I’d like to talk about BT’s 21CN.
Good for you. What would you like to talk about?

I’d like to know what it is, for a start.
It’s a good question – BT’s 21CN is just shorthand for BT’s 21st Century Network.

So what’s so 21st century about it? All sounds a little sci-fi to me.
It’s the largest overhaul of BT’s core network to date – instead of using traditional PSTN (pubic switched telephone network) lines to shunt traffic across the network, it’s switching to a single, all-IP (internet protocol) network instead, which will carry all of its customers’ voice and data traffic.

What’s in it for BT then?
Unsurprisingly, BT is hoping for cost savings from its endeavours. The whole 21CN project will cost the telco in the region of £10bn to finish off and it hopes to save around £1bn a year as a result. It’s also one way for BT to jump on the VoIP trend, which is giving its traditional fixed-voice revenues a kicking, and avoid becoming just another transport pipe, instead making itself into more of a services company.

When will it all be done?
The deadline for completion has been something of a moveable feast. The telco had been ‘giving it large’ about the ambitious project, saying almost all customers will be on the 21CN by the end of the decade but that timeline has since slipped and BT is now saying 2011 looks likely to see the end of the project.

Will I notice any changes when it happens?
BT is saying very much not – ISP and corporate customers will be alerted to the change with a mailing but ‘the little people’ won’t be contacted individually, although there will be a publicity campaign around the changeover. BT says users shouldn’t notice any difference post-switch but will experience short outages, although these will be scheduled for when users are most likely to be asleep. The first customers to be switched over to the 21CN are located in Cardiff and should be moved across this month. BT hopes the Cardiff area will be all-IP within the next 12 months, while the bulk of the upgrading for the rest of the UK will take place from 2008.

You what…?

Bust through tech jargon with silicon.com’s Cheat Sheets.

Is it just replacing one type of network with another – like, will I get any new services?
Apparently so. Given the rollout won’t be finished for another five years, it’s difficult to predict just what those services will be, but BT reckons convergence will play a big part – sharing content and services across all manner of devices using the 21CN, for example. And with all that spare bandwidth hopefully sloshing around, technologies such as IPTV should progressively become the norm.

So we’re all going to get a shiny new network – has it been universally popular?
Not so much. Cable & Wireless’ CEO has criticised BT over the project, saying it’s working against its customers, while others have slammed its plans for the next generation of high-speed services: BT is leaning towards a plan of ADSL2+ for broadband in the future. ADSL2+ promises speeds of 24Mbps, tops – which won’t look so very high speed by 2011.

Marconi also put the boot in, questioning whether BT will be able to keep the rollout on track. However, Marconi did fail to win a contract to act as a supplier for the 21CN, and saw its share price nosedive accordingly back in early 2005. Alcatel, Ciena, Cisco, Ericsson, Fujitsu, Huawei, Lucent and Siemens all made the procurement cut.

So is it just BT doing this?
In short, no. Many other telcos are preparing or starting to roll out their own next-generation networks, although none are quite so far down the line. As BT’s CTO Matt Bross said last year: “If you look at the 21CN, all of the elements that we are doing can be seen in other domains. We are just bringing them together in the UK to make one end-to-end product. We will collect these from the multiple service networks. There are examples of this but not at this scale.”