On 01/03/2015 03:41, Barry Shein wrote: > On February 28, 2015 at 23:20 n...@foobar.org (Nick Hilliard) wrote: > > there were several reasons for asymmetric services, one of which was > > commercial. Another was that most users' bandwidth profiles were massively > > asymmetric to start with so it made sense for consumers to have more > > bandwidth in one direction than another. > > How could they have known this before it was introduced?
because we had modem banks before we had adsl. > I say that was prescriptive and a best guess that it'd be acceptable > and a way to differentiate commercial from residential > service. Previously all residential service (e.g., dial-up, ISDN) was > symmetrical. Maybe they had some data on that usage but it'd be muddy > just due to the low bandwidth they provided. maybe it was symmetric on your modems; it wasn't on the modems I managed. > Another still was that cross-talk > > causes enough interference to prevent reverse adsl (i.e. greater bandwidth > > from customer to exchange) from working well. > > So SDSL didn't exist? SDSL generally maxes out at 2mbit/s and can be run near adsl without causing problems, but that's not what I was talking about. If you were to run a 24:1 adsl service with the dslam at the customer side, it will cause cross-talk problems at the exchange end and that would trash bandwidth for other adsl users in the exchange->customer direction. > Anyhow, *DSL is falling so far behind it's > difficult to analyze what could have been. not really no. Spectral analysis is clear on efficiency measurement - we know the upper limits on spectral efficiency due to Shannon's law. > > > As were bandwidth caps. > > > > Bandwidth caps were introduced in many cases to stop gratuitous abuse of > > service by the 1% of users who persistently ran their links at a rate that > > the pricing model they selected was not designed to handle. You've been > > around the block a bit so I'm sure you remember the days when transit was > > expensive and a major cost factor in running an isp. > > It was the combination of asymmetric, no or few IPs (and NAT), and > bandwidth caps. let's not rewrite history here: IPv4 address scarcity has been a thing since the very early 1990s. Otherwise why would cidr have been created? > Sure. once it became institutionalized and the market got used to it > why not sell tiered bandwidth services at different price points, but > that could have been true of symmetrical service also. my point is simply that there is often more to asymmetric services than extracting more money from the customer. Nick
