Is ISP congestion/contention still a thing?

Years ago before FTTC really took off and ADSL dominated, ISP contention and congestion on their network was a real problem for some.

Going for the cheapest option, often meant the ISP didnt have the capacity and was oversubscribed, resulting in slowdown or dropped packets at peak times.

Having not changed ISP for years is this still a consideration when moving, or has the issues largely gone away?

Edited by bobble_bob (Fri 25-Feb-22 08:45:33)

In reply to a post by bobble_bob:

Years ago before FTTC really took off and ADSL dominated, ISP contention and congestion on their network was a real problem for some.

Going for the cheapest option, often meant the ISP didnt have the capacity and was oversubscribed, resulting in slowdown or dropped packets at peak times.

Having not changed ISP for years is this still a consideration when moving, or has the issues largely gone away?

Not directly related to Contention Ratios, but an area that became quite talked about following the first lockdown was Cross-Talk in the cabinets for FTTC services. Because so many, many, more people were suddenly working from home and the level of data now suddenly needing to be services by the cabinet systems – they were overwhelmed with cross talk issues, resulting in regular broadband drop outs, almost every day.

I had Sky ADSL for many, many years, which was as solid and a rock until lockdown. Once under lockdown my ADSL started suffering frequent dropouts – some lasting for hours and even days! Sky and Openreach could not find anything wrong. In desperation I then upgraded to FTTC, which did improve things, but I would still get daily dropouts, but at least they were only lasting for under a minute each time they happened – but still very annoying. Eventually I was able to upgrade to FTTP, which has been rock solid.

When you read on other forums, there does seem to be a disproportionally large number of people suffering dropouts, that did not, before lockdown – obviously some of these are typical actual line faults.

With a lot of people now taking up permanent home working, I wonder if the Openreach cabinet infrastructure QoS was never really designed for a close to 100% saturation – hence the cross-talk issue that is now with FTTC customers for good.

Someone here may have a more accurate summation.

Could some of that crosstalk simply be people upgrading to FTTC in lockdown?

I know a few at our place that once lockdown hit and working from home became a thing, they upgraded to FTTC. Reason being they suddenly had kids wanting to stream Netflix while the parents needed to work , so needed that extra speed

Think its always been said the more on FTTC in a cabinet the more likely crosstalk is. Covid just made the process happen almost overnight

Edited by bobble_bob (Fri 25-Feb-22 10:30:13)

Crosstalk isn't something new since WFH. It's just some cabinets that suffered little from it now suffer a lot from it.

My cabinet has suffered really bad crosstalk since it reached around 250 subscribers back in 2015. It now has 2 DSLAMs and had over 550 subscribers until Virgin covered the entire area in late 2020 so has probably improved since WFH started.

Crosstalk is the interference emitted from multiple twisted pairs tight together in a bundle and nothing to do with cabinet saturation. It gradually lowers sync speed over time (both upstream and downstream).
Vectoring can be deployed to mitigate the effects of crosstalk but Openreach haven't deployed Vectoring on any of their commercially funded cabinets.
A single bad crosstalker can knock as much as 20Mb off a lines sync/attainable rate.

I wonder if the Openreach cabinet infrastructure QoS was never really designed for a close to 100% saturation

The DSLAMs are actually designed to deal with much more traffic than Openreach pushes through them.
In some networks these DSLAMs are installed much closer to residents so can deal with much higher sync rates/throughput than Openreach sell.
Openreach restrict sync on the DSLAMs to 80/20 at the maximum where as in other countries they will have customers syncing at 140/40.

Most congestion suffered on FTTC is on the cablelinks (in the exchange) or on the backhaul (beyond the exchange).
There is the odd FTTC cabinet that has capacity issues between it and the OLT but that's down to Openreach not upgrading it in time and not a limitation of the DSLAMs themselves.

In reply to a post by j0hn83:

Most congestion suffered on FTTC is on the cablelinks (in the exchange) or on the backhaul (beyond the exchange).

This does remain an issue, I experienced it with a Sky FTTP circuit earlier this year. It's hard to predict, though - with the access lines being the same you're into the murky world of 'who runs a better network' and stays on top of link capacity management.

My personal feeling is that this is often unrelated to the price paid for the service: there are likely to be a few readers here who would give Zen a wide berth despite their historic reputation as one of the better options. Anecdotally I have heard of BTw cablelinks beoming congested but a half-decent ISP should be able to get BTw to resolve this. I haven't heard of the issue arising with TalkTalk business (wholesale) backhaul, but this may just be due to lower market share.

These issues are all likely to be highly localised and backhaul utilisation data isn't generally something that gets shared outside an ISP.

Not directly related to Contention Ratios, but an area that became quite talked about following the first lockdown was Cross-Talk in the cabinets for FTTC services. Because so many, many, more people were suddenly working from home and the level of data now suddenly needing to be services by the cabinet systems – they were overwhelmed with cross talk issues, resulting in regular broadband drop outs, almost every day.

This isn’t correct, crosstalk is an issue due to the proximity of other digital circuits with a specific cable.
Whilst I agree there are more people more reliant and therefore more critical of their circuits stability due to home working, this hasn’t increased crosstalk especially. The circuits are left in sync 24/7, (unless the owner is foolish) , so your theory doesn’t hold water.

Thanks for correcting my technical faux pas.

I would be very interested to know your hypothesis for why mine and many other people’s broadband connections suddenly started frequently dropping out once lockdown was enforced?

Before lockdown I know of many people, including myself, that used to have very reliable connections with dropouts being a very rare thing. To go from almost no dropouts – maybe once every 6 months, to having 3-4 almost every day – something is not quite adding up…

Unless, Openreach systematically carried out some type of orchestrated change of equipment all at the same time, causing the new frequent dropouts. The cross-talk was the only plausible explanation that corresponds to covid lockdown – unless the Openreach systems also caught covid !

In reply to a post by Zarjaz:

Whilst I agree there are more people more reliant and therefore more critical of their circuits stability due to home working, this hasn’t increased crosstalk especially.

Anecdotally, I became aware of more areas where FTTC was at capacity/waiting list status in the second quarter of 2020, perhaps due to additional lines being ordered for homeworking. If this can be backed up with data, the increased number of active VDSL signals per D-side cable could offer an explanation.

It only needs one new FTTC connection to create cross-talk with an existing one, if they happen to be next to each other in the link cable between the PCP and Fibre cabinets, or in the copper from there to the premises.

Accepting your suggestion that a lot more upgrades from ADSL2+ to FTTC happened during lockdown, it isn't surprising that the number of dropout reports has increased. Though I am surprised at actual dropouts rather than just noticeable speed drops.

Unless the upgrades were from slowish ADSL2+ and they didn't gain much anyway. VDLS2 which is what comes down the line from the fibre cabinet via the PCP. VDSL2 attenuates much more the ADSL2+, and also the frequencies in use are very different.

Edit: Typo "VDSL2+" corrected.

Edited by pluralist (Fri 25-Feb-22 19:29:49)

Though I am surprised at actual dropouts rather than just noticeable speed drops.

Exactly that Bob.