garethrobinson1 said:
I'm talking about BT's configuration of ADSL circuit profiles on DSLAM ports.
I'm talking about generic ADSL. Rate adaption's a well defined process, it's just taken BT this long to catch up.
A standard DSL circuit will have a margin of say 35dB in or very close to the exchange and then decrease as line quality degrades and noise is introduced. (Under the current DSL speed profiles, the margin is set to the maximum possible to keep the noise clear of the ADSL frequencies.)
The target SNR margin is the same - the difference is that the downstream sync rate is currently tied (so the SNR margin will vary with how "good" the line is). With the Max services, the tie's removed, so the pair will push as hard as they can (with the control of the DLM kit for "stability").
"Keeping the noise clear of the ADSL frequencies" is the modem/DSLAM's job, and should continue to happen with MaxDSL - the only difference being that both should be aiming for as close to 100% occupation as (stably) possible.
If you think every line's sitting at an SNR margin of 35dB, you better get busy sending engineers out (to a few million lines). Doubt you'll ever see an SNR margin that high (and certainly not on any more than single digits of percent).
The DSL MAX profile fixes the margin to 6dB initally and increases it if noise begins to creep in.
The other way round. The sync rate is reduced to maintain the SNR margin above the target. "If noise begins to creep in", the SNR drops, so the sync rate is reduced (and correspondingly the stable rate will reduce).
All standard ADSL/G.DMT stuff.
I won't go into too much detail but changing from 35dB to 6dB allows 'BINs' to be freed up and the circuit can then take advantage of these extra BINs to increase the overall line speed / bandwidth.
Not quite. The bins always existed (and weren't necessarily occupied either), the modem just never used them (or used a reduced bit rate for each bin). The only way you're going to get full sync/ATM rate is 100% occupation, so shock horror, more bins occupied, and more bits per bin.
Higher bin number == higher frequency == lower SNR, so higher occupation of those bins gives a reduced SNR. No surprises there.
I don't know EmoHawk and don't read ADSLguide forums
Oh well. I'll keep my skeptic hat on then.
I've been supporting DSL MAX for BT Wholesale since the trials started (& xDSL for 6 years) so I know this from experience.
Broadband
Assurance Tech Support?
The 500kbps change is carried out on the RAS, even though the actual line sync speed will actually be around 500kbps - 1000kbps faster. For example, a circuit syncing at 6000kbps (between modem & DSLAM port) is actually throttled at 5000kbps on the RAS.
Curious, especially given the ISPs have (some) control over the "payload rate" (to use the STIN's terms), and it's not mentioned in (any) of the S(T)INs either (SIN 386 and STIN441, both version 2, for the interested).
Yes, during the initial 10 day period. It has to do this to calculate the MSR and FTR.
Odd that no one is warning about this (but are taking orders for IPStream Max). The STIN warns:
BT said:
These lines will then be re-configured automatically (if possible) to give an improvement in their overall ADSL performance and stability. This re-configuration will result in a short break (typically 20 seconds) in end user service.
Which sounds like it'll kick you off and rate adapt downwards if your connection becomes unstable, but nothing about kicking you off (on a regular basis) to "calculate the MSR and FTR".
However, the DSL MAX profile is applied, which compared to the current DSL profiles is a different kettle of fish altogether
A profile isn't a port change...
One thing's for sure, there's plenty FUD spreading about the Max services.
CurlyWhirly said:
For the first 10 days while the 'bedding-in' period is taking place, is it going to be quite normal to be disconnected regularly as the line limits are reached or is this unlikely to happen?
The
official sources certainly aren't saying that.
You might get kicked off as part of normal SNR margin variation (ie you'll find your SNR margin drops about 1800 hours, and comes back up ~0600), but they ain't saying you'll be regularly kicked off to work out a maximum stable rate.
There's the bit I quoted, or you can go read them for yourself on
SINet. The numbers I mentioned earlier are the two you're looking for (or just search for "Max").