Novell LINUX ENTERPRISE SERVER 11 - ADMINISTRATION Administration Manual page 220

in the past fifteen years. Since Tim Berners-Lee at CERN (http://public.web
.cern.ch) invented the WWW in 1990, the number of Internet hosts has grown from
a few thousand to about a hundred million.
As mentioned, an IPv4 address consists of only 32 bits. Also, quite a few IP addresses
are lost—they cannot be used due to the way in which networks are organized. The
number of addresses available in your subnet is two to the power of the number of bits,
minus two. A subnetwork has, for example, 2, 6, or 14 addresses available. To connect
128 hosts to the Internet, for example, you need a subnetwork with 256 IP addresses,
from which only 254 are usable, because two IP addresses are needed for the structure
of the subnetwork itself: the broadcast and the base network address.
Under the current IPv4 protocol, DHCP or NAT (network address translation) are the
typical mechanisms used to circumvent the potential address shortage. Combined with
the convention to keep private and public address spaces separate, these methods can
certainly mitigate the shortage. The problem with them lies in their configuration, which
is a chore to set up and a burden to maintain. To set up a host in an IPv4 network, you
need a number of address items, such as the host's own IP address, the subnetmask, the
gateway address and maybe a name server address. All these items need to be known
and cannot be derived from somewhere else.
With IPv6, both the address shortage and the complicated configuration should be a
thing of the past. The following sections tell more about the improvements and benefits
brought by IPv6 and about the transition from the old protocol to the new one.
17.2.1 Advantages
The most important and most visible improvement brought by the new protocol is the
enormous expansion of the available address space. An IPv6 address is made up of 128
bit values instead of the traditional 32 bits. This provides for as many as several
quadrillion IP addresses.
However, IPv6 addresses are not only different from their predecessors with regard to
their length. They also have a different internal structure that may contain more specific
information about the systems and the networks to which they belong. More details
about this are found in Section 17.2.2, "Address Types and Structure" (page 208).
The following is a list of some other advantages of the new protocol:
206 Administration Guide