Expanding the Embedded Universe: Migrating From IPv4 to IPv6

Rex Smith

September 10, 2008

Rex SmithSeptember 10, 2008

The Internet Protocol (IP) developed during the mid-1970s, is the backbone of a family of protocols that includes TCP, UDP, RIP, and virtually every other protocol used for Internet communications.

The current version, IP version 4 (IPv4), has been in use for more than 20 years. IPv4 has proven to be amazingly adaptable over the years; however, the demands placed upon the protocol at its inception pale in comparison to the demands of the millions of hosts that are now connected to the Internet today.

IPv4 is finally beginning to show some chinks in its armor. IP version 6 (IPv6), designed as a successor to IPv4 deals with many of IPv4's shortcomings. This article touches upon three of the major problems found in IPv4 and how IPv6 corrects each of these problems.

A few of the major problems currently found in IPv4 include:

#1. Depleted Address Space
The main motivation for replacing IPv4 with something better is that the IPv4 address space will ultimately be exhausted. Estimates for the total depletion of the IPv4 address space vary from 2005 until 2018.

Most estimates put the date around 2008 to 2010. Despite the disagreements on when the address space will be depleted, most agree that it will definitely happen unless something better is put in place. Compounding the problem is the uneven distribution of the IPv4 address space across the globe.

#2. Flawed Addressing Architecture
IPv4 addresses do not provide an efficient and scalable hierarchical address space. That is, it is impossible for a single high-level address to represent many lower-level addresses or networks.

To picture what a hierarchical address space looks like, think of the telephone numbering system. Just by looking at the area code, one can immediately determine what city or region to route the call. With IPv4 routing becomes increasingly complicated and expensive as the size of the Internet grows.

#3. High Cost
Another criticism of IPv4 is the high cost and maintenance requirements of networks. A significant percentage of the cost of administering an IPv4 network is incurred in the initial configuration of network hosts. IPv4's limitations also aggravate the task of renumbering network devices, which is cumbersome to network administrators.

IPv6 To The Rescue
One of the common myths associated with IPv6 is that the only reason to adopt IPv6 is the impending depletion of the IPv4 address space. The expanded address space of IPv6 is not the only improvement made in the protocol, however.

IPv6 also offers improvements in: addressing architecture, a stateless address autoconfiguration mechanism, a less expensive address resolution protocol, header format simplification, the ability to detect and recover from a failed forward route, and an improved method to join and leave multicast groups.

To the end user, IPv6 offers obvious advantages. Because of IPv6's larger address capacity, it allows greater flexibility in allocating addresses and routing traffic " freeing device users to use the Internet as they always have, but now with even higher levels of seamless integration between devices (Figure 1 below).

Figure 1. IPv6 allows users to display/talk/show/interact with each other from device to device

Dual Stack Approach Eases Transition
The Internet will consist of a combination of IPv4 and IPv6 nodes for a period of time during the transition. Therefore, compatibility between IPv4 and IPv6 nodes is critical for a successful transition.

Because IPv6 is not backwards compatible with IPv4, a dual stack approach is needed to enable nodes to communicate over both IPv4 and IPv6 simultaneously. This approach paves the way for transition mechanisms that will enable the Internet to move to IPv6.

Although the dual stack approach is the recommended transition mechanism for networks, under certain circumstances, such dual stack configurations can also be used in IPv6-only mode for isolated IPv6 networks.

This removes the additional overhead of the IPv4 stack for those devices that do not require IPv4 tunneling. Additional capabilities include Neighbor Discovery, Multicast Listener Discovery, Tunneling, DNS for IPv6, IPv6 Extension Headers, and Ancillary Data.

Let's take a look at each of these in a bit more detail.

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