This is more “home networking” than “homelab,” but I imagine the people here might be familiar with what in talking about.
I’m trying to understand the logic behind ISPs offering asymmetrical connections. From a usage standpoint, the vast majority of traffic goes to the end-user instead of from the end-user. From a technical standpoint, though, it seems like it would be more difficult and more expensive to offer an asymmetrical connection.
While consumers may be connected via fiber, cable, DSL, etc, I assume that the ISP has a number of fiber links to “the internet.” Those links are almost surely some symmetrical standard (maybe 40 or 100Gb). So if they assume that they can support 1000 users at a certain download speed, what is the advantage of limiting the upload? If their incoming trunks can support 1000 users at 100Mb download, shouldn’t it also support 1000 users at 100Mb upload since the trunks themselves are symmetrical?
Limiting the upload speed to a different rate than download seems like it would just add a layer of complexity. I don’t see a financial benefit either; if their links are already saturated for download, reducing upload speed doesn’t help them add additional users. Upload bandwidth doesn’t magically turn into download bandwidth.
Obviously there’s some reason for this, but I can’t think of one.
Upload bandwidth doesn’t magically turn into download bandwidth
Actually, it does. Various Cable and DSL standards involve splitting up a big (eg, measured in MHz) band of the spectrum into many small (eg, around 4 or 8 kHz wide) channels which are each used unidirectionally. By allocating more of these channels to one direction, it is possible to (literally) devote more band width - both the kinds measured in kilohertz and megabits - to one of the directions than is possible in a symmetric configuration.
Of course, since the combined up and down maximum throughput configured to be allowed for most plans is nowhere near the limit of what is physically available, the cynical answer that it is actually just capitalism doing value-based pricing to maximize revenue is also a correct explanation.
You are absolutely correct; I phrased that badly. Over any kind of RF link, bandwidth is just bandwidth. I was more referring to modern ethernet standards, all of which assume a separate link for upload and download. As far as I am aware, even bi-directional fiber links still work symmetrically, just different wavelengths over the same fiber.
If you have a 10GBaseT connection, only using 5Gb in one direction doesn’t give you 15Gb in the other. It’s still 10Gb either way.
You are being obtuse. Fiber and cable and DSL are not “ethernet standards” and Ethernet is not used for last mile connections. Re-read the excellent explanation.
Ethernet is used last mile all the time. Fibre is just the medium. Wide area networks use many protocols, ethernet is very common. See MAN for some more context.
Apart from the technical reasons already mentioned, before things like Twitch and TikTok and Instagram were a thing, people mostly downloaded content and very rarely uploaded much. So it made sense for the ISPs to allocate more downstream channels and advertise much higher download speeds which is what everyone cared about. Especially with DSL and aging copper lines, it kind of tops out at 40-50 Mbps for most people when lucky (even though VDSL2-Vplus technically can go up to 300/100). Especially if you’re shoving IPTV on that line, 25/25 is much less desirable for the average consumer than say, 45/5.
And as others have said, it’s much easier for the ISP to throw more power on your lines to sustain faster speeds, so it just kind of happened that it was convenient for everyone to do it that way.
It also has the side effect of heavily discouraging hosting servers at home, reduces the amount of bandwidth used by torrenting and the likes.
Cable does this because of the inherit bandwidth restrictions it comes with, along with being able to price gouge customers to pay for faster upload. Coax (really, DOCSIS) and the related infrastructure around it simply does not have the bandwidth to offer symmetric connections, at least for companies like Comcast (yuck). They will wait until it’s absolutely necessary to upgrade their infrastructure to support faster upload. Even then, it likely will not be symmetric since there needs to be channels for TV/phone too.
Fiber has much more bandwidth, and the related infrastructure does too. That’s why it’s almost always symmetric.
