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[Weaver]

See https://www.samknows.com/broadband/exchanges/21cn_overview

Is this article accurate? It's very out-of-date seemingly. Probably can't be helped.

Did things turn out as described?

[gt94sss2]

You are right - the article is very out of date.

The 21CN Network has continued to rollout on the data side - hence WBC exchanges etc but BT basically scrapped the voice side of their 21CN Network rollout.

[Weaver]

I thought so, re voice.

Is it that BT has decided it's too much work for no reward, and it ain't broke?

[gt94sss2]

Others may know more but I think they ran into several problems on the voice side including:

- cost;
- problems with the new technology;
- difficulties trying to run migrate existing services to 21cn;
- dragging the rest of the industry with them; and
- the fact that all anyone else was concerned about was data

Personally, I suspect BT still have longer term plans to switch voice to IP and close lots of smaller exchanges etc - and you can see that by the way they roll out VDSL by using larger exchanges to cover cabinets in smaller smaller exchanges..

[Weaver]

> Personally, I suspect BT still have longer term plans to switch voice to IP

I suppose you have to be right. There will come a time when the older hardware will start to become a pain, won't there?

> and close lots of smaller exchanges etc

Why so? They have to terminate links somewhere and have POPs close to where they're needed?

[Weaver]

Your point about dragging the rest of the industry with them is an important one. What on earth do you do when other networking companies still have the old systems and you have to interwork with them?

[gt94sss2]

> and close lots of smaller exchanges etc

Why so? They have to terminate links somewhere and have POPs close to where they're needed?

BT already flog off old exchange buildings (or parts of them) for development/housing as digital equipment doesn't take the same space that older telephony equipment needed.

As you get fibre and DSLAMS further into the access network, the need for local exchanges lessens - especially if you are using voip - and traffic can the be sent to fewer larger exchanges around the country instead - leading to the network being easier to manage centrally and cost savings from not having to maintain so many buildings (or from selling them)..

[Weaver]

I would have assumed that it is expensive to reroute fibre to get round the loss of an exchange?

[gt94sss2]

I assume its cheaper in the long run than maintaining extra exchange buildings/equipment

[Weaver]

If you have a load of copper and fibre converging on an exchange, how do you make it all go away if you want to cash in and turn the exchange into residential housing?

[gt94sss2]

If you have a load of copper and fibre converging on an exchange, how do you make it all go away if you want to cash in and turn the exchange into residential housing?

I haven't been actively involved in telecoms for a while but as an example you can just look at how Openreach are implementing the rollout of FTTP/VDSL.

Many small exchanges are not being enabled themselves, but their cabinets/fibre nodes are connected to headends at larger exchanges. This means these smaller exchanges can be 'bypassed' in the long term.

The fibre infrastructure feeding the VDSL network has spare fibres ready to support an eventual GPON FTTH/G-fast rollout.

There will still issues to be resolved - for instance:

1) 999 services;
2) powering lines in a power cut;

but if/when BT switch to VoIP in the local access network and carry that traffic over fibre rather than copper than the smaller exchanges become less important/eventually redundant freeing up those locations.

As I said, I believe its a long term strategy.. its not going to happen quickly.

[aesmith]

As you get fibre and DSLAMS further into the access network, the need for local exchanges lessens - especially if you are using voip - and traffic can the be sent to fewer larger exchanges around the country instead - leading to the network being easier to manage centrally and cost savings from not having to maintain so many buildings (or from selling them)..

Realistically BT hasn't a hope in hell of getting rid of analogue PSTN in the medium term, so those copper cables converging on the exchange will need to remain in place.  Presumably if the exchange goes altogether it's replaced by a bit junction box and multipair cable to the designated larger exchange.   A lot of these rural exchanges are only remote shelves in any case.

[Weaver]

So a huge underground access box (?) with manhole and a whole lot of fibre coming in and out. And the battery supply thing isn't solved. My cousins still have an actual big electro-mechanical GPO bell, a clanger, on the wall in the kitchen.

[NewtronStar]

Having your PSTN line number connected to local exchange and FTTC coming from the larger exchange has one advantage the phone & broadband won't go down at the same time if there is a fault at one exchange.

The disadvantages with a headend fttc exchange and local pstn exchange is that your available xDSL services is locked to your local exchange even if the headend exchange has 21CN and LLU'd for example I can't get llu'd fttc with TalkTalk yet other who's pstn line number is connected to the larger exchange can 

[Weaver]

@NewtronStar apol I am being dim.