Apologies if this has been posted elsewhere - i've been reading an article from BT stating their intention to close down the 20CN ADSL (up to 8mpbs) network from this year..

"The telecommunications giant plans to switch-off its 20th Century Network (20CN) at the end of next month, having gradually wound down its coverage over the past several years.

The network, which provides standard copper broadband speeds of up to 8Mbps, has been superseded and replaced by BT’s 20Mbps 21CN network in many places.

Businesses cannot operate these days without decent internet access, so this is something that needs attention straightaway.
At the moment, around 92 per cent of the UK is served by BT’s 21CN network, and in these areas its 8Mbps products will be withdrawn from 31 March.

In areas not covered by 21CN, BT has promised to maintain its legacy broadband network until the end of September 2014.

Read more: http://www.itpro.co.uk/networking/21...#ixzz34EnOAEvt "



My question is what happens in rural areas not covered by 21CN? BTs line states 20CN will be available in non 21CN areas until the end of September 2014 - there is however no mention of adding 21CN to these areas. I'ver had a look on SamKnows at a few exchanges and there are still a lot with no planned date for 21CN.

Anyone know whats been planned?

Doesn't make any sense to me at all I'm afraid.

This seems to imply that both 20CN and 21CN are only for carrying broadband access, which simply isn't true.

A very large percentage of BTs network still falls under the "20CN" moniker, although that network is slowly being wound down, but it will be a good few years yet before it is finally removed.

Even 21CN, which was originally envisiged as an entire network replacement for 20CN 10 or so years ago before being drasctically scaled back to an overlay network due to costs, is now being replaced by the next generation of network technology.

I got family friends 8 or 9 miles north of Falkirk and there Airth exchange is still only ADSL MAX and they can only get speeds of 6mb at best with AOL. They got Sky TV but Sky don't have there LLU at the exchange that's why they use AOL.
So if this is right will the likes of the Airth exchange that family friends are on have to get upgraded to up to 20mb speeds.
They said if fiber ever came to there exchange they would think of moving all back to BT to try and cut down on cost as they have seen the speeds I get with Infinity and the BT Youview service that I have. I think it will be years yet before there Airth exchange ever gets fiber.
Another family friend from the Falkirk area is on up to 20mb speeds only as fiber is not at there nearest BT green cabinet. Yet 4 or 5 streets away from them can get fiber at the nearest bt green cabinet to those streets.

Darren

21CN powers their ADSL2+/FTTC/P networks doesn't it? I was under the impression that they only stopped trying to push it as the PSTN replacement too, preferring instead to sweat the old network until things start to fall apart.

21CN was the push to Ethernet and IP instead of SONET and ATM and TDM. What's "the next generation" from that, apart from incremental upgrades? I work for a major BT 21CN supplier and there's not really anything revolutionary from us apart from upgraded hardware. They can buy bigger routers from us and do 100G instead of 10G, but nothing mind blowing.

I heard that the 20CN DSL network is only being closed down where 21CN already exists. They obviously won't and can't stop offering it on exchanges where there is no alternative, although I'd guess it might spur quicker upgrades.

Erm, is that article a tad misleading and alarmist?

BTw are withdrawing the IPStream and Datastream products this year.

Doesnt stop an ISP using IPStream connect for 20CN exchanges. BT have been telling ISPs for the past 2 years that any IPStream or Datastream products they sell, will have to be migrated over to to IPsC.

Also this year, BTw will be retiring IPsC on 21CN enabled exchanges. No point having a pile of old DSLAMs hanging around when much faster services are available.


As mentioned above.. BT have been warning ISPs for the past 2 yrs that this would be happening. Its their own fault if they havent switched to an alternative product by now.
In fact I cant think of any of the well known ISPs that are still using the old BT centrals.

ADSL2/HTTC/P are some of the services carried over 21CN, they aren't the reason for 21CNs existance.

When 12CN was first conceived, the original idea was to install a totally new network, and then migrate all of the traffic of the existing network, now called 20CN, and rip it all out.

Howver due to the sheer scale and cost of such a project 21CN was very quickly scaled down to an overlay network which would carry the traffic 20CN wasn't capable of carrying, such as IP and Ethernet.

So someone in, say, London calling their Auntie Mable in Leeds is still very likely to have their call routed via the 20CN PTSN. However the connection that same person uses for their broadband connection, or IPTV would be routed over 21CN.


To be 100% pedantic, BT use SDH not SONET, SONET is the ANSI standard. However the "next generation" is the move away from traditional TDM and SDH transport networks to a fully packet-switched T-MPLS network, as well as enhancing existing transport capacity by the use of "alien channels" over existing DWDM infrastructure. something BT have already trialled with the company I work for.

None of this 21CN is able to do in its existing form as imuch of it is still a TDM-based network.


20CN is going to be around in the core network long after is is removed from the local exchange access network, simply because it is money for old rope. It has long since paid for itself and, as long as it works, BT will keep using it.