The internet industry is unprepared for the fundamental change in how it sends messages that will happen on New Year's Day 2009.
From the new year, the internet will use four-byte addresses (so-called 32-bit addresses), which means it can send messages to more than four billion discrete networks, compared with the 65,536 available with the current two-byte addresses, also known as Autonomous System (AS) numbers.
The change is essential to prevent the internet running out of address space as more networks connect to it. Not adapting to the change would be like leaving the city and postcode off a letter's address.
Geoff Huston, chief scientist at APNIC, the Regional Internet Registry for the Asia Pacific region, said he was deeply worried by the industry's lack of readiness.
"New entrants and networks that are expanding or merging will need new AS numbers, and as of 1 January 2009 these will be, by default, four-byte AS numbers," he said. "If router software and support systems in critical parts of the internet's infrastructure are not upgraded by January, we will encounter some significant network routing problems."
CIOs and network administrators will need to check that their network routers can cope. Although the new system should accommodate the old, there is a chance that some messages to and from older systems may not get through.
About 90% of the routers affected by the change are made by Cisco. Ian Foddering, systems engineer manager at Cisco UK, said a new version of its IOS software to accommodate the change was under test. "We are well aware of the timescale," he said, adding that the required functionality already existed in version IOS-XR 3.4, which has been available since September 2006.
Organisations affected are mostly telecommunications carriers, internet service providers, private network owners who switch messages to more than one other network, and outsourced network operators. Those with older routers may have to add more memory as well as upgrade their software, said Foddering.
Most internet users are unlikely to be affected because their network operator should have a change management plan in place for the upgrade.
"If you don't have an AS number, you don't need to worry about the change," said Malcolm Hutty, a spokesman for the London Internet Exchange. "But if you have outsourced your network, it's as well to check that your network provider is set up for the change. Otherwise, you'll find messages being dropped."
Andrew de la Haye, COO at RIPE NCC, which allocates AS numbers in Europe, said CIOs could check their routers by seeing whether the software specification was compatible with the longer four-byte AS numbers. "You can also run a quick test by configuring one of their four-byte peers," he said.
Organisations would need to ask their hardware vendor whether they offer four-byte AS number functions, said de la Haye. "If the hardware vendor is able to offer this, all that is required is a software update. However, if the hardware vendor does not support four-byte AS numbers, the CIO will need to replace the router, possibly from a new supplier."
Foddering said Cisco users could look up the Software Advisor on the Cisco website to see when the new software would be available and what other changes they would need to make.
A spokesman for ISPA, the UK's trade body for internet service providers, said, "We don't get involved in managing members' networks."
More about AS numbers and the looming change
An Autonomous System (AS) is a collection of networks or routers administered as a group sharing a common set of routing policies, each defined with a unique AS number. AS numbers are a vital part of the internet's core routing system, the Border Gateway Protocol (BGP).
Regional Internet Registries (RIRs) began allocating four-byte AS numbers by request in January 2007. From January 2009 they will allocate them by default.
There is a wiki with more on the operational implications of the change.
APNIC has set up a special website for vendors.
Network users can also contact RIPE NCC, which looks after internet resources for Europe, parts of Asia and the Middle East.