Stateless autoconfiguration: IPv6 defines both a stateful and a stateless
address autoconfiguration mechanism. The stateless autoconfiguration requires no
manual configuration of hosts, minimal configuration of routers, and no
additional servers. The stateless mechanism allows a host to generate its own
addresses using a combination of locally available information and information
advertised by routers. Routers advertise prefixes that identify the subnet(s)
associated with a link, while hosts generate an "interface identifier" that
uniquely identifies an interface on a subnet. Combining the two yields an
address. In the absence of routers, a host can only generate link-local
addresses. However, link-local addresses are sufficient to allow communication
among nodes attached to the same link [15].
2.3 Routing
Routing in IPv4 is much the same as in IPv6 but the addresses are 128-bit
instead of 32-bit addresses in IPv4. The routing algorithms (OSPF - The Open
Shortest Path First, RIP - Routing Information Protocol, IDRP – Inter Domain
Routing Protocol, ISIS - Intermediate System-Intermediate System, etc.) of IPv4
can be used to route IPv6.
To support new routing functionality, IPv6 includes routing extension, which
includes [6]:
-
provider selection
-
host mobility
-
auto-readdressing
2.4 NAT and large address space
The Network Address Translation (NAT) is used in the current IPv4 Internet
protocol to expand the number of addresses. NAT [3] was a short-term solution to
IPV4 address depletion, and it presents a number of problems. NAT destroys a key
benefit of end-to-end connectivity through the network. Because of the
widespread usage of NAT in IPv4 networks, it is impossible to deploy end-to–end
security mechanisms.
In the IPv6 network with its availability of a large number of addresses for all
IP devices, there is no need for translating hundreds of Internal IP addresses
into a few global IP addresses. NAT also presents a challenge for many
applications such as IPSec (Security Protocol) and applications requiring
quality of service (QoS) such as voice over IP (VoIP). With the IPv6 protocol,
NATs are no longer necessary.
In IPv4 networks, the shortage of address space causes widespread usage of NAT.
With large address space in the IPv6 network it is possible to deploy superior
end-to-end data security mechanisms by eliminating the need for NAT.
2.5 Security
IPv6 has been designed to satisfy the growing and expanded need for network
security [3]. The first mechanism is the IP authentication Header [8], and the
second mechanism is the IP Encapsulating Security Payload [9].
