Why isn't ADSL rate adaptive

Out of curiosity can anyone throw
any light on why after a short burst
of noise, your ADSL speed is significantly
reduced, and takes a long time, which can
be one or more days, to recover.
The initial reduction of profile I can
understand, speed is reduced until the
error rate makes best use of the line.
A slower connection with a stable 10% error
rate being better than a faster connection
with a 98% error rate, the latter spending
most of the time error correcting and
retransmiting errored blocks/packets.
What I can't understand is why when the
noise burst ends, and it may only last
a few seconds or less, your former
faster speed is not quickly restored,
within a few minutes rather than after
one or more days, even though thoughout
this time your modem/router is showing
a steady 15 or 16db SNR.

(E-Mail Removed) wrote:

> Out of curiosity can anyone throw
> any light on why after a short burst
> of noise, your ADSL speed is significantly
> reduced, and takes a long time, which can
> be one or more days, to recover.
> The initial reduction of profile I can
> understand, speed is reduced until the
> error rate makes best use of the line.
> A slower connection with a stable 10% error
> rate being better than a faster connection
> with a 98% error rate, the latter spending
> most of the time error correcting and
> retransmiting errored blocks/packets.
> What I can't understand is why when the
> noise burst ends, and it may only last
> a few seconds or less, your former
> faster speed is not quickly restored,
> within a few minutes rather than after
> one or more days, even though thoughout
> this time your modem/router is showing
> a steady 15 or 16db SNR.

Uh ?

I thought modern ADSL IS RADSL.

Graham

> Out of curiosity can anyone throw
> any light on why after a short burst
> of noise, your ADSL speed is significantly
> reduced, and takes a long time, which can
> be one or more days, to recover.
> The initial reduction of profile I can
> understand, speed is reduced until the
> error rate makes best use of the line.
> A slower connection with a stable 10% error
> rate being better than a faster connection
> with a 98% error rate, the latter spending
> most of the time error correcting and
> retransmiting errored blocks/packets.
> What I can't understand is why when the
> noise burst ends, and it may only last
> a few seconds or less, your former
> faster speed is not quickly restored,
> within a few minutes rather than after
> one or more days, even though thoughout
> this time your modem/router is showing
> a steady 15 or 16db SNR.

The simple answer is that the BT adaptive system is poorly designed, poorly
implemented and based on an ultra-conservative model. Quite simply it not
fit for the purpose it is intended for but as BT has a de facto monopoly we
are stuck with it. AIUI when BT implement ADSL2+ it should improve.

Peter Crosland

Peter Crosland wrote:

> The simple answer is that the BT adaptive system is poorly designed, poorly
> implemented and based on an ultra-conservative model. Quite simply it not
> fit for the purpose it is intended for but as BT has a de facto monopoly we
> are stuck with it. AIUI when BT implement ADSL2+ it should improve.

You mean 'Max' is a poor implementatation of RADSL ?

Graham

Stupid BT has changed the way it works.
Since January my line is stuck on 12dB SNR though it worked pretty well on
6db and less before that !

Its like this:
BT sells you a car that will do 'up to' 80 mph.
In reality it will at best reach 28 mph, and the engine cuts out every few
days, if not hours.
Instead of fixing the problem, BT reduces the speed to 17 mph,
but of course it still cuts out just the same !

In real life one could get a new car or the money back,
but BT is still a monopoly and law to itself !

BT are UNNECESSARILY reducing the usability of our connection.

We now have mobile broadband, as yet it's not any better, but is meant to
improve soon. We may be giving up broadband and the BT line.....
Regards,
Martin

"Martin²" wrote:

> Stupid BT has changed the way it works.
> Since January my line is stuck on 12dB SNR though it worked pretty well on
> 6db and less before that !
>
> Its like this:
> BT sells you a car that will do 'up to' 80 mph.
> In reality it will at best reach 28 mph, and the engine cuts out every few
> days, if not hours.
> Instead of fixing the problem, BT reduces the speed to 17 mph,
> but of course it still cuts out just the same !
>
> In real life one could get a new car or the money back,
> but BT is still a monopoly and law to itself !
>
> BT are UNNECESSARILY reducing the usability of our connection.
>
> We now have mobile broadband, as yet it's not any better, but is meant to
> improve soon. We may be giving up broadband and the BT line....

Who's your ISP ?

Chances are ALL the trouble lies there and I do mean 'lies'.

