Stanford University's ongoing effort to conserve Internet address space by renumbering its campus network highlights two of the Internet engineering community's most hotly debated questions:
Exactly how severe is the shortage of Internet addresses? And are short-term measures being ignored that might help stretch the supply until the next version of IP- IPv6 - provides a wealth of new addresses?
In April, Stanford will complete a labor-intensive two-year effort that involves reconfiguring all 56,000 computers and devices on its network to more efficiently use Internet address space. Afterward, Stanford will return an enormous block of unused Internet addresses - more than 16 million - to the organization that oversees 'Net address allocation in North America.
"In the early days, when there was address space galore, people weren't thinking that the Internet would turn into such a phenomenon," says Jay Kohn, assistant director of networking systems at Stanford. "But as members of the network community, we need to think about this issue and do the right thing. . . . It's important for people that have large address space like ours to be good network neighbors."
Although hailed as noble, some see Stanford's network re-engineering effort as more of a symbolic gesture than a real-world solution to the Internet address dilemma.
"Stanford's move is gracious and commendable, but it represents about 0.5% of the address space," says Christian Huitema, chief scientist in Telcordia Technologies' Internet Architecture Research Laboratory. Huitema asserts that for all practical purposes, the Internet community ran out of addresses in 1992, when the registries started clamping down on requests for space. "It would take many such moves" to make much of a difference, he adds.
Stanford's efforts are "only a marginal solution to the problem," says Brian Carpenter, chair of the Internet Architecture Board and program director for 'Net standards and technology at IBM. "The move delays running out of Internet addresses by so many days or weeks or months, but it's not a fundamental fix."
Nonetheless, some observers say that encouraging organizations with large blocks of unused Internet address space - such as Stanford, the Massachusetts Institute of Technology, Michigan State University, Xerox and Lucent - to return unused portions is a sensible short-term strategy.
"One solution is for people to voluntarily return address space if they don't have a requirement for it," says Kim Hubbard, president of the American Registry for Internet Numbers (ARIN). "It's expensive to renumber your network, but Stanford is doing that right now. . . . Some organizations are willing to make the effort."
How best to allocate precious Internet address space has been debated for years, but the issue flared up again last month when a simple question about how much address space is left sparked an exchange of hundreds of e-mails on the Internet Engineering Task Force's (IETF) electronic mailing list.
The debate stems from the fact that the current version of IP - IPv4 - uses 32-bit addresses. This means IPv4 can theoretically accommodate four billion addresses. But because of IPv4 design shortcomings and limits in the routing tables, only a fraction of possible IPv4 addresses can actually be used. Estimates of how many addresses IPv4 can handle range from 150 million to one billion.
"People have to realize that the four billion addresses that IPv4 officially provides doesn't mean you can run four billion computers on the Internet," Carpenter says. "My belief is that it is very, very hard to push the density above about 160 million addresses."
Currently, a little more than half of all possible IPv4 addresses - or two billion addresses - have been assigned to ISPs, corporations and government agencies. But only an estimated 69 million addresses are actually in use.
Even though there are millions of unused IPv4 addresses, the Internet registries have strict conservation policies that make it difficult for corporations to justify receiving sizable blocks of address space. The registries have restrictive policies in place as they await the deployment of IPv6. With its 128-bit addresses, IPv6 provides a virtually infinite number of addresses.
"I think the situation has gotten better than it was a few years ago" because of the registries' conservation policies, ARIN's Hubbard says. "There was a point where we were concerned that we would run out of space before IPv6 was available. That's why we created policies to slow down the rate of allocations."
Until IPv6 rolls out over the next few years, Internet policymakers are stuck in the awkward position of bemoaning the shortage of 'Net addresses while sitting on a huge stockpile of unassigned numbers. But they worry space will quickly run out if they liberalize allocation policies.
"For new companies trying to get on the Internet, the address shortage is real," Carpenter says. "ISPs will only give out a block of 16 addresses or so to new customers." This situation forces companies to use network address translation, a technique for supporting multiple private Internet addresses with a single public Internet address, to cope with their meager allotments.
Many big U.S. firms, however, have more than enough addresses. "The large companies and universities all got their address space years ago when the policies were much less conservative," Carpenter says. "We're not hurting yet."
Stanford is one of the organizations with an abundance of address space, including a Class A block of 16 million Internet addresses and four Class B blocks, each of which supports more than 65,000 addresses (see story, page 104). Stanford is migrating all the computers on its network to the Class B space and will return the Class A block to ARIN.
"We certainly didn't need the Class A block," says Ron Roberts, architect and operations manager for the Stanford University Network (SUNet). "While it was prestigious and emblematic of Stanford's early involvement with the Internet, there was no way to really make a case for it. . . . In the spirit of good Internet citizenship, we're relinquishing our squatter's right to Class A."
Stanford's network services staff had to convince university leaders that renumbering the network was the right thing to do. Then the staff embarked on a mission to educate the university's user community about making the change. This was a challenge because the SUNet team doesn't manage the hosts on the university's local networks, only the backbone routers and network devices. So they had to teach LAN administrators and end users how to reconfigure the Internet addresses on their machines. For users who had not yet adopted the Dynamic Host Configuration Protocol, this task was particularly time-consuming.
DHCP obtains IP addresses, when needed, for clients from local servers.
So far, about 20,000 of the university's systems have been renumbered, and the rest will be done by April 30.
"It's a lot of work," Stanford's Kohn admits. "But it's doable work. You have to be very organized and very planned. . . . It's gone well, I think."
In the mid-1990s, several other Class A holders - including Computer Sciences Corp., Electronic Data Systems and the U.S. Department of Defense - returned some of their unused Internet address space. Stanford, however, is the first organization to return an entire Class A block. Many observers say Stanford's gesture is likely to put pressure on the holdouts.
"We don't have any plans to renumber our network," says Richard Moore, division manager for network services at Michigan State University. Moore says the university is using a fraction of the Class A space that was originally allocated to Merit, a consortium of Michigan universities and colleges.
The other Merit members have renumbered their networks and migrated to Class B address space. "Why should we put our users and staff through all that bloody change?" Moore says. "With the latest router technology, I think they could just assign numbers around our space."
Jeffrey Schiller, network manager at MIT and a member of the IETF leadership, says he has no plans to renumber the 80,000 machines on the university's network.
"There is not an address shortage," Schiller says. "There's an artificial shortage because the registries are being very stingy about giving out addresses."
Schiller says that MIT doesn't want to spend the money to renumber its network, particularly if the arrival of IPv6 will make the effort meaningless.
"We keep our eye on the amount of space that's being allocated," Schiller says. "If there is a real shortage of address space, we'll see it coming. . . . Then we'll incrementally move to part of our Class A space. But we're not going to do it pre-emptively because we don't see the need."
Ironically, even Stanford officials question whether their Class A space is needed immediately.
"I'm not personally one of those people who thinks there's an IPv4 address shortage," Kohn admits. "I think our efforts will make a difference, but I don't think there's a crisis."
Current statistics on IPv4 address assignments and usage