While no one predicted a "Mad Max"-style apocalyptic catastrophe, experts at FutureNet this week nonetheless said that Internet architecture will face stiff challenges over the next few years that could put significant strain on the Web's effectiveness.

FutureNet is an annual conference held to address communications services from the perspectives of enterprises, ISPs and vendors. Its sponsor, Nemertes Research, made waves last year when it released a study that claimed that future Web growth would be slowed by inadequate investment in access-layer capacity. Additionally, the paper looked into other potential limits to Internet growth, including a lack of IP addresses and strains on routing tables. Both issues were hot topics of discussion at FutureNet, as panelists and speakers debated just how severe these challenges would be to Internet growth and what strategies ISPs and vendors should use to meet them.

One of the most immediate issues facing the Internet is the impending drought of IP addresses, which some forecasters have said could occur within the next few years. Ron Bonica, a consulting engineer on Juniper's routing-protocol software development team, said at FutureNet that while the actual exhaustion of IP addresses is likely further away than some had predicted, it is inevitable.

The reason for this coming IP address shortage is broadly recognized: IPv4, the first widely deployed version of Internet Protocol, which offers about 4.7 billion possible IP addresses, is running out of capacity to meet demand for new IP addresses. The situation has gotten so critical that this week Akinori Maemora, chairman of the Asia Pacific Network Information Centre (APNIC), labeled it a "crisis," while Tony Hain, IPv6 technical leader for Cisco, said that "most people in the world are still in a state of denial" about it.

Bonica said there are three realistic solutions to this problem, the first of which would be to stick with IPv4. While this would create some obvious immediate problems with the impending shortage of IP addresses, Bonica said that it would also lead to the creation of an IP address trading system by which companies and individuals who own an excess number of addresses could sell them at market value. The second possibility, said Bonica, would be a rapid universal deployment of IPv6, the IETF's next-generation Internet Protocol that can support several billion more addresses than IPv4. While Bonica said this was a possibility, he also said many organizations and companies have been reluctant to make the switch, since it would require a lot of investment on the part of end users and ISPs, and translation mechanisms to help make the switch aren't yet widely deployed.

Bonica predicted that we would see a compromise between these two solutions and that there would be a gradual progression from IPv4 to IPv6. Although he claimed to have "no crystal ball" in the matter, he said the gradual migration to the new standard made the most sense economically.

"One of these three paths will be chosen for economic reasons, and that will be the one that keeps people in business," he said.

The other big problem addressed at FutureNet was the potential strain that new IP addresses could put on routing tables, which are the master lists of network destinations stored in backbone routers that decide on the optimal paths between networks. During a panel session titled "The End of the Internet?" several industry experts said that the strain on routing tables was both a short- and long-term concern because routing tables are not scalable and don't adapt to exponential increases in IP addresses. As APNIC member Geoff Huston said years ago, "it's not the size of the table, but the number of updates per second that kills a router stone dead."