling of packets belonging to particular traffic "flows" for which the sender has requested special handling, such as non-default quality of service or "real-time" service. The operation of the flow label (part of the IPv6 header) is defined in RFC 3697, IPv6 Flow Label Specification.
Thus, the foreseeable exhaustion of the available IPv4 address space gave the Internet community the impetus to consider revisions to this widely deployed protocol. But other factors, such as support for real-time applications and enhanced security, may be equally important – if not more important – to your enterprise.
But you don't have to jump into IPv6 alone. Our next tutorial will examine the various industry forums and experimental networks that have been developed to test these new IPv6 capabilities.
Copyright Acknowledgment: (c) 2007 DigiNet Corporation(R), All Rights Reserved
Mark A. Miller, P.E. is President of DigiNet Corporation(R), a Denver-based consulting engineering firm. He is the author of many books on networking technologies, including Implementing IPv6, and the Internet Technologies Handbook, both published by John Wiley & Sons.
Article courtesy of internetnews.com