Content Overview IP version 6 (IPv6)
was developed to overcome the limitations of the current
standard, IP version 4 (IPv4). IPv4 allows end systems to
communicate and forms the foundation of the Internet as we know
it today. However, one of the major shortcomings of IPv4 is its
limited amount of address space. The explosion of new
IP-enabled devices and the growth of undeveloped regions have
fueled the need for more addresses. In the United States, the
Department of Defense (DoD) is a primary driver for the
adoption of IPv6. The other main market opportunities are the
National Research and Education Network (NREN), government
agencies, enterprises, service providers, home networking,
consumer appliances, distributed online gaming, and wireless
services. This module provides an overview of IPv6, IPv6
addressing and routing, OSPFv3, and IPv4 to IPv6 translation.
Content 8.1 Explaining IPv6 8.1.1
Introducing IPv6 The ability to scale networks for
future demands requires a limitless supply of IP addresses and
improved mobility. IP version 6 (IPv6) combines expanded
addressing with a more efficient and feature-rich header to
meet the demands for scalable networks in the future. IPv6
satisfies the increasingly complex requirements of hierarchical
addressing that IP version 4 (IPv4) does not provide. One key
benefit is that IPv6 can recreate end-to-end communications
without the need for Network Address Translation (NAT)—a
requirement for a new generation of shared-experience and
real-time applications. Cisco Systems currently supports IPv6
in Cisco IOS Software Release 12.2(2)T and later. The Internet
will be transformed after IPv6 fully replaces IPv4. However,
IPv4 is in no danger of disappearing overnight. Rather, it will
coexist with and then gradually be replaced by IPv6. This
change has already begun, particularly in Europe, Japan, and
Asia Pacific. These areas have been exhausting their allotted
IPv4 addresses, which makes IPv6 all the more attractive. In
addition to its technical and business potential, IPv6 offers a
virtually unlimited supply of IP addresses. IPv4 currently
provides approximately 2 billion usable addresses with its
32-bit address space. Because of IPv6’s generous 128-bit
address space, it can generate a virtually unlimited stock of
addresses—enough to allocate to everyone on the planet. As a
result, some countries, such as Japan, are aggressively
adopting IPv6. Others, such as those in the European Union,
are moving toward IPv6, and China is considering building pure
IPv6 networks from the ground up. Even in North America, where
Internet addresses are abundant, the U.S. Department of Defense
(DoD) mandated in October 1, 2003, that all new equipment
purchased must be IPv6-capable. The DoD intends to switch
entirely to IPv6 equipment by 2008. Web Links DoD
IPv6 article
http://www.networkworld.com/newsletters/isp/
2005/0110isp1.html
Content 8.1 Explaining
IPv6 8.1.2 IPv6 Features IPv6 is a powerful
enhancement to IPv4, and several IPv6 features offer functional
improvements: - Larger address space: Offers
improved global reachability and flexibility; the aggregation
of prefixes that are announced in routing tables; multihoming
to several Internet service providers (ISPs); autoconfiguration
that can include link-layer addresses in the address space;
plug-and-play options; public-to private readdressing end to
end without address translation; and simplified mechanisms for
address renumbering and modification.
- Simpler
header: Provides better routing efficiency; no broadcasts
and thus no potential threat of broadcast storms; no
requirement for processing checksums; simpler and more
efficient extension header mechanisms; and flow labels for
per-flow processing with no need to open the transport inner
packet to identify the various traffic flows.
-
Mobility and security: Ensures compliance with mobile IP
and IPsec standards functionality; mobility is built in, so any
IPv6 node can use it when necessary; and enables people to move
around in networks with mobile network devices—with many having
wireless connectivity.
Mobile IP is an Internet
Engineering Task Force (IETF) standard available for both IPv4
and IPv6. The standard enables mobile devices to move without
breaks in established network connections. Because IPv4 does
not automatically provide this kind of mobility, you must add
it with additional configurations.
IPsec is the IETF
standard for IP network security, available for both IPv4 and
IPv6. Although the functionalities are essentially identical in
both environments, IPsec is mandatory in IPv6. IPsec is enabled
on every IPv6 node and is available for use. The availability
of IPsec on all nodes makes the IPv6 Internet more secure.
IPsec also requires keys for each party, which implies a global
key deployment and distribution.
- Transition
richness: You can incorporate existing IPv4 capabilities in
IPv6 in the following ways:
- Configure a dual stack
with both IPv4 and IPv6 on the interface of a network
device.
- Use the technique IPv6 over IPv4 (also called
6to4 tunneling), which uses an IPv4 tunnel to carry IPv6
traffic. This method (RFC 3056) replaces IPv4-compatible
tunneling (RFC 2893). Cisco IOS Software Release 12.3(2)T (and
later) also allows protocol translation (NAT-PT) between IPv6
and IPv4. This translation allows direct communication between
hosts speaking different protocols.
Web Links IPv6 offers more than extra
addresses
http://searchnetworking.techtarget.com/
originalContent/0,289142,sid7_gci995047,00.html
Content
8.1 Explaining IPv6 8.1.3 Large
Address Space IPv6 increases the number of address bits by
a factor of four, from 32 to 128, which enables a very large
number of addressable nodes. However, as in any addressing
scheme, not all the addresses are used or available. Current
IPv4 protocol address use is extended by applying techniques
such as NAT and temporary address allocations. But the
manipulation of data payload by intermediate devices challenges
(or complicates) the advantages of peer-to-peer communication
and quality of service (QoS). IPv6 gives every user multiple
global addresses that can be used for a wide variety of
devices, including cell phones, personal digital assistants
(PDAs), and IP-enabled vehicles. These addresses are reachable
without using IP address translation, pooling, and temporary
allocation techniques. Increasing the number of bits for the
address also increases the IPv6 header size. Because each IP
header contains a source and destination address, the size of
the header field is 256 bits for IPv6, compared to 64 bits for
IPv4. Note
For more IETF information on IPv6
addressing details, refer to RFC 3513. Larger address spaces
make room for large address allocations to ISPs and
organizations. An ISP aggregates all the prefixes of its
customers into a single prefix and announces the single prefix
to the IPv6 Internet. The increased address space is sufficient
to allow organizations to define a single prefix for the entire
network. Aggregation of customer prefixes results in an
efficient and scalable routing table. Scalable routing is
necessary to expand broader adoption of network functions,
allowing the Internet to accommodate the following: -
Increased number of broadband consumers with high-speed,