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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  Internet Protocol (IP/IPv4, IPng/IPv6) and IP-Related Protocols (IP NAT, IPSec, Mobile IP)                 9  Internet Protocol Version 6 (IPv6) / IP Next Generation (IPng)                      9  IPv6 Overview, Changes and Transition

IPv6 Overview, Changes and Transition 1 2 3 Major Changes And Additions In IPv6

Design Goals of IPv6

The problem of addressing was the main motivation for creating IPv6. Unfortunately, this has caused many people to think that the address space expansion is the only change made in IP, which is definitely not the case. Since making a change to IP is such a big deal, it's something done rarely. It made sense to correct not just the addressing issue but to update the protocol in a number of other respects as well, to ensure its viability. In fact, even the addressing changes in IPv6 go far beyond just adding more bits to IP address fields.

Some of the most important goals in designing IPv6 include:

• Larger Address Space: This is what we discussed earlier. IPv6 had to provide more addresses for the growing Internet.
  
  
• Better Management of Address Space: It was desired that IPv6 not only include more addresses, but a more capable way of dividing the address space and using the bits in each address.
  
  
• Elimination of “Addressing Kludges”: Technologies like NAT are effectively “kludges” that make up for the lack of address space in IPv4. IPv6 eliminates the need for NAT and similar workarounds, allowing every TCP/IP device to have a public address.
  
  
• Easier TCP/IP Administration: The designers of IPv6 hoped to resolve some of the current labor-intensive requirements of IPv4, such as the need to configure IP addresses. Even though tools like DHCP eliminate the need to manually configure many hosts, it only partially solves the problem.
  
  
• Modern Design For Routing: In contrast to IPv4, which was designed before we all had any idea what the modern Internet would be like, IPv6 was created specifically for efficient routing in our current Internet, and with the flexibility for the future.
  
  
• Better Support For Multicasting: Multicasting was an option under IPv4 from the start, but support for it has been slow in coming.
  
  
• Better Support For Security: IPv4 was designed at a time when security wasn't much of an issue, because there were a relatively small number of networks on the internet, and their administrators often knew each other. Today, security on the public Internet is a big issue, and the future success of the Internet requires that security concerns be resolved.
  
  
• Better Support For Mobility: When IPv4 was created, there really was no concept of mobile IP devices. The problems associated with computers that move between networks led to the need for Mobile IP. IPv6 builds on Mobile IP and provides mobility support within IP itself.

At the same time that IPv6 was intended to address the issues above and many others with traditional IP, we should keep in mind that its changes are evolutionary, not revolutionary. During the many discussions in the IETF in the 1990s, there were some who said that while we were updating IP, perhaps we should make a complete, radical change to a new type of internetworking protocol completely. The end decision was not to do this, but to define a more capable version of the IP we've been using all along.

The reason for this is simple: IP, like our trusted older car, works. IPv6 represents an update that strives to add to the best characteristics of IPv4 rather than making everyone start over from scratch with something new and unproven. This design ensures that whatever pain may result from the change from IPv4 to IPv6 can be managed, and hopefully, minimized.

IPv6 Overview, Changes and Transition 1 2 3 Major Changes And Additions In IPv6