In BT Retail’s Carrier-Grade NAT pilot some customers will share IP addresses as an alternative to IPv6
BT Retail has begun testing a controversial technology called Carrier-Grade Network Address Translation (CGNAT), which will see some BT Retail customers sharing IP addresses, following a similar pilot scheme begun by BT-owned ISP PlusNet earlier this year.
The technology is being piloted with BT’s Option 1 Total Broadband customers, who BT says use the Internet the least.
Potential for disruption
“We believe they are the least likely group of customers to experience any issues or disruptions due to CGNAT, which can interfere with complex online activities like hosting servers at home,” BT said in a statement.
CGNAT is a response to the dwindling number of Internet Protocol (IP) addresses available under IPv4, the version of the protocol used across the vast majority of the Internet today. While IPv6, which offers many more IP addresses, has been defined for more than 20 years, a broad implementation of it across the Internet appears to be nowhere in sight, forcing service providers to explore techniques for keeping their IPv4 customers connected.
The technique has been criticised because it imposes certain limits on users by virtue of the fact that their broadband connection no longer has the use of a fixed unique IP address, but is rather sharing an address with other users – in BT’s trial, up to nine other users. This means, for instance, that users can’t serve content to the wider Internet from servers on their home network; and BT admits that it can also affect activities such as online gaming and dynamic DNS services.
Defending its trial, PlusNet pointed out that NAT is commonly used on LANs within homes and businesses, which mostly present one IP address to the wider Internet. Home routers use NAT, and BT has pointed out that NAT is also “standard practice” for mobile broadband providers, who have had to accommodate large numbers of new connected devices.
Critics, however, responded that mobile Internet services lack the flexibility that, until now, has been standard with ordinary broadband services.
‘Going against the open spirit of the Internet’
“(CGNAT) goes against the open spirit of the Internet and the principles which have generated such incredible innovation over the years,” said Axel Pawlik, managing director of the RIPE NCC, one of the Regional Internet Registries (RIR) that manage the allocation and registration of Internet number resources. “It is good that this is only a trial because that will give everyone a chance to evaluate the wider implications and whether there is any long-term benefit to CGNAT.”
The alternative to CGNAT is speeding up the rollout of IPv6, Pawlik argued, something BT said is unlikely to provide a solution to the IP address shortage anytime soon.
“BT is also working to introduce IPv6 internet addresses during 2013, but customers will need both IPv4 and IPv6 addresses for the foreseeable future,” BT stated.
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