IPv6 is one of the most significant network and technology upgrades in history. It will slowly grow into your existing IPv4 infrastructure and positively impact your network. Reading this book will prepare you for the next step of networking technology evolution. IPv6 product development and implementation efforts are already underway all over the world. IPv6 is designed as an evolutionary step from IPv4. It is a natural increment to IPv4, can be installed as a normal software upgrade in most Internet devices, and is interoperable with the current IPv4. IPv6 is designed to run well on high performance networks like Gigabit Ethernet, ATM, and others, as well as low bandwidth networks (e.g., wireless). In addition, it provides a platform for new Internet functionality that will be required in the near future, such as extended addressing, better security, and quality of service (QoS) features.
IPv6 includes transition and interoperability mechanisms that are designed to allow users to adopt and deploy IPv6 step by step as needed and to provide direct interoperability between IPv4 and IPv6 hosts. The transition to a new version of the Internet Protocol (IP) must be incremental, with few or no critical interdependencies, if it is to succeed. The IPv6 transition allows users to upgrade their hosts to IPv6 and network operators to deploy IPv6 in routers with very little coordination between the two groups.
The main changes from IPv4 to IPv6 can be summarized as follows:
- Expanded addressing capability and autoconfiguration mechanisms
The address size for IPv6 has been increased to 128 bits. This solves the problem of the limited address space of IPv4 and offers a deeper addressing hierarchy and simpler configuration. There will come a day when you will hardly remember how it felt to have only 32 bits in an IP address. Network administrators will love the autoconfiguration mechanisms built into the protocol. Multicast routing has been improved, with the multicast address being extended by a scope field. And a new address type has been introduced, called Anycast address, which can send a message to the nearest single member of a group.
- Simplification of the header format
The IPv6 header has a fixed length of 40 bytes. This actually accommodates only an 8-byte header plus two 16-byte IP addresses (source and destination address). Some fields of the IPv4 header have been removed or become optional. This way, packets can be handled faster with lower processing costs.
- Improved support for extensions and options
With IPv4, options were integrated into the basic IPv4 header. With IPv6, they are handled as Extension headers. Extension headers are optional and only inserted between the IPv6 header and the payload, if necessary. This way the IPv6 packet can be built very flexible and streamlined. Forwarding IPv6 packets is much more efficient. New options that will be defined in the future can be integrated easily.
- Extensions for authentication and privacy
Support for authentication, and extensions for data integrity and data confidentiality, have been specified and are inherent.
- Flow labeling capability
Packets belonging to the same traffic flow, requiring special handling or quality of service, can be labeled by the sender. Real-time service is an example where this would be used.
Tip
For a current list of the standardization status of IPv6, you can refer to http://playground.sun.com/pub/ipng/html/specs/standards.html.
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