The second problem is caused by the rapid growth in the size of the

Internet routing tables. Internet backbone routers are required to main 

tain complete routing information for the Internet. Over recent years,

routing tables have experienced exponential growth as increasing num 

bers of organizations connect to the Internet. In December 1990 there

were 2,190 routes, in December 1995 there were more than 30,000

routes, and in December 2000 more than 100,000 routes. 

F I G U R E   2 .   G ro w t h   o f   I n t e r n e t   R o u t i n g   Ta b l e s

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 grow 

ing 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 infor 

mation that needs to be managed by people and machines. If the num 

ber 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 wide 

spread deployment of IP Next Generation (IPng or IPv6). Currently,

IPv6 is being tested and implemented on the 6Bone network, which is

an informal collaborative project covering North America, Europe, and

Japan. 6Bone supports the routing of IPv6 packets, since that function

has not yet been integrated into many production routers. Until IPv6

can be deployed worldwide, IPv4 patches will need to be used and

modified to continue to provide the universal connectivity users have

come to expect.

U N D E R S TA N D I N G   I P   A D D R E S S I N G

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