Graham

On Wed, 02 Jul 2008 21:02:06 +0100, Eeyore passed an empty day by writing:

> (E-Mail Removed) wrote:
>
>> Out of curiosity can anyone throw
>> any light on why after a short burst
>> of noise, your ADSL speed is significantly reduced, and takes a long
>> time, which can be one or more days, to recover.
>> The initial reduction of profile I can understand, speed is reduced
>> until the error rate makes best use of the line. A slower connection
>> with a stable 10% error rate being better than a faster connection with
>> a 98% error rate, the latter spending most of the time error correcting
>> and retransmiting errored blocks/packets. What I can't understand is
>> why when the noise burst ends, and it may only last a few seconds or
>> less, your former
>> faster speed is not quickly restored, within a few minutes rather than
>> after one or more days, even though thoughout this time your
>> modem/router is showing a steady 15 or 16db SNR.
>
> Uh ?
>
> I thought modern ADSL IS RADSL.
>
> Graham

AFAIR Graham you are spot on. The 'fixed' speeds we once had
(512/1024/2048) were capped in software. ADSL 'Max' or RADSL removed
these fixed settings and let the hardware make the decisions.

Any DSL that has the ability to change speed due to line conditions is,
by nature, rate adaptive.


--
begin oefixed_in_2005.exe

On 03 Jul 2008 06:43:23 GMT, Klunk <(E-Mail Removed)> wrote:

>On Wed, 02 Jul 2008 21:02:06 +0100, Eeyore passed an empty day by writing:
>
>> (E-Mail Removed) wrote:
>>
>>> Out of curiosity can anyone throw
>>> any light on why after a short burst
>>> of noise, your ADSL speed is significantly reduced, and takes a long
>>> time, which can be one or more days, to recover.
>>> The initial reduction of profile I can understand, speed is reduced
>>> until the error rate makes best use of the line. A slower connection
>>> with a stable 10% error rate being better than a faster connection with
>>> a 98% error rate, the latter spending most of the time error correcting
>>> and retransmiting errored blocks/packets. What I can't understand is
>>> why when the noise burst ends, and it may only last a few seconds or
>>> less, your former
>>> faster speed is not quickly restored, within a few minutes rather than
>>> after one or more days, even though thoughout this time your
>>> modem/router is showing a steady 15 or 16db SNR.
>>
>> Uh ?
>>
>> I thought modern ADSL IS RADSL.
>>
>> Graham
>
>AFAIR Graham you are spot on. The 'fixed' speeds we once had
>(512/1024/2048) were capped in software. ADSL 'Max' or RADSL removed
>these fixed settings and let the hardware make the decisions.

Oh that it were so. BT Wholesale's network manager for ADSL Max
actually makes the decisions.

>Any DSL that has the ability to change speed due to line conditions is,
>by nature, rate adaptive.

Subject to the above.

On Wed, 2 Jul 2008 21:28:38 +0100, "Peter Crosland"
<(E-Mail Removed)> wrote:

>> Out of curiosity can anyone throw
>> any light on why after a short burst
>> of noise, your ADSL speed is significantly
>> reduced, and takes a long time, which can
>> be one or more days, to recover.
>> The initial reduction of profile I can
>> understand, speed is reduced until the
>> error rate makes best use of the line.
>> A slower connection with a stable 10% error
>> rate being better than a faster connection
>> with a 98% error rate, the latter spending
>> most of the time error correcting and
>> retransmiting errored blocks/packets.
>> What I can't understand is why when the
>> noise burst ends, and it may only last
>> a few seconds or less, your former
>> faster speed is not quickly restored,
>> within a few minutes rather than after
>> one or more days, even though thoughout
>> this time your modem/router is showing
>> a steady 15 or 16db SNR.
>
>The simple answer is that the BT adaptive system is poorly designed, poorly
>implemented and based on an ultra-conservative model. Quite simply it not
>fit for the purpose it is intended for but as BT has a de facto monopoly we
>are stuck with it. AIUI when BT implement ADSL2+ it should improve.
>

I think the conservatism might be down to ISPs (by which I mean BT
Retail) needing something as stable as possible for services like BT
Vision that need a decent level of network QoS.

If you know a line has found its long-term average level, as an ISP
trying to deliver services critically dependent on stability that's
precisely what you want.

I imagine a line flapping around with its sync trying to support IPTV.
I'm not saying it's right or wrong, I'm merely suggesting why it's
been done that way.

On Wed, 2 Jul 2008 19:48:17 GMT, (E-Mail Removed) wrote:

>Out of curiosity can anyone throw
>any light on why after a short burst
>of noise, your ADSL speed is significantly
>reduced, and takes a long time, which can
>be one or more days, to recover.
>The initial reduction of profile I can
>understand, speed is reduced until the
>error rate makes best use of the line.
>A slower connection with a stable 10% error
>rate being better than a faster connection
>with a 98% error rate, the latter spending
>most of the time error correcting and
>retransmiting errored blocks/packets.
>What I can't understand is why when the
>noise burst ends, and it may only last
>a few seconds or less, your former
>faster speed is not quickly restored,
>within a few minutes rather than after
>one or more days, even though thoughout
>this time your modem/router is showing
>a steady 15 or 16db SNR.

It can take up to 5 days to recover.

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