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.
A part of it is because technology, specially a decade or so ago, had restrictions. Like with ADSL which often/always couldn't support higher upload speeds due to the end user hardware, and the same goes with 4/5G today, your cellphone just doesn't have the power to transmit as fast/far as the tower access point.
But with wired connections, specially with fibre/coax, that doesn't apply and money comes in to play. ISPs pay for the bandwidth to the 'next step' on the network. Your 'last mile' ISP buys some amount of traffic from the 'state wide operator' (kind-of, depends heavily on where you live, but the analogy should work anyways) and that's where the "upload" and "download" traffic starts to play a part. I'm not an expert by any stretch here, so take this with a spoonful of salt, but the traffic inside your ISP's network and going trough their hardware doesn't cost 'anything' (electricity for the switches/routers and their maintenance is excluded as a cost of doing business) but once you push additional 10Gbps to the neighboring ISP it requires resources to manage that.
And that (at least in here) where the asymmetric connections plays a part. Let's say that you have a 1Gbps connection to youtube/netflix/whatever. The original source needs to pay for the network for the bandwidth for your stream to go trough in order to get a decent user experience. But the traffic from your ISP to the network is far less, a blunt analogy would be that your computer sends a request to the network 'show me the latest Me. Beast video' and youtube server says 'sure, here's a few gigabits of video'.
Now, when everyone pays for the 'next step' connection by the actual amount of data consumed (as their hardware needs to have the capacity to take the load). On your generic home user profile, the amount downloaded (and going trough your network) is vastly bigger than the traffic going out of your network. That way your last mile ISP can negotiate with the 'upstream' operator to have capacity to take 10Gbps in (which is essentially free once the hardware is purchased) and that you only send 1Gbps out, so 'upstream' operator needs to have a lot less capacity going trough their network to 'the other way'.
So, as the link speeds and amount of traffic is billed separately, it's way more profitable to offer 1Gbps down and 100Mbps up for the home user. This all is of course a gross simplification of everything and in real world things are vastly more complex with caching servers, multiple connections to the other networks and so on, but at the end every bit you transfer has a price and if you mostly offer to sink in the data your users want and it's significantly less than the data your users push trough to the upstream there's money to be made in this imbalance and that's why your connection might be asymmetric.