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Author Topic: Future of ADSL EO lines  (Read 2063 times)

j0hn

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Re: Future of ADSL EO lines
« Reply #15 on: September 14, 2019, 12:00:28 PM »

Indeed.

I can't see OpenReach finding a feasible way to run reliable, streamlined line tests from DSLAMs from multiple vendors.

They have a working solution as the moment.
Easier to just leave E-Side recovery till copper is fully retired and recover the whole lot at once.
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ejs

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Re: Future of ADSL EO lines
« Reply #16 on: September 14, 2019, 01:17:30 PM »

I can't see any reason why Openreach couldn't do it if they wanted to. I don't think it would be wildly different than how the DLM interacts with different DSLAMs. There's the ITU-T G.996.2 document on line testing, which will be what the different vendors will have implemented. Currently quite a lot of the information returned in the GEA service test already comes from the DSLAM (or from the modem via the DSLAM).
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Weaver

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Re: Future of ADSL EO lines
« Reply #17 on: September 14, 2019, 08:16:54 PM »

Could someone clarify for me how BT might sell off eg the Broadford exchange? Wonít some physical locations for interconnects to aggregation links be needed somewhere?
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PhilipD

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Re: Future of ADSL EO lines
« Reply #18 on: September 15, 2019, 06:51:02 AM »

Hi

E-Side copper is likely to remain for SOGEA products, post PSTN shutdown.
The E-Side is necessary to run all line tests for xDSL based services.
That includes ADSL products, VDSL2 products and G.Fast.

I would expect the E-Side to remain until the D-Side is removed.
I've seen nothing to suggest otherwise and testing can't be done from the DSLAMs so I see no other way getting round that.

No E-Side, no ADSL so no tests required for that.  FTTC/G.Fast do their own testing from the cab, you can't test much about VDSL/G.Fast from the E-Side/Exchange when the data signal is injected at the cabinet, and filters stop the signal from back tracking into the E-Side. 

All you can do from the E-Side is check if PSTN is working, which checks the physical status of the line, and those tests are going to become irrelevant when there is no PSTN, plus finding a fault with such a test and sending an engineer out who finds an E-Side fault on the line, well that's a waste of time if nothing is being delivered from the exchange.

Regards

Phil
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PhilipD

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Re: Future of ADSL EO lines
« Reply #19 on: September 15, 2019, 07:02:19 AM »

Hi

Could someone clarify for me how BT might sell off eg the Broadford exchange? Wonít some physical locations for interconnects to aggregation links be needed somewhere?

I didn't say they would sell every exchange.

Fibre may not be delivered from your local exchange.  Local exchanges were only required because of the way the public switched telephone network works, and it made sense and was the only practical way to deliver a telephone service, by having local areas have their own exchange, plus the kit to make it work takes up a lot of space, or did originally when it was mechanical switches, so that kit had to be distributed across the UK local to where it "switched the calls" to that area.

With data and fibre, you don't need the physical space, and it can run for many miles back to a destination.  Think about Virgin Media or other data only suppliers, they've managed perfectly well without having "exchanges" in every town.

So when installing fibre for VDSL, and aggregation nodes for FTTP, BT choose certain exchanges to be a "point of presence" and the fibre terminates there, completely bypassing, in many cases, the local telephone exchange.

Therefore once the exchange is no longer supplying ADSL or PSTN services, it's doing nothing at all.  They just turn the lights off, rip the kit out for scrape value most likely, and put the land/building up for sale.

Regards

Phil



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ejs

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Re: Future of ADSL EO lines
« Reply #20 on: September 15, 2019, 07:08:10 AM »

Line testing to check the physical status of the line would still be needed. You'd still want to find things like a break in the network and its approximate location, so you could send someone out to fix it without having to book an appointment for a home visit. Otherwise you'd have situations with no sync, can't determine what or where the problem is, and would have to book a home visit appointment.
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gt94sss2

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Re: Future of ADSL EO lines
« Reply #21 on: September 15, 2019, 12:23:48 PM »

Itís likely that BT havenít owned the Broadford exchange for years.

BT sold most of their exchanges back in 2001: https://www.telegraph.co.uk/finance/2743456/Property-sale-to-cost-BT-40m-a-year.html

Itís now in the process of selling off 90% of its remaining property estate:

https://www.theguardian.com/business/2019/jun/05/bt-to-close-offices-in-more-than-270-uk-locations
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Weaver

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Re: Future of ADSL EO lines
« Reply #22 on: September 15, 2019, 01:14:22 PM »

Philip, I just assumed that fibre comes into say an exchange and then goes out again from there to the FTTC cabs ? And I assumed that you need some dry enclosed place to make the fibre-fibre interconnects or to park switches or L2 routers or whatever ? Where am I going wrong? I realise that I know nothing about the further upstream fibre-side topology of FTTx, upstream of the green cab.

If for example there is a link to another more important Ďnew POPí exchange from a minor local one, are we saying that all FTTC cabs would have new long fibre links to the new POP even though it is much much further away? Apologies for being stupid.
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RealAleMadrid

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Re: Future of ADSL EO lines
« Reply #23 on: September 15, 2019, 06:31:29 PM »

In many areas, not just rural locations, FTTC cabs connect to a head end exchange where the routers and switches are situated. The fibre links may not go anywhere near the local PSTN exchange. My head end exchange is about 12 miles away.
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Weaver

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Re: Future of ADSL EO lines
« Reply #24 on: September 16, 2019, 03:31:37 AM »

@RealAleMadrid Just to check my understanding; is it the case that when the FTTC cabs were put in in your area, the fibre feeds to them were originally put in running all the way direct to that PoP 12 miles away?

