Introduction
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!
Networks (in thousands)
Class A
Class B
0
10
20
30
40
50
60
70
1983
1985
1987
1989
1991
1993
1995
Class C
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.
0
5
10
15
20
25
30
35
1990
1991
1992
1993
1994
1995
Routing Table Entries
(in thousands)
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.
