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Standard User kitcat
(experienced) Fri 16-Oct-20 13:49:28
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Re: How are exchanges connected?


[re: Pheasant] [link to this post]
 
Pheasant

Many of the exchanges that will be bypassed are very small and the buildings are basically sheds. They are practically all leased and the rent is insignificant on these 1500..

With 5500 buildings in total and keeping 1000-1200 as head ends. Take off the 1500 'sheds' and you get 2800-3000 that actually reduce your costs. The sale and leaseback agreement was stacked with the highest rents on those hardest to get out of , ( except for a few that were high value like Chelsea, were there were lease breaks put with escalating rents to encourage BT to leave). There were also limits on how many BT could 'handback' in any period to protect the rental yield. There should be a end point to those but no idea when that would be, vaguely remember it was reported as a 30 or 40 year lease when signed..

So not a pot of gold to solve the pension issue .
Standard User Nick_W789
(regular) Mon 19-Oct-20 06:29:38
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Re: How are exchanges connected?


[re: witchunt] [link to this post]
 
I thought that these days, the PSTN was converted into VOIP at the earliest opportunity and all the switching was IP. I'd imagined that every exchange was now just racks of analogue terminal adaptors - are there still non-IP links between exchanges?
Standard User witchunt
(experienced) Mon 19-Oct-20 07:14:46
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Re: How are exchanges connected?


[re: Nick_W789] [link to this post]
 
That was the plan with 20CN but it didn't happen. Not entirely sure why, heard rumours they just could get it working back then . Then NGA became the focus and it all got shelved until the move from PSTN to VOIP over broadband.


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Standard User Pheasant
(member) Mon 19-Oct-20 09:01:00
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Re: How are exchanges connected?


[re: witchunt] [link to this post]
 
In reply to a post by witchunt:
That was the plan with 20CN but it didn't happen. Not entirely sure why, heard rumours they just could get it working back then . Then NGA became the focus and it all got shelved until the move from PSTN to VOIP over broadband.

Given conditions this year, are there still a significant number of exchanges left to convert under the 21CN programme? A December 2019 article on ispreview mentioned somewhere around 51 exchanges left on 20CN by this year.
Standard User chriswillsher
(newbie) Mon 19-Oct-20 17:27:27
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Re: How are exchanges connected?


[re: Pheasant] [link to this post]
 
I am struggling to find any information that can help me understand how fibre is going to be deployed in the UK if the objective of moving away from copper altogether is achieved. Whilst I am familiar with the exchange network that supports copper I have no idea what the future fibre network might look like. Are physical exchanges still required or will there be some form of computer controlled master distribution system? Presumably each fibre has a finite capacity and there must be aggregation points of some sort. I am in a rural area that is 100% EO. As we eventually get FTTP which is the current plan, does the existing exchange have a role in the future. Will the term connected to XYZ exchange have any meaning?
Where can I find a guide that might help me understand what the country's future communication network might physically look like even if I just concentrate on what Openreach is building.
Standard User Pheasant
(member) Mon 19-Oct-20 18:11:09
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Re: How are exchanges connected?


[re: chriswillsher] [link to this post]
 
https://www.youtube.com/watch?v=InjZDBBgkps
Standard User candlerb
(fountain of knowledge) Mon 19-Oct-20 18:50:53
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Re: How are exchanges connected?


[re: chriswillsher] [link to this post]
 
In reply to a post by chriswillsher:
Presumably each fibre has a finite capacity and there must be aggregation points of some sort.


The fibres are lit from larger, "head end" exchanges. That's where you'll find the Optical Line Termination (OLT) equipment that drives the fibres. Each OLT port drives one fibre, and each fibre can serve up to 32 properties.

Fibre cables carrying many fibres run from there to Fibre Aggregation nodes. Smaller cables run from those to Splitters, where the light from a single fibre is split up to 32 ways. Smaller cables again run from those run to Connectorised Block Terminals (CBTs), which is where the individual cables that connect to each house are connected.

In short, the FTTP network spans out as a tree from the head-end exchanges. It bypasses smaller exchanges.
Standard User Pheasant
(member) Mon 19-Oct-20 19:05:26
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Re: How are exchanges connected?


[re: chriswillsher] [link to this post]
 
In reply to a post by chriswillsher:
I am struggling to find any information that can help me understand how fibre is going to be deployed in the UK if the objective of moving away from copper altogether is achieved. Whilst I am familiar with the exchange network that supports copper I have no idea what the future fibre network might look like.

Are physical exchanges still required or will there be some form of computer controlled master distribution system?

Yes physical exchanges are still required, but there are fewer of these "head end" exchanges that serve larger geographic areas, rather than many exchanges serving smaller geographic areas. Smaller local exchanges play no role with FTTP.
In reply to a post by chriswillsher:
Presumably each fibre has a finite capacity and there must be aggregation points of some sort.

Optical fibre has tremendous information carrying capability, in the many terabits/sec for a single strand of glass.

However the architecture deployed for FTTP at least by Openreach, uses a passive optical network (PON) design that passively splits the optical fibre path in the journey from the exchange to the subscriber. The physical connection of a PON is thus "shared" amongst the users connected to it. It is not a dedicated 1-to-1 fibre connection from exchange to user.

The fibre network serving premises is indeed aggregated at various points on the fibres routes from the exchange, called unsurpringsly Aggregation Nodes. Up to 32 premises are served by each individual strand (or core) of fibre that terminates back on an equipment port in the head end exchange.
In reply to a post by chriswillsher:
I am in a rural area that is 100% EO. As we eventually get FTTP which is the current plan, does the existing exchange have a role in the future. Will the term connected to XYZ exchange have any meaning?

Your local rural exchange, unless it serves much larger area, will typically not be a head end exchange and will serve no role for FTTP.
You will still be connected to XYZ exchange, but that exchange may be 15 or 20 miles away, rather than 3 or 4 miles away.
In reply to a post by chriswillsher:
Where can I find a guide that might help me understand what the country's future communication network might physically look like even if I just concentrate on what Openreach is building.

Google is actually a good ally. Theres plenty of good information out there.
Standard User chriswillsher
(newbie) Mon 19-Oct-20 19:07:54
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Re: How are exchanges connected?


[re: candlerb] [link to this post]
 
Thanks for that helpful information. Will it be possible to know where the head-end exchanges are located in the same way that you can now map the copper exchange network?
I would like to try and get an idea of where the fibre cable to our village comes from and if possible, the route it will take. Currently we are being told that there is a section of duct that needs replacing but I have failed to find out where this might be.

We were in scope to be connected under the DSSB programme and already have the local infrastructure including an aggregation node in the manhole and CBTs on the poles but when they hit the blockage everything was cancelled. I am in the process of setting up a CFP and the initial cost indication is silly money for 40 properties. I understand that the initial figure is based on a robotic operation so am now awaiting a final cost which I believe involves some form of human sanity check.
Standard User Nick_W789
(regular) Mon 19-Oct-20 21:20:35
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Re: How are exchanges connected?


[re: chriswillsher] [link to this post]
 
In reply to a post by chriswillsher:
Thanks for that helpful information. Will it be possible to know where the head-end exchanges are located in the same way that you can now map the copper exchange network?

One trick is if there is any FTTP only near you (eg new build), to put one of those addresses in the BT Wholesale checker. It will say 'Connected to XXXXX exchange' - that is the fibre headend.
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