IPv6 Features
There's more to IPv6 than simply an expanded address space. IPv6 includes a
new header format, improved support for extensions and options, flow-labeling
capabilities, and authentication and privacy capabilities.
New header format. IPv6's new header format minimizes the overhead
often spent processing fields or information in packet headers. In IPv4, routers
and end systems are required to examine packets in detail, looking for information
necessary to determine whether the packet should be processed further. With
IPv6, you'll now find those fields (when required) after the main packet header
in Extension Headers. The new header format makes header processing much more
efficient at routers, which can ignore information in any Extension Headers—
with the exception of a Hop-by-Hop Extension Header, which must immediately
follow the IPv6 header. The Hop-by-Hop Extension Header might contain information
necessary for a router, such as a warning that a packet is a Jumbo packet (greater
than 65,535 bytes), or that a router must perform additional processing on the
packet.
Improved support for extensions and options. The change in the
IPv6 packet header format and the use of Extension Headers facilitate this new
feature. Options in Extension Headers have fewer limitations on size than in
IPv4, and IPv6 is extensible by adding more defined Extension Headers over time.
In IPv6, if a destination node receives an IPv6 packet containing an Extension
Header that it doesn't recognize, it informs the source node via Internet Control
Message Protocol version 6 (ICMPv6) that it can't process the packet. This feature
lets nodes implement IPv6 extensions independently of each other and still communicate.
Flow-labeling capabilities. IPv6 uses flow labeling for Quality
of Service (QoS). Flow labeling lets a source node define a priority (e.g.,
real time), which might be used in Voice over IP (VoIP) or video-over-IP solutions
to guarantee delivery of a packet within a certain time window. In IPv4, QoS
often requires a router or node to look beyond a packet's header for information.
In IPv6, all necessary information is in the header.
Authentication and privacy. IPv6's authentication and privacy
capabilities are, essentially, IPSec. IPSec is now a requirement in IPv6 implementations,
whereas in IPv4 it's an optional component. IPSec supports Authenticated Headers,
which authenticate nodes to each other and ensure the integrity of data exchanged
between them, and Encapsulating Security Payload (ESP), which has similar functionality
but also includes the ability to encrypt data for confidentiality.
Unlike IPv4, in which different implementations of the protocol by different
vendors could—and would—result in an inability of nodes to communicate
with each other, in IPv6 interoperability is almost guaranteed, thanks to the
underlying standards.
Stay Tuned
We've only just started. Now that you've got some solid foundational knowledge
about IPv6, you're primed to dive into the actual installation and use of the
protocol. Get ready to make it work on Windows 2003 and XP, and prepare yourself
for configuring interfaces with addresses and enabling DNS resolution. In a
later article, I'll also describe talk about enabling IPv6 and IPv4 interoperability
on your way to an all-IPv6 network.
| FUN FACTS
- There are enough available IPv6 addresses to give every star in the
known universe almost 7 x 1015 addresses.
- IPv6 was once called IPng, for Internet Protocol next generation.
- The successor to IPv4 couldn't be called IPv5 because the protocol
version 5 was allocated to the Internet Stream Protocol in the 1970s.
IPv6 reflects that the protocol is version 6.
- IPv4 uses 32 bits for addresses, whereas IPv6 uses 128 bits. There
aren't enough available IPv4 addresses for everyone on Earth, but with
IPv6, every person could have almost 5 x 1028 addresses each!
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