Potential of FTTdp + G.Fast

Of course, those of us who love our speed would like to have full-fat FTTP, but I completely get why most areas won't be seeing it for a long time.

The idea of FTTdp combined with G.Fast in the meantime interests me greatly as the hype around it suggest it's almost as good as the real thing, but I have been wondering something. I live in an area where the telecoms infrastructure is underground, but would the "distribution point" mean the small single BT manholes dotted all the way along my street, or the larger double-cover one at the very end?

If it's the small one, that is pretty much right outside the door. Even the larger one would give us a boost over the FTTC we have now, though, as it would shorten our copper run to about 200m. My line is currently a relatively long 800m-ish (maybe more) to the cab leading to 30Mb speeds.

I understand that even BT don't fully know the real-world impact of FTTdp and G.Fast yet, but I'm certainly interested in knowing what the "dp" can be, exactly.

G.Fast on a short enough loop, 70m - 100m, will do 1.3Gb/s, shared between upstream and downstream.

G.Fast doesn't have a frequency band for upstream and another for downstream, the division between them is time, not frequency, so the entire bandwidth alternates between upstream and downstream depending on requirements.

1Gb/s down, 300Mb/s up services are possible, as would be 650Mb symmetrical to give 2 examples.

I remember reading something about the time vs. frequency thing - would this have an impact on latency while transferring both ways, or is it simply so fast that it becomes unnoticeable? I would imagine the faster the sync speed, the less of an impact the time division has due to more packet throughput in a certain time.

FTTP using GPON is also time division multiplexing, as there is only one frequency each way (narrowband, LOL).

The DP in underground services is indeed a junction box hiding in a manhole.

In reply to a post by yarwell:

FTTP using GPON is also time division multiplexing, as there is only one frequency each way (narrowband, LOL).

Not quite the same thing. The TDM in GPON is used to share the same carrier with multiple endpoints, in G.Fast there's no frequency set aside at all for upstream, upstream carrier isn't shared between multiple endpoints. Latency on a GPON network can increase as requests for upstream bandwidth rise and each node has to wait longer to be granted its next slot, this can't happen in G.Fast as you're only competing with yourself for slots.

At some point I'll dig my head into how G.Fast works in that regard. I'm familiar with DOCSIS and GPON's request - grant - transmit cycles but am not sure how G.Fast's multiplexing of the resources works. Given vectoring is a required part of the standard there's no reason why each line couldn't run on an independent fixed profile regardless of bandwidth demands, lack of vectoring affects G.Fast profoundly.

In reply to a post by Senn:

Of course, those of us who love our speed would like to have full-fat FTTP, but I completely get why most areas won't be seeing it for a long time.

Alongside the excellent technical discussion so far in this thread, you have to consider the economic and legal issues around FTTDP v FTTP.

To a rough approximation, FTTDP and FTTP involve running the fibre network approximately as deep, so to that point the costs are the same. (There will, of course, be some variance depending on the size of the DP compared to the typical 8 or 12 way split of an FTTP beam splitter).

The question is what option is cheaper from that point.


FTTP involves running a fibre into the premises, but does not involve installing expensive active equipment at the DP, there's no need to get power to the DP, and the installation part of FTTP is pretty much a 'once and for all' deal so far as future network upgrades go. Openreach have already run co-existence tests with prototype 10GPON over their FTTP infrastructure in Cornwall - all they had to do was fit 10GPON equipment at the subscriber and head-end, whilst GPON users on the same split remained unaffected.

FTTDP uses the existing metallic pair from the DP, but does involve installing expensive active equipment at the DP which needs power (which might be back-fed from the end-users). There is fibre at the DP which could be converted into 'full' FTTP later, but if there were future upgrades to the FTTDP technology, you'd have to change the equipment at the DP.


It may well be that both options are rolled out as fibre moves ever deeper into the network.

FTTDP is particularly attractive for multiple-occupier buildings such as flats, because the cables from the DP are typically short, and there's no need to get freeholder permission to run a fibre through the building to each served property.

For houses, it might turn out to be more cost-effective (especially over the medium to long term) to skip FTTDP and go straight to FTTP.


