How long is a local loop?

MyName13 · May 21, 2018

As far as I know local loop is a direct link between client and ISP (2 cables).Does this loop run from every client to some multiplexer in a neighbourhood or does it go directly to some ISP building?If it goes to some central spot in the city, isn't having a pair of cables for each customer incredibly expensive?Where would all these cables fit (thousands of pairs few kilometers long)?How would such network even be expanded (every new client would require another pair of cables across the entire city).

Lurick · May 21, 2018

It goes to a multiplexer nearby and then a few cables run to the ISP building or in some cases to another multiplexer and that goes to the ISP. Usually they oversubscribe customers, depending on the area, by anywhere from 10:1 to 100:1 or maybe more.

MyName13 · May 22, 2018

16 hours ago, Lurick said:

It goes to a multiplexer nearby and then a few cables run to the ISP building or in some cases to another multiplexer and that goes to the ISP. Usually they oversubscribe customers, depending on the area, by anywhere from 10:1 to 100:1 or maybe more.

That makes more sense.What do you mean by "oversubscribing"?

Lurick · May 22, 2018

4 hours ago, MyName13 said:

That makes more sense.What do you mean by "oversubscribing"?

So when they have a neighborhood of 100 houses, for example, they'll run a 40Gb line (or several 10Gbit lines) to the local node but sell 1Gbit service to those 100 homes. If all 100 tried to download at 1Gbit/sec at the same time they would hit a bottleneck on the line since there is only 40Gbit of capacity out of the local node back to the ISP. If my math is right that's an over-subscription of 2.5:1 but generally it will be higher than that for cable (usually around 10:1) or DSL (probably 40:1 or 100:1). Fiber is usually good at around 5:1 or less but they can go higher, it's just a matter of how many people will hit the line at the same time.