This is a myth

i don't know who started it

i've heard it a few times now.

I don't think I am. Others perhaps. Re your earlier question as to what the OP means, I would have thought he means the BT Wholesale core.

You seem to be trying to say every provider uses BT core. To me, Vodafone uses ex-C & W to a large extent, and other services which may or may not be BT Group owned where they do not have a close enough POP on their own core.

Linking from the exchange to their own core even using BT cabling belonging to any division is not "BT core network". It is simply dark fibre available to rent.

Rogan8

BT's core network for BB has not been SDH for some years. WDM running ethernet at 10G/40G/100G per wavelength. There is still SDH for the TDM private circuit products and voice ccts but the last (3+) iterations for Data have been Ethernet.

In reply to a post by RobertoS:

I don't think I am. Others perhaps. Re your earlier question as to what the OP means, I would have thought he means the BT Wholesale core.

You seem to be trying to say every provider uses BT core. To me, Vodafone uses ex-C & W to a large extent, and other services which may or may not be BT Group owned where they do not have a close enough POP on their own core.

Linking from the exchange to their own core even using BT cabling belonging to any division is not "BT core network". It is simply dark fibre available to rent.

It isn't! Honestly you're wrong on some aspects and I do this stuff for my job. The dark fibre product launches next year. Dark fibre is NOT available from any part of BT Group right now.

I'm not saying every provider uses the BT core. That just isn't what I'm saying at all.

Re-reading the question I think you're right and he's asking about the BT Wholesale core network actually. So some of what I've written is in retrospect a bit irrelevant. But still, the fact people think Virgin Media run fibre into "most BT" exchanges for Sky is interesting.

Edited by deleted (Sat 22-Oct-16 15:04:00)

Roberto / Icarus
I think people need to define what they mean by Core network.

To me ( & I think Roberto) the following apply

Customer to local exchange is : Access network ( BTOR)
Local exchange to first router (Metro node or CP equivelent) is backhaul. ( BTOR, C&W, Virgin etc)
Between routers and Internet peer sites is Core network. BT TSO & CPs

Messy point is the Backhaul where CPs ( and BT divisions ) can buy products from both OR and BTW depending on whether they are bandwidth or dedicated circuits.

I agree with you quite a few providers have their own core, but only a few have any amount of non BT backhaul ( Virgin & Vodafone [C&W] ) outside the biggest cities.

Yes, the question was vague, and what non-BT Wholesale providers use is a side-issue anyway.

By "dark fibre" I am quite possible using the wrong term. I simply mean anything that is unused capacity - and by unused I mean not attracting rental revenue but just buried somewhere as part of a bundle in a trunk network. Waiting for someone/anyone to rent it and get linked to it.

I don't see trunk networking as such as being the same as core network.

For instance, Colossus (IIRC) was BT Wholesales "core network" from exchanges to ISP's Centrals. It still presumably wasn't physically theirs.

I think the OP is savvy enough that if he meant wider than the replacement for that, i.e. an Openreach core, he wouldn't have said BT. I also think if referring to BT Consumer or Business he would have said so. Which leaves BTW.

In turn leaving us with the question does he mean the capacity they have, or the physical installation and maintenance of it? What about the kit at the ends of the fibres?

There isn't anything available that reflects what you're describing there. Dark fibre is just unlit fibre. It's explained on that page I linked to pretty well and at present is not available.

You basically cannot bring your own fibre into a BT building at the moment and terminate it on your own equipment. You have to rent the last bit of the fibre (at a minimum) and it must link on to a bit of Openreach (ADVA) equipment where it can be tested if need be etc. In other words it is always "lit".

Where things will change next year is that providers can rent actual unlit dark fibre which no part of BT Group will have any dealings with other than if it is physically damaged and needs repairing.

I agree with you quite a few providers have their own core, but only a few have any amount of non BT backhaul ( Virgin & Vodafone [C&W] ) outside the biggest cities.