I was however talking about a case when this was not so originally; where hypothetically the PoP is at the nearest exchange anyway. But letís say BT wanted to completely get rid of that exchange ; what would happen then ? A costly rerouting or else just decide not to bother to do it at all, because of the costs involved ?
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j0hn

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Re: Future of ADSL EO lines
« Reply #25 on: September 16, 2019, 10:26:58 AM »

FTTC/G.Fast do their own testing from the cab, you can't test much about VDSL/G.Fast from the E-Side/Exchange when the data signal is injected at the cabinet, and filters stop the signal from back tracking into the E-Side. 

Not entirely correct.

Some of the current line tests are done from the TAM's in the exchange, for both G.Fast and VDSL2.

Are OpenReach connecting the E-Side on SOGEA lines for giggles?
What do you suppose the purpose of this is without PSTN?

Quote
you can't test much about VDSL/G.Fast from the E-Side/Exchange when the data signal is injected at the cabinet, and filters stop the signal from back tracking into the E-Side.

That doesn't prevent tests being carried out from the exchange TAM's kit.

MELT is a DC/narrowband line testing technique that supports the measurements of the electrical line properties at DC, such as resistance, shorts, opens, and capacitance.
MELT operates at DC and at frequencies below the xDSL spectrum, MELT testing can be performed without disrupting broadband services.

Proper testing requires DC coupling of the test circuitry to the line. Not possible on the DSLAM line card because it's AC coupled to the line via a line transformer.

Without sync DSLAM based line testing becomes pretty useless for some tests.

If the DSLAM already does all the VDSL2/G.Fast line tests I ask again why OpenReach are connecting the E-Side to SOGEA connections, on every single SOGEA install.
SOGEA is simply DSL without PSTN.
« Last Edit: September 16, 2019, 01:08:52 PM by j0hn »
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j0hn

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Re: Future of ADSL EO lines
« Reply #26 on: September 16, 2019, 11:04:11 AM »

@RealAleMadrid Just to check my understanding; is it the case that when the FTTC cabs were put in in your area, the fibre feeds to them were originally put in running all the way direct to that PoP 12 miles away?

I was however talking about a case when this was not so originally; where hypothetically the PoP is at the nearest exchange anyway. But letís say BT wanted to completely get rid of that exchange ; what would happen then ? A costly rerouting or else just decide not to bother to do it at all, because of the costs involved ?

They picked Head-End/Handover exchanges at the start of the NGA rollout.

Small exchanges that were handling ADSL/PSTN were left as they are.

The Fibre Head-end equipment (OLT/L2 switchas/etc) were installed in the NGA exchanges from day 1, with a future PSTN/DSL switch off in mind.

For those on smaller exchanges their line runs to the PCP/FTTC cabinet, then the E-Side (voice/ADSL) comes from the local small exchange but the fibre runs back to the Head-End.
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PhilipD

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Re: Future of ADSL EO lines
« Reply #27 on: September 16, 2019, 02:12:59 PM »

Not entirely correct.

Some of the current line tests are done from the TAM's in the exchange, for both G.Fast and VDSL2.

It sounds like they are simply using legacy tests and continue to do so for SOGEA.  There is little reason to have an E-Side though if nothing is supplied from the exchange when services are turned off, and it's going to be a very expensive test system if they keep it.  Part of the reason PSTN is being retired is the equipment is nearing end of life, but surely its the PSTN line cards that are doing the tests, are they really going to maintain all that equipment just to run a test on the odd telephone from the exchange?

Seems very short sighted if they haven't a plan to test from the DSLAM.

Regards

Phil


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PhilipD

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Re: Future of ADSL EO lines
« Reply #28 on: September 16, 2019, 02:22:05 PM »

Hi

Philip, I just assumed that fibre comes into say an exchange and then goes out again from there to the FTTC cabs ? And I assumed that you need some dry enclosed place to make the fibre-fibre interconnects or to park switches or L2 routers or whatever ? Where am I going wrong? I realise that I know nothing about the further upstream fibre-side topology of FTTx, upstream of the green cab.

If for example there is a link to another more important Ďnew POPí exchange from a minor local one, are we saying that all FTTC cabs would have new long fibre links to the new POP even though it is much much further away? Apologies for being stupid.

Think this has been answered.

As for a dry space, well no they don't need a dry space.  Mostly fibre is jointed and in manholes in the ground which are often wet, damp or full of water.  The joints are made to be waterproof and work fine under those conditions.

Because BT FTTP is GPON this works passively.  There are no switches or other electrical kit required except at each end, essentially a laser fires down at the exchange and it arrives at the customers premise and vice versa along the fibre.

It is true some other fibre companies use a different type of network with fibre and will require active electrical kit along the route, but not so with Openreach.

Regards

Phil
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Weaver

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Re: Future of ADSL EO lines
« Reply #29 on: September 17, 2019, 12:41:03 AM »

@j0hn, PhilipD - It seems that my ignorance of modern post-arrival of FTTC systems is no less enormous than I had anticipated. Many thanks.

The thing about a dry, warm place was an assumption that powered, active kit would possibly be needed, for reasons unknown. I was thinking that aggregation might be required which itself would require mux / demux. But now I think about it, I see that there is no likely need. The individual FTTC cab is perhaps addressed by MAC address (or by the combination of MAC address + VLAN tag?) and then perhaps no need was found to mux the upstream links from multiple FTTC cabs together, because perhaps it costs little more to put two physical fibre links into a duct than one, since arranging the ducts and the labour for blowing the fibre is all that matters in cost terms, and this would be compared to losing the requirement for an otherwise unnecessary active node. Anyway, all wrong thinking on my part, but maybe driven by Highland Think unconsciously perhaps, assuming large distances between nodes with lots of nothingness in between.
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