One broken fibre - town outage?

Recently, during the Covid19 isolation period the town has experienced a couple of cable breaks that have caused carnage.

First was a major break that wiped out TTb, Virgin Media and Sky LLU services.

Second one today, has wiped out Sky across the town.

How can one cable break wipe a towns LLU connection out yet BTw remains up and connected?

I read somewhere once that FTTC cabs can be fed from a different exchange, like a main headend exchange. In this town, every exchange has TTb and Sky LLU so would that still be the case? They're reasonably big exchanges.

Without sounding like I want sensitive network topology information, which I don't, is there a main spine fibre that runs through a town for the LLU networks? Is there more than one main fiber feeding a town for BTw based connections at exchanges?

You just don't hear of a group of exchanges being wiped out on BTw based connections.

Edited by wolvesmad (Sun 28-Jun-20 21:48:03)

Lotta LLU is daisy chained rented circuits with little or no resilience.

I have seen a fence post snafu take out 35 thousand Sky customers.

Because BTw network are much better than LLU network. I am glad that Plusnet remain BTw (Dedicated WBMC) rather than LLU - Easynet/sky network

In reply to a post by wolvesmad:

You just don't hear of a group of exchanges being wiped out on BTw based connections.

Just to clarify, these will be different fibres to those that connect to the cabinets in the street. The Openreach cabinet fibres connect back to a handover exchange (which may or may not be your local one).

At the handover exchange there are a handful of network providers, BTwholesale, TalkTalkBusiness, Sky and some smaller operators. These providers then have to connect the exchange to their core network.

As described some have multiple connections going in different routes, and others have only one link.

Some of these companies have been around 50+ years, others are 10 to 15 years old. You can pay more (much more!) for resilience. It is a business gamble against how long it takes to repair a major link.

Similar to the police closing the M4, there aren't many other ways to get from London to South Wales.

In reply to a post by partial:

Lotta LLU is daisy chained rented circuits with little or no resilience.

We have a winner. BT Wholesale all the GEA handover exchanges and indeed pretty much every exchange of any size are connected to at least two other exchanges with routes back to the BT Wholesale core. Been that way for historical reasons for a while and has continued on.

Difficult outside of cities to make the business case to deliver such resiliency on the part of the LLU operators.

You were actually quite kind when you mentioned a broken fibre causing a town outage. On service status pages you can often see 15+ exchanges down. This can be a single fibre break at the end of a long daisy chain. An exchange at one end is on its own, connecting to a single other exchange which in turn goes via another exchange, etc, until it reaches the LLU operator's core. The break happens in between that last exchange and the core and you lose every exchange in the chain which can be anything from one to a couple of dozen.

Likewise a break mid-way through the chain severs everything on the one side of it. In the case of BT Wholesale that's not an issue as a single exchange has at least 2 paths back to the core.

Edited by CarlTSpeak (Mon 29-Jun-20 09:05:01)

Also many alternative providers route their cables at the side of railway lines which may not be buried.

These are very vulnerable to attack from cable thieves. This can happen repeatedly as the various gangs move about.

In reply to a post by partial:

Also many alternative providers route their cables at the side of railway lines which may not be buried.

Not so much this. National network which is resilient they might be renting fibre there but the inter-exchange transport network stuff this is unlikely as paths are usually present between them.

They may not be buried indeed but using the troughing by the side of the lines.

My local town exchange has over the years had Vodafone, Sprint and GX networks all dig their way from the exchange back to the railway line so I think there is a fair bit going on obviously dependent on where the railway is and where it's heading to.

My question is who is stealing fibre cable?
I thought that it was copper cable that normally gets stolen

In reply to a post by partial:

My local town exchange has over the years had Vodafone, Sprint and GX networks all dig their way from the exchange back to the railway line so I think there is a fair bit going on obviously dependent on where the railway is and where it's heading to.

National network. There are actually relatively few nationwide networks. The fibre at those points should be a ring so have options you'd hope.