Yeah this bit is crucial, you only have to have a walk around a BT exchange in many large towns and you'll be surprised to find you'll only see BT jointbox (manhole) covers.

Edited by deleted (Sat 22-Oct-16 16:00:34)

Roberto

BT TSO are responsible for ALL the Core electronics including the WDM and Optics that runs over the fibres on CORE fibres. This includes all the Core Routers and other boxes that comprise a core network. BT TSO deal with all capacity issues in this space.

( DNS, BRAs and other boxes can be owned by other divisions as they relate to their customers but all BT ones will be located within the same Core nodes as the rest of the network.)

Access fibres and electronics are ALL BT OR.

Backhaul between exchanges is also BT OR responsibility BUT BT TSO usually look after the electronics on their behalf. ( Yes this can be in the same cables as the Core!). This was all setup in the original (2005) undertakings that split BT OR from the rest of BT and can be very confusing! ( Instide BT asd well as outside BT).

BT Wholesale's core run over logical bearers within the overall TSO Core. These can be VLANs or whole wavelengths making up a logically seperate network . BT Retail, BT Business and CPs and managed customers can also rent capacity on the core network to make up parts or all of their own core.

CPs handover points are (usually) in Manholes outside major exchanges (ISI: in span interconnect)) where each operator splices their fibres to BT fibres to enter the exchange, the Electronics are mutually agreed ( Identical) on both ends each owned and run by BT and the CP. Where there is LLU equipment within the exchange this still applies! But many operators rent capacity back to a larger ( ISI) exchange rather than pay to build fibre to that many exchanges.

Sometime in the next year BT will have to offer to supply dark fibre to other operators.
The terms are still unclear to me as this may involve just splicing fibres to make sections from CP site A to CP site B available and they will supply all electronics. Otherwise the CP will have to rent space, power & vent in BT exchanges to fit their own equipment and pay charges for this.

Where the equipment is LLU this already exists at one end but at some point the fibre will still need to be spliced to the CPs fibre.

Faulting then becomes a nightmare for BT as they have no vision of the service but I would lay money the CPs will always report a fault to BT first before looking at their own equipment. ( Always have done as it is easy to blame BT). All BT's electronics are connected to a managment network for reporting that allows faulting from both ends and remote management access, this allows 'guesses' at how far the break is in a 'cut fibre' incident, this ability is unlikely for many CPs.

That looks quite comprehensive, and thanks. Too much to take in all at one go while salivating at the smells emanating from the kitchen on a Saturday night .

Working out how that answers the OP's question is for another day, but your detail even more shows we need to know what was meant it.

I still don't think it answers the Vodafone point. A link from inside the exchange to any non-BT supplier with fibre arriving in a manhole outside that exchange is not BT core. I accepted a while ago that my understanding of what dark fibre is was incorrect.

It remains the case that what I said before is true - that non-BT fibre owned by Vodafone and linked from the exchange in a manhole outside the exchange, going all the way from there to their own routers/services, is not running over BT core. "However someone like Sky, TalkTalk, Voda, Zen etc who want their own backhaul would used the EBD product from Openreach directly" is not true about Vodafone other than if the link from the exchange to outside is an EBD product. If it is, it still isn't "core".

If every BT fibre is core, then none are.

In reply to a post by RobertoS:

"However someone like Sky, TalkTalk, Voda, Zen etc who want their own backhaul would used the EBD product from Openreach directly" is not true about Vodafone other than if the link from the exchange to outside is an EBD product. If it is, it still isn't "core".

If every BT fibre is core, then none are.

Well we are both right. If you think about it the likes of Vodafone and Sky won't have their own fibre networks running to a manhole right outside the BT exchange in MOST places. Larger towns and cities, maybe. But most places, no.

I'm stood outside/inside an exchange right now. It has LLU services from most providers. Certainly Voda, TalkTalk and Sky. But none of them have a core network nearby that they could extend to the exchange. So ALL of them will be renting backhaul.

Hopefully I'm being a little bit clearer, the explanation given by the poster above is fantastic and should answer most of your questions though.