[Hizonner]

A cable that's carrying traffic for 30,000 subscribers is "backbone" enough. I don't expect redundant paths to my block, but 30,000 is a big enough area that it's reasonable to expect it not to be knocked out by single, reasonably likely events. Even for power, which is much, much more expensive to make redundant, single transmission lines that can knock out that many people should be rare.

Let's not normalize bad behavior here.

[justapassenger]

Oakland is fairly densely populated urban area. 30k subscribers is roughly an area of 3 sq miles. It's normal for any type of infrastructure service not have redundancy for it.

I hate Comcast as much as most other people, but this is not something I can blame them for. It's a reasonably sized area for last mile service.

[Hizonner]

So, I got interested, and I took some time and asked around and did some research.

According to somebody on /r/Grid_Ops, normal practice is for every single electrical substation to have redundant incoming feeds.

PG&E's "Local Capacity Area Substation List" lists 33 substations in Oakland. Wikipedia says that the population of Oakland is 440,000. So that's about 13,500 subscribers per substation (rounding up). I imagine the size varies, and some of those substations are probably dedicated to big industrial users. So let's say the bigger ones are more than double the average size and serve 30,000 subscribers.

That means that the utility is, in fact, providing redundant transmission lines at the scale of 30,000 subscribers. In fact, on the average they're probably providing redundancy at a much smaller scale than that. That's in spite of the fact that electrical power line redundancy is many times more expensive than data line redundancy. Running a 115kV feed for a substation is a whole different kind of project from running a fiber bundle.

But we're not done. That 30,000 is what you'd lose if the whole substation went out, but a substation is much better protected than a cable. To get to something comparable to this fiber case, we need to ask how many people losing any single cable might take out. That's much less than 30,000 or even 13,500, because a substation has a lot more than one downstream line, and those downstream lines are independent of one another. Losing any one of them doesn't knock out every subscriber of the substation.

I'm still unsure about that number, but from what I've seen it looks like it'd be more like 5000 at the absolute maximum, if a line got hit right next to the substation. If it got hit after some branching had happened, it would be much less than that.

It's less clear, but another person on /r/Grid_Ops suggested that they'd think of anything over 15MW as a "major outage", in a context that seemed to imply that "major outages" were the sort of thing you'd expect to have redundancy to prevent. I'm again not completely sure, but I get the impression that that's around 3000 residential subscribers.

So, no, it is not "normal" for "any type of infrastructure" service not to have redundancy for three densely populated square miles.

[iptrans]

It may be normal, but it’s still poor engineering practice.

[alar44]

Thinking you can just buy 2 of everything is poor engineering practice. That's almost never practical. Engineering is about balancing reliability with other factors, not just over designing things.

Then again, maybe you're right, and you're the first person to come up with this idea.

[iptrans]

This is a straw man.

Physical path redundancy for backhaul and/or feeders does not require two of everything, merely that you close the loop.