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Klunk
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 Posted: Fri Jul 04, 2008 12:44 am Post subject: Re: Why isn't ADSL rate adaptive |
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"Martin" <never@give.one> wrote in message
| Quote: |
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.....
|
George Weston wrote in message
Enter stage left the mobile phone mast campaigners - you know the ones,
don't want masts near the school but give the kids mobile phones to take
to school and expect them to work. You know the ones who moan about slow
broadband, and then object to the mast that could give them fast wireless
broadband . . .
Where is my soap box . . .
--
begin oefixed_in_2005.exe |
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The Natural Philosopher
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| Posted: Fri Jul 04, 2008 12:53 am Post subject: Re: Why isn't ADSL rate adaptive |
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ato_zee@hotmail.com wrote:
| Quote: |
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.
|
resynch your router. It wil come up fast and relaible.
HOWEVERE beware teh dreaded BRAS profile. BT doesn't buffer in its
DSLAMS so they will lower the BRAS rate to the lowest rate you have been
ables to sustain for a period.
That WILL take days to recover from. |
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Invalid
Guest
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| Posted: Fri Jul 04, 2008 3:30 am Post subject: Re: Why isn't ADSL rate adaptive |
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|
In message <Iz2bk.63078$Kb.7850@newsfe29.ams2>, ato_zee@hotmail.com
writes
| Quote: |
On 3-Jul-2008, "Mortimer" <me@privacy.net> wrote:
It can take up to 5 days to recover.
Which is precisely the point that the OP was making: it takes a long time
to
recover from a brief period of noise.
Exactly, I'm the original poster, and find
it takes a few days to recover from a short
burst of noise, even though my router
log shows a consistent 15.5db SNR.
I'm with Zen, and although well regarded,
they cannot fully fill the pipe, but that
is the "up to" fact of life that we
all suffer from.
What tee's me off is how long it takes
to recover.
Only solution I've found, which helps a
little is to swap Draytek and BT modems.
This seems to force two retrains, the
second when I put the original one back
again.
After a few hours, to several days later
sync rate drops again.
I suspect that BT is deliberately using
conservative settings so that connections
are slower and disadvantaged against their
own product.
My modem is next to the BT NTE5, no
extension phones or wiring, in an
electrically quiet area, quality filter,
and no SNR change when I unplug the
phone. From the router it's CAT5.
This thread seems to be confusing at least three issues. |
1)The speed at which the OP's router is currently connected.
2)The speed at which it would reconnect if rebooted
3)The BRAS profile speed.
As I understand it
1) Once the router has connected at a particular speed it will not
change unless it looses sync or is forced to do so by one end or the
other. In that sense ