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[bogof]

How does this actually work with the speed guarantees?  Are they just betting on the spread of customer takeup and usage patterns meaning that the guarantees offered will hold for 99.9% of areas?  Or does the guarantee only cover the optical interface layer, and not actual achievable throughput?

Is the 2.5G down shared between 32 or 128?  I thought it was the former, but it sounds like you're saying there could be up to 4x32 port splitters on a single 2.5G network?

So far as I can see I'm still the only one on my local network, though I'm sure it won't stay that way for long.  Looks like Openreach have overbuilt the GFast area one street down from me with FTTP now, all the CBTs have started appearing on walls.  In the last few weeks it looks like hundreds of extra CBT ports have started appearing. 

[RealAleMadrid]

There seems to be some confusion with the terminology here. A splitter node will have 4 fibres back to the exchange and can contain up to 4 Splitter assemblies, each SASA has one fibre splitting to 32 premises so it is 2.5Gbps downstream shared between 32 premises. Am I right?

[tickmike]

I had sent a picture of the van and guy who was messing with the manholes to work as we had been having problems with the internet and as I was working from home I couldn't do any work and just to prove I wasn't skyving I took a picture to send to work. This was taken on the 21st March. Does anyone think this could be related to FTTP happening in our street?

Looks like a  splitter node in the photo (not to clear a photo) ?.

Put your details in
https://www.broadbandchecker.btwholesale.com/#/ADSL

[Black Sheep]

There seems to be some confusion with the terminology here. A splitter node will have 4 fibres back to the exchange and can contain up to 4 Splitter assemblies, each SASA has one fibre splitting to 32 premises so it is 2.5Gbps downstream shared between 32 premises. Am I right?

That is correct.

Ultrafast BB is anywhere between 300-1000Mbps, and on the OR architecture you could receive a constant 330Mbps DS and 30Mbps US, if that's the package you chose ??

GPON is the technology being used to deliver this, but if and when higher speeds are required, there are other tech's available that can deliver the updates over the same network that is being installed right now.

[Black Sheep]

Looks like a  splitter node in the photo (not to clear a photo) ?.

Put your details in
https://www.broadbandchecker.btwholesale.com/#/ADSL

Hi Mike

Pipster is all over it - see earlier quote - "Honestly fantastic news. Not taking orders yet but I’ll be forced on there daily from the kids. Can’t thank you enough" 

[Alex Atkin UK]

That is correct.

Ultrafast BB is anywhere between 300-1000Mbps, and on the OR architecture you could receive a constant 330Mbps DS and 30Mbps US, if that's the package you chose ??

GPON is the technology being used to deliver this, but if and when higher speeds are required, there are other tech's available that can deliver the updates over the same network that is being installed right now.

I'm very confused, you literally just said it splits one fibre into 4 each serving up to 32 customers each, so that would be 2.5Gbit shared over 128 customers.

My assumption is that once customers reach a certain number then new customers would be will be provisioned on XGPON which runs on different frequencies so can run concurrently with GPON, until such time its preferable to upgrades existing customers ONTs?

[niemand]

Ah I see, I didn't realise the 32 was from the splitter and that several PONs come from one fibre back to the OLT.  So effectively the network has potentially a 128:1 contention ratio?  Though presumably its unlikely for every premises passed to be live and many will take slower profiled services.

That does make a lot more sense from a cost perspective.

No, using Openreach speak each fully loaded PON of 4 SASAs has a fibre for each SASA plus spares. One SASA = one fibre = 30 premises passed with 2 spare ports.

2.4 Gb/s / 30 = 80 Mb/s worst case downstream, 40 Mb/s worst case upstream.

Contention ratio kinda irrelevant but with gigabit services even if everyone purchased one 30 / 2.4 = 12.5:1 or 25:2.

There are 32 premises sharing a fibre with me. The most the other 31 folks in total use, even in bursts, is 700 Mbit/s or so and that level of usage is very transient. As long as the link never fills whether contention ratio is 1:1 or 1000:1 doesn't matter.

People need to know what they’re really buying and should not be sold 900 Mbps headline rates if contention could bring it way down to who knows what.

As long as capacity planning ensures that 'who knows what' never happens it's not an issue.

Contention on the CableLink and exchange backhaul will be far higher than that on the PON.

My assumption is that once customers reach a certain number then new customers would be will be provisioned on XGPON which runs on different frequencies so can run concurrently with GPON, until such time its preferable to upgrades existing customers ONTs?

As of right now if the customers served by a SASA have capacity issues that 30/32 properties will be split across 2 x 16 port SASAs. There's no production XGSPON ONT available on the Openreach network and the service hasn't been specified for production only trials.

How does this actually work with the speed guarantees?  Are they just betting on the spread of customer takeup and usage patterns meaning that the guarantees offered will hold for 99.9% of areas?

Yup. Capacity planners are in a job for a reason.

[Black Sheep]

I'm very confused, you literally just said it splits one fibre into 4 each serving up to 32 customers each, so that would be 2.5Gbit shared over 128 customers.

You're correct .... you are very confused. I never said it splits one fibre into 4 each serving 32 customers each.

[bogof]

No, using Openreach speak each fully loaded PON of 4 SASAs has a fibre for each SASA plus spares. One SASA = one fibre = 30 premises passed with 2 spare ports.

2.4 Gb/s / 30 = 80 Mb/s worst case downstream, 40 Mb/s worst case upstream.

Contention ratio kinda irrelevant but with gigabit services even if everyone purchased one 30 / 2.4 = 12.5:1 or 25:2.

There are 32 premises sharing a fibre with me. The most the other 31 folks in total use, even in bursts, is 700 Mbit/s or so and that level of usage is very transient.

What happened to the 2 spares?  Isn't that 29 other folks with 2 spares?
Out of interest, how do you know the rest of the usage amounts to 700Mbit?  And what does that translate into for you - does the timeslot architecture mean that at that level of utilization you could still saturate gigabit, or does that level of utilization mean that when that's happening the timeslots you get prevent you from achieving gigabit? (it doesn't seem like a given to me that 700mbit being used means you definitely get access to the rest )

As of right now if the customers served by a SASA have capacity issues that 30/32 properties will be split across 2 x 16 port SASAs. There's no production XGSPON ONT available on the Openreach network and the service hasn't been specified for production only trials.

How would the physical implementation of that look?  I mean, the fibres our CBT is on got spliced up to the splitter (I guess, they were huddled in the back of a van over a large chamber for a day).  Would they have to come back and re-splice all those ports again?  Or is any of the SASA stuff connectorised?  Sounds like it would be pretty invasive.

This is all just academic interest in the interest of science.  I know many of my neighbours and I can't see any of them even being bothered to take it, let alone giving it a good workout.  I, on the other hand, am much enjoying the speed boost!!

[j0hn]

He knows the usage of the PON because he purchases enough to fully saturate it.

2 x 1Gb and a 3rd line at 330Mb/s I believe (Carl can correct that).

My assumption is that once customers reach a certain number then new customers would be will be provisioned on XGPON which runs on different frequencies so can run concurrently with GPON, until such time its preferable to upgrades existing customers ONTs?

XGS-PON has only been trialled. The trial was only for business customers and I believe was only available on specific sites.
It closed to new orders back in January.

https://www.openreach.co.uk/cpportal/updates/briefings/ultrafast/nga203020

The flexibility to use it on PONs in the future exists but current usage is way below what each PON is capable of and will be a few years till it will be an issue.

OpenReach's committed rates are not very high on the downstream for their higher tier products.

People need to know what they’re really buying and should not be sold 900 Mbps headline rates if contention could bring it way down to who knows what. It is what it is though and it’s a way of giving a cost effective service for the most part to many people, and if you want a better guarantee then I suppose you can always get a dedicated line? For silly money?

If you want 1:1 contention (or even 2:1 or 5:1) you're going to pay a pretty penny.

I'm not sure why there's such a fuss about PON contention.
32:1 is pretty good for GPON.
There are plenty of countries where 128:1 is much more common.

If you take the backhaul capacity of an FTTC cabinet and divide by the number of users on that cabinet you will quickly see there's much more contention on a cabinet than a PON.
For example my PCP has a 256 port ECI and a 384 port Huawei cabinet.
The next PCP down the road has 2 x 256 ECI cabinets and a 288 Huawei.

If everyone on either PCP saturated their connection at the same time their throughput would be considerably below what it would be if everyone on a PON used their connection at the same time.
That's not how people use their broadband connections though.

Carls usage is not the norm.

[Alex Atkin UK]

A splitter-node (affectionately called a PON) is planned to have a maximum of 4 SASA's. Each SASA is capable of feeding 32 connections = 128 maximum.

But, we plan to 120THP (connections) .... this can be upped with high-level authority but certainly isn't the norm.

If you have 2.4Gbit down and 1.2Gbit up, and all traffic goes to all customers, how is it not shared between all 128 premises? (or 120 in the case of Openreach)

Is the data transfer rate actually four times higher on the fibre but its the time slots that allocate only 1/4 max to each ONT?  Thus why its considered 2.4Gbit down and 1.2Gbit up max?  I've not seen this explained anywhere.

XGS-PON has only been trialled. The trial was only for business customers and I believe was only available on specific sites.
It closed to new orders back in January.

I was thinking more on what they would do moving forwards, but obviously as my understanding of how a PON works seems to be flawed to begin with, this is not necessary to solve the problem?

The flexibility to use it on PONs in the future exists but current usage is way below what each PON is capable of and will be a few years till it will be an issue.

OpenReach's committed rates are not very high on the downstream for their higher tier products.

If you want 1:1 contention (or even 2:1 or 5:1) you're going to pay a pretty penny.

I'm not sure why there's such a fuss about PON contention.
32:1 is pretty good for GPON.
There are plenty of countries where 128:1 is much more common.

Its not that were making a fuss, just trying to get our heads around how it works.

Like you said, 32:1 is good, 128:1 however.....

I mean while it might sound bad that you [could] get contended during peak hours, especially when a new game releases.  I think its fair to say that most of the contention at such a time will still be at the CDN anyway, so having the fastest link in the world isn't going to make a blind bit of difference.  Too many people buying Gigabit don't seem to understand that, never mind when they're trying to do it all over WiFi.

[j0hn]

If you have 2.4Gbit down and 1.2Gbit up, and all traffic goes to all customers, how is it not shared between all 128 premises? (or 120 in the case of Openreach)

The confusion above seems to simply be OpenReach terminology.

OpenReach deploy GPON with a 32:1 split.
A single OLT port in the exchange feeds a single fibre to the Splitter, which is then split up to 32 ways.
The exact same data is on each of the 32 fibres but they are encrypted so only your ONT can see your data.

To me, that's a PON.

OpenReach simply put 4 separate splitters in a single chassis/housing.
Each splitter has its own fibre, with its own OLT port.
The data from each splitter is separate. The bandwidth for each splitter is separate.
OpenReach aim to keep 2 ports free per splitter, so really 30:1.
All 4 splitters in the single housing are labelled as "PON 1" for example, so 120 properties per "OpenReach PON" but there's actually 4 separate PON's there, each with their own fibre and OLT port.

[Weaver]

Thanks J0hn, that deconfused me. 

[bogof]

He knows the usage of the PON because he purchases enough to fully saturate it.

2 x 1Gb and a 3rd line at 330Mb/s I believe (Carl can correct that).

OK, interested to know how that's measured then.  If it's measured by achieving 1.8G (leaving 0.7G unaccounted for) then it would seem that the demand from the other customers was likely higher than 0.7G; they just got given max 0.7G as their fair share during the saturation time?  If Carl's demand goes away it sounds like the others would use more of the bandwidth.

I thought perhaps Carl had some insight into the port statistics from the exchange or similar which would be exciting

---

How does CBT port allocation and ONT selection work?
I live in a terrace of 8 houses, they've put in an 8 port CBT in a chamber that they could all reach without much drama.  I'm the only one on the CBT at the moment.
Are any of the ports locked and allocated to other properties even though they've not taken a service?  Or is it truly first-come-first-served?

The wholesale checker says:
"Our records show the following FTTP network service information for these premises:-Single Dwelling Unit Residential UG Pre built to curtilage Hard.

ONT exists with active service. No spare ports are available. A new ONT may be ordered."
This seems to match up with my ONT being single port, so the ONT is "full"

If I ordered another additional service or 2 (I'm coming for ya, Carl! :-p lol) then would OR pull more fibre from the CBT into the house and put in another single port ONT, or come out and replace the ONT with a unit with more ports?  I guess from an IT robustness point of view the former is probably preferable (though the street fibre is the same, it gives some robustness to CBT port going bad, fibre damage to internal fibre, splice failure in the CSP, and failure of the ONT itself).

[niemand]

Buy One Get One Free:

Spares - Openreach messed up the build for this new build estate. 96 properties. They put it across 3 PONs. PONs as it what a PON actually is, the Passive Optical Network connecting to a single port at the OLT in the headend exchange, not Openreach speak 

There's some fairness about how bandwidth is split, it's not a free for all. Other customers wanting bandwidth would get preference over me. I drop to about 1.6 Gb/s and the 700 Mbit/s was an overestimate. I'm not sure exactly how much bandwidth GPON can provide but a reminder that the 2.488 Gbit/s downstream comes with overheads that'll be stripped away by the ONTs.

A split could be done in a few different ways but would be disruptive either way. The outage would be minimal.

If you ordered another service you'd get a second ONT. 4 ports aren't generally available from Openreach for right now and the existing ones can only handle a gigabit in total.

John: I very, very, very rarely saturate all the services with anything other than occasional speedtests done to either annoy people or to check that everything is working as it should be.

The three are there mostly due to specific WFH needs and will be brought down to two in 2022.