In the mid-1990's, the Internet
is a dramatically different network than when it was first established in the
early 1980's. Today, the Internet has entered the public consciousness as the
world's largest public data network, doubling in size every nine months. This
is reflected in the tremendous popularity of the World Wide Web (WWW), the
opportunities that businesses see in reaching customers from virtual
storefronts, and the emergence of new types and methods of doing business. It is
clear that expanding business and social awareness will continue to increase
public demand for access to resources on the Internet.
There is a direct relationship
between the value of the Internet and the number of sites connected to the
Internet. As the Internet grows, the value of each site's connection to the
Internet increases because it provides the organization with access to an ever
expanding user/customer
population.
Internet Scaling Problems
Over the past few years, the
Internet has experienced two major scaling issues as it has
struggled to provide continuous
and uninterrupted growth:
- The eventual exhaustion of the IPv4 address
space
- The ability to route traffic between the ever
increasing number of networks that comprise the Internet
The first problem is concerned with the eventual depletion
of the IP address space. The current version of IP, IP version 4 (IPv4),
defines a 32-bit address which means that there are only 232 (4,294,967,296) IPv4 addresses
available. This might seem like a large number of addresses, but as new markets
open and a significant portion of the world's population becomes candidates for
IP addresses, the finite number of IP addresses will eventually be exhausted.
The address shortage problem is
aggravated by the fact that portions of the IP address space have not been
efficiently allocated. Also, the traditional model of classful addressing does
not allow the address space to be used to its maximum potential. The Address
Lifetime Expectancy (ALE) Working Group of the IETF has expressed concerns that
if the current address allocation policies are not modified, the Internet will
experience a near to medium term exhaustion of its unallocated address pool. If
the Internet's address supply problem is not solved, new users may be unable to
connect to the global Internet!
Figure 1: Assigned and Allocated Network Numbers
The second problem is caused by
the rapid growth in the size of the Internet routing tables. Internet backbone
routers are required to maintain complete routing information for the Internet.
Over recent years, routing tables have experienced exponential growth as
increasing numbers of organizations connect to the Internet - in December 1990
there were 2,190 routes, in December 1992 there were 8,500 routes, and in
December 1995 there were 30,000+ routes.
Figure 2: Growth of Internet Routing Tables
Unfortunately, the routing
problem cannot be solved by simply installing more router memory and increasing
the size of the routing tables. Other factors related to the capacity problem
include the growing demand for CPU horsepower to compute routing table/topology
changes, the increasingly dynamic nature of WWW connections and their effect on
router forwarding caches, and the sheer volume of information that needs to be
managed by people and machines. If the number of entries in the global routing
table is allowed to increase without bounds, core routers will be forced to
drop routes and portions of the Internet will become unreachable!
The long term solution to these
problems can be found in the widespread deployment of IP Next Generation (IPng
or IPv6) towards the turn of the century. However, while the Internet community
waits for IPng, IPv4 will need to be patched and modified so that the Internet
can continue to provide the universal connectivity we have come to expect. This
patching process may cause a tremendous amount of pain and may alter some of
our fundamental concepts about the Internet.