Obviously the economics of both FTTDP and FTTP will change over time as installation techniques are refined and the equipment gets cheaper.

At the moment, it's a hypothetical comparison as commercial FTTDP equipment is some way off and the focus for the next 5 years or so is on the BDUK project targets. It is possible that FTTDP will prove useful in the later stages of the BDUK project. I'm less sure we will see near-term widespread use of FTTDP as a speed enhancement product for those whose connections already qualify as superfast.

the thing that bugs me is such a service will still be subject to the openreach pair lottery, different areas with different quality pairs, so 100m performance is not the same in one area as another.

In reply to a post by David_W:

To a rough approximation, FTTDP and FTTP involve running the fibre network approximately as deep, so to that point the costs are the same.

This is why I'm thinking it's more likely they would end up (at least for streets like mine) making the DP the larger manhole at the end of the street, rather than the small ones outside pretty much every other house. Bringing the fibre almost to everyone's door could, as you say, mean that FTTP actually becomes the better option economically - especially when future-proofing is considered.

So many uncertainties at this point. 30Mb FTTC is doing me well today, but unless I move elsewhere, I figure I'm not going to see anything better for years...

IF you're not in a densley populated area, I would expect LTE to provide better performance than fixed line solutions in that timeframe.

Considering 3G is absolutely terrible here, I don't expect the mobile-focused access technologies to overtake fixed-line solutions for my interest in a fair while.

In reply to a post by Senn:

This is why I'm thinking it's more likely they would end up (at least for streets like mine) making the DP the larger manhole at the end of the street, rather than the small ones outside pretty much every other house.

There are almost certainly DPs already in situ, where the D side multi pair cable from the PCP cabinet terminates in a joint and is connected to the cables running to the end users. It is, of course, an open question whether Openreach would reconfigure the network if they installed FTTDP.

A small manhole outside each property is more typical of a cable provider than Openreach, but if the site is sufficiently new, it's possible that the same policy as the cable networks has been followed, with a small chamber in the duct work near each property. There won't be a DP in each small chamber.

Edited by deleted (Mon 18-Nov-13 17:09:32)

In reply to a post by David_W:

A small manhole outside each property is more typical of a cable provider than Openreach, but if the site is sufficiently new, it's possible that the same policy as the cable networks has been followed, with a small chamber in the duct work near each property. There won't be a DP in each small chamber.

I can confirm these are BT (and hence Openreach) manholes as it has "BT" on the covers, and that there are roughly 2-3 houses per hole. I haven't personally seen what is inside them, but I do know that things had to be done to a few of them due to last year's activation of FTTC. What that work was I am unsure, but a nearby friend asked the Openreach engineers what they were up to outside her house, and the answer had "something to do with superfast fibre". This was before the cab was activated so it wasn't simply customer activation. You'll have to forgive me, there are many things about the actual physical infrastructure I'm most likely clueless on.

For reference, this estate was built in 1983, and all the infrastructure is underground. I would estimate there are just over 100 houses along this street, and there is at least one large BT manhole at one end (which would be, I'm assuming, the intended DP if this technology ever goes commercial). There are also no cable services in my town at all.

Whether g.fast will appear I believe will depend on how sales of FTTPoD pan out....

Low sales will be a gift to the camp that says FTTP is too expensive and decades long payback

In reply to a post by MrSaffron:

Whether g.fast will appear I believe will depend on how sales of FTTPoD pan out....

Low sales will be a gift to the camp that says FTTP is too expensive and decades long payback

yes the old clash of short termism vs long term good for country.

To me it its simple, if the biggest telecom company in the country deems it not enough profit then the gov should takeover and roll it out.

However I dont want BDUK style rollout where the government funds and the private company profits, any such rollout would stay in government ownership until a private company pays the going rate for the assets. Ask how to pay for it? cancel HS2. HS2 going through my countty but no stops, only realistically speeds up travel to leeds and by a small amount, huge waste of cash in comparison to a national rollout of FTTP to promote homeworking.

In reply to a post by Chrysalis:

yes the old clash of short termism vs long term good for country.
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Ask how to pay for it? cancel HS2.

In reply to a post by Chrysalis:

Ask how to pay for it? cancel HS2. HS2 going through my countty but no stops, only realistically speeds up travel to leeds and by a small amount, huge waste of cash in comparison to a national rollout of FTTP to promote homeworking.

HS2 might be good for the country, but to terminate at a central london station is equally short sighted, when over half the people who might want to get north by train don't live in london - and would have to use the overcrowded existing services to get their first. (So bypassing all trains and driving is still more preferable).

Yes, HS2 should be done after broadband is sorted.

to me HS2 is been behind the curve.

other countries had these sort of trains a decadeor so ago, now its not about travelling to places faster but avoiding the need to travel at all.

Of course I agree on the bad placement of stations as well, the catchment areas that HS2 supposedbly benefits is just the usual, london etc. Apparently putting a stop between derby and nottingham is good for leicester as well, I wish we could somehow forbid the line going through leicestershire in protest. But yeah I guess only london matters.

I've been hoping for a sliver of common sense for ages now in that the HS2 cash be spent on the broadband infrastructure all over the country.

Alas, politicians.

In reply to a post by Chrysalis:

the catchment areas that HS2 supposedbly benefits is just the usual, london etc.

The politicios don't get it do they. I'm only 35m from central london, and 20 from Heathrow, and I'd bite my arm off instead of getting a train into London and out again for a long trip. On a trip to the north east last year I drove. Obvious when you have to take any more than a small backpack with you. C'est la vie.

Edited by jchamier (Mon 18-Nov-13 21:38:09)

In reply to a post by MrSaffron:

Whether g.fast will appear I believe will depend on how sales of FTTPoD pan out....

Low sales will be a gift to the camp that says FTTP is too expensive and decades long payback

As far as I can tell, and speaking with a couple of people in the know seems to bear this out, the only thing that'll stop deployment of it will be if the trials go very wrong. Cost savings of not having to do that final drop are still non-trivial even with the costs of the DP kit.

In reply to a post by Ignitionnet:

As far as I can tell, and speaking with a couple of people in the know seems to bear this out, the only thing that'll stop deployment of it will be if the trials go very wrong. Cost savings of not having to do that final drop are still non-trivial even with the costs of the DP kit.

How invasive/expensive-to-install is FTTP at the user end? I imagine it would vary depending on property, and the FTTdp solution would also mean the in-house wiring can remain as-is. To "fibre up" my house, the cable would have to replace the existing copper coming in under the front door, into a cupboard outside the kitchen and through the wall to the current master socket. Easy compared to some, perhaps.

In reply to a post by Senn:

How invasive/expensive-to-install is FTTP at the user end?

A termination box inside or outside the property can deliver a Cat5 type ethernet connection to a switch with wireless capability.

Fibre needs larger radius bends than copper.

In reply to a post by jchamier:

(So bypassing all trains and driving is still more preferable).

Definitely preferable. My journey to work by car takes about 55 mins door to door, going by train takes around 90 mins.

In reply to a post by Ignitionnet:

As far as I can tell, and speaking with a couple of people in the know seems to bear this out, the only thing that'll stop deployment of it will be if the trials go very wrong. Cost savings of not having to do that final drop are still non-trivial even with the costs of the DP kit.

I've seen bar-charts that depict the relative costs for FTTC, FTTdp, FTTP and another option FTTW, though not specific to a UK rollout. Unfortunately, I can't find them at the mo.

Both FTTC and FTTdp are cheaper than FTTP in total rollout cost - simply because, for every DP box there will be 10-30 subscribers who don't get that final 100m of fibre. Each of which doesn't need an appointment for the final install, which seems to be the real problem.

To put the cost of those appointments into context, look at FTTW:

FTTW, where W=Wall, is a scenario where fibre goes to an external wall of every property. At the wall, an electronic box would be installed to convert back to copper for the final run inside the property - a domestic version of FTTB. The electronics would be an OLT and something like a single-channel modem for G.fast, so very similar to a small FTTdp box.

The advantage of FTTW would be that no appointments would need to be made with the householder, while the downside is obviously the addition of the extra box of tricks - more cost, more power problems, and more maintenance.

Those bar graphs showed that, in total, FTTW cost the same as FTTP!

That means the cost of each appointment is roughly the same as the long term cost of a small FTTdp box (CapEx + OpEx).

I'm pretty sure that FTTdp is going to be cheaper, and is highly likely to be perceived as a worthwhile step for a big chunk of the country.

So, as you say, the only thing likely to stop it is if it just doesn't work from a technical perspective.

FTTW sounds kinds like how timerwarner do there cable.

Openreach FTTP is two visits

1. No need to get into property, but wayleave/permission needed to attach box to outside wall and the final 20 to 60m of fibre is blown in ducting or new overhead tube to a termination unit.
2. Second visit a pre terminated fibre is connected and run inside the property to the ONT and battery backup if a telephone also using the fibre.

Old estimates was 7 hours to do both, now try employing a plumber for 7 hours and think of the cost.

I suspect that where a FTTPoD connection was already live, then no g.fast but the GEA pricing would let others order for same price in a good few years.

I hadn't heard of FTTW before, but it would likely not work without appointments for a lot of houses. Quite a few of them in my street alone have front doors that step out onto the pavement, so connecting any equipment up would have to be done on the homeowner's property or land.

I guess it makes me think of my original question - it seems to be the consensus that my nearest DP would be the large manhole at the end of my street, but to bring the infrastructure closer to the "FTTW" concept, the fibre would have to be blown to the small manholes outside every other house.

Secretly hoping (false hope, I know) for this in the not-so-near future.

Before I finish my house extension I'm going to make sure I have a tube that runs from an external wall into my server room, just in case real fibre comes my way.

It will be far cheaper. Full FTTP would tax several hours of work at each premises

Given how close to the Home FTTD gets there is little advantage of full FTTP for residential premises

Getting the cost of FTTD down and demand are going to be the two key issues

Never heard of FTTW, it's the same as FTTP as far as I'm aware. Some Verizon FiOS installs use an external ONT. Still requires a home visit as there's still the requirement to get power to the ONT, and to connect the internal home network / CPE to the ONT.

You have a server room?

In reply to a post by Ignitionnet:

Never heard of FTTW

Virgin Media is FTTN

In reply to a post by Ignitionnet:

You have a server room?

He's not the only one. I've got a partitioned off section of the garage with its own power feed and air conditioning. There's a 27U rack in there, with two gigabit fibre links to the house.

In reply to a post by Ignitionnet:

You have a server room?

It's not as good as David_W setup, and it doubles up as a cloakroom (coats and shoes) as well, but I like to call it the server room, it does have a server in it after all Also a gigabit switch and gigabit newtworking to virtually every room in the house.

Here's a picture from from my xDSL extension guide.. The room is decorated now, and pretty full of coats and shoes too, and nice and warm in the morning when I put my boots on

Edited by R0NSKI (Thu 21-Nov-13 19:02:51)

Thank you for that. FTTC is actually FTTN too, just referred to in the UK as FTTN.

And neither have anything to do with FTTW

I cannot say I have ever felt the inclination to do something that elaborate, nor do I have any use for such a thing.

Perhaps it's a side effect of working with the stuff on a daily basis; I keep it very simple at home with just an off the shelf NAS enclosure from Amazon supplying storage, a switch, and a wireless bridge.

If I need to mess with things I have a 32GB RAM dual-Xeon server running ESXi so can replicate most things 100% virtually.

In reply to a post by Ignitionnet:

Perhaps it's a side effect of working with the stuff on a daily basis; I keep it very simple at home with just an off the shelf NAS enclosure from Amazon supplying storage, a switch, and a wireless bridge.

Ditto - I have a NAS, a desktop PC, and a laptop.

All the rest of that technology is what I do at work for a living, so I like to not have a server room at home

In reply to a post by Ignitionnet:

I cannot say I have ever felt the inclination to do something that elaborate, nor do I have any use for such a thing.

That setup was installed because we have people working from home with a need to host things locally. It got the noisy, heat generating servers out of the house and allowed the use of rack mount gear to save space. The fans of rack mount servers can, as many here are aware, be extremely noisy at times.

nice setup