There's a dsl and cable line going in here. Both are "highest available consumer grade" for whatever that's worth. In my case, that means claimed speeds of 1.5 down and 1.0 up on dsl, and 20 down and 2 up on cable.
The DSL is a dedicated connection to my ISP so nothing affects my speeds short of water in the phone lines. (which does happen) But upstream on dsl is almost always limited to about 66% of downstream, and that's a limit of the technology.
Cable on the other hand varies wildly in both up and down, because it's using a shared connection. Some nights my downstream has dropped below 4 on average. Upstream on cable is also limited by the technology - they assign channels of some sort for uploading, and others for downloading, and depending on the ratio they assign them in determines how much slower the up is compared to the down. And if a fifth of the people on my leg of the line are downloading or doing pay per view, my download speed tanks.
In either case, most consumers want downstream so they can download fast. They're not sending large files or data and so don't need upstream. Of course ppl like me that run mailserver and webserver need mainly upstream unfortunately.
Adding to my problems, upstream tends to cost. It's common for ISPs to offer different sets of speeds for up and down, where the highest cost packages offer no more downstream, but faster upstream. .256 or .384 is common for DSL upstream speed, even if you're getting the full 1.5 down. Cable is much worse in that respect, because the cable customers want blazing fast downloads and don't care much about upstream so they divvy up most of the channels to downstream. 10:1 ratio is common, which is what I have. Where my DSL is 3:2 because up does not compete with down. The ISP 'provisions' your modem, capping its upstream speeds, and they provision your downstream on their end. So its possible for your line to be able to go a lot faster than the hardware is using it.
Bridging connections like the ones here is technically possible but impractical, so the two lines have different IP blocks. Its easier to obtain a static IP address or range from DSL than from cable. In many respects, T1's are like DSL, but they always cost a lot more, but have guaranteed uptime. If your internet goes down, they start cutting you a check, so you are at least a high priority. Cable company at best will give you the month for free if you call and complain while you are down. DSL not much better that way, the phone company's always stingy because they have grown used to being a monopoly.
Just to reiterate, upstream costs a lot more than downstream. Not entirely sure why, but I think it's a cascade thing where the ISPs have to pay a lot more for the traffic leaving their network than for that coming in. And they just pass that cost on to you. Oh, and if you buy your own dsl or cable modem because they are leasing you a piece of crap, be prepared for them to offer you zero support if you are having a problem, and blame your hardware.
