Reason For Using IPv6


Why We Need More Address Space
To comprehend the IP addressing issues facing network administrators today, consider that the IPv4 address space provides approximately 4,294,967,296 unique addresses. Of these, only 3.7 billion addresses are assignable because the IPv4 addressing system separates the addresses into classes and reserves addresses for multicasting, testing, and other specific uses.
Based on figures as recent as January 2007, about 2.4 billion of the available IPv4 addresses are already assigned to end users or ISPs. That leaves roughly 1.3 billion addresses still available from the IPv4 address space. Despite this seemingly large number, IPv4 address space is running out.
Over the past decade, the Internet community has analyzed IPv4 address exhaustion and published mountains of reports. Some reports predict IPv4 address exhaustion by 2010, and others say it will not happen until 2013.
The growth of the Internet, matched by increasing computing power, has extended the reach of IP-based applications.
The pool of numbers is shrinking for the following reasons:
Population growth - The Internet population is growing. In November 2005, Cisco estimated that there were approximately 973 million users. This number has doubled since then. In addition, users stay on longer, reserving IP addresses for longer periods and are contacting more and more peers daily.
Mobile users - Industry has delivered more than one billion mobile phones. More than 20 million IP-enabled mobile devices, including personal digital assistants (PDAs), pen tablets, notepads, and barcode readers, have been delivered. More and more IP-enabled mobile devices are coming online every day. Old mobile phones did not need IP addresses, but new ones do.
Transportation - There will be more than one billion automobiles by 2008. Newer models are IP-enabled to allow remote monitoring to provide timely maintenance and support. Lufthansa already provides Internet connectivity on their flights. More carriers, including ships at sea, will provide similar services.
Consumer electronics - The newest home appliances allow remote monitoring using IP technology. Digital Video Recorders (DVRs) that download and update program guides from the Internet are an example. Home networking can connect these appliances.
Movement to change from IPv4 to IPv6 has already begun, particularly in Europe, Japan, and the Asia-Pacific region. These areas are exhausting their allotted IPv4 addresses, which makes IPv6 all the more attractive and necessary. Japan officially started the move in 2000 when the Japanese government mandated the incorporation of IPv6 and set a deadline of 2005 to upgrade existing systems in every business and public sector. Korea, China, and Malaysia have launched similar initiatives.
In 2002, the European Community IPv6 Task Force forged a strategic alliance to foster IPv6 adoption worldwide. The North American IPv6 Task Force has set out to engage the North American markets to adopt IPv6. The first significant North American advances are coming from the U.S. Department of Defense (DoD). Looking into the future and knowing the advantages of IP-enabled devices, DoD mandated, as early as 2003, that all new equipment purchased not only be IP-enabled, but also be IPv6-capable. In fact, all U.S. government agencies must start using IPv6 across their core networks by 2008, and the agencies are working to meet that deadline.
The ability to scale networks for future demands requires a limitless supply of IP addresses and improved mobility that DHCP and NAT alone cannot meet. IPv6 satisfies the increasingly complex requirements of hierarchical addressing that IPv4 does not provide.
Given the huge installed base of IPv4 in the world, it is not difficult to appreciate that transitioning to IPv6 from IPv4 deployments is a challenge. There are, however, a variety of techniques, including an auto-configuration option, to make the transition easier. The transition mechanism you use depends on the needs of your network.
The figure compares the binary and alphanumeric representations of IPv4 and IPv6 addresses. An IPv6 address is a 128-bit binary value, which can be displayed as 32 hexadecimal digits. IPv6 should provide sufficient addresses for future Internet growth needs for many years to come. There are enough IPv6 addresses to allocate more than the entire IPv4 Internet address space to everyone on the planet.
So what happened to IPv5? IPv5 was used to define an experimental real-time streaming protocol. To avoid any confusion, it was decided to not use IPv5 and name the new IP protocol IPv6.
IPv6 would not exist were it not for the recognized depletion of available IPv4 addresses. However, beyond the increased IP address space, the development of IPv6 has presented opportunities to apply lessons learned from the limitations of IPv4 to create a protocol with new and improved features.
A simplified header architecture and protocol operation translates into reduced operational expenses. Built-in security features mean easier security practices that are sorely lacking in many current networks. However, perhaps the most significant improvement offered by IPv6 is the address autoconfiguration features it has.
The Internet is rapidly evolving from a collection of stationary devices to a fluid network of mobile devices. IPv6 allows mobile devices to quickly acquire and transition between addresses as they move among foreign networks, with no need for a foreign agent. (A foreign agent is a router that can function as the point of attachment for a mobile device when it roams from its home network to a foreign network.)
Address autoconfiguration also means more robust plug-and-play network connectivity. Autoconfiguration supports consumers who can have any combination of computers, printers, digital cameras, digital radios, IP phones, Internet-enabled household appliances, and robotic toys connected to their home networks. Many manufacturers already integrate IPv6 into their products.
Many of the enhancements that IPv6 offers are explained in this section, including:
Enhanced IP addressing
Simplified header
Mobility and security
Transition richness
Enhanced IP Addressing
A larger address space offers several enhancements, including:
Improved global reachability and flexibility.
Better aggregation of IP prefixes announced in routing tables.
Multihomed hosts. Multihoming is a technique to increase the reliability of the Internet connection of an IP network. With IPv6, a host can have multiple IP addresses over one physical upstream link. For example, a host can connect to several ISPs.
Autoconfiguration that can include data link layer addresses in the address space.
More plug-and-play options for more devices.
Public-to-private, end-to-end readdressing without address translation. This makes peer-to-peer (P2P) networking more functional and easier to deploy.
Simplified mechanisms for address renumbering and modification.
The IPv6 simplified header offers several advantages over IPv4:
Better routing efficiency for performance and forwarding-rate scalability
No broadcasts and thus no potential threat of broadcast storms
No requirement for processing checksums
Simplified and more efficient extension header mechanisms
Flow labels for per-flow processing with no need to open the transport inner packet to identify the various traffic flows
Enhanced Mobility and Security
Mobility and security help ensure compliance with mobile IP and IP Security (IPsec) standards functionality. Mobility enables people with mobile network devices-many with wireless connectivity-to move around in networks.
The IETF Mobile IP standard is available for both IPv4 and IPv6. The standard enables mobile devices to move without breaks in established network connections. Mobile devices use a home address and a care-of address to achieve this mobility. With IPv4, these addresses are manually configured. With IPv6, the configurations are dynamic, giving Ipv6-enabled devices built-in mobility.
IPsec is available for both IPv4 and IPv6. Although the functionalities are essentially identical in both environments, IPsec is mandatory in IPv6, making the IPv6 Internet more secure.
Transition Richness
IPv4 will not disappear overnight. Rather, it will coexist with and then gradually be replaced by IPv6. For this reason, IPv6 was delivered with migration techniques to cover every conceivable IPv4 upgrade case. However, many were ultimately rejected by the technology community.
Currently, there are three main approaches:
Dual stack
6to4 tunneling
NAT-PT, ISATAP tunneling, and Teredo tunneling (last resort methods)
Some of these approaches are discussed in more detail later in the chapter.
The current advice for transitioning to IPv6 is "Dual stack where you can, tunnel where you must!"

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