On 01/03/2015 03:41, Barry Shein wrote:
On February 28, 2015 at 23:20 nick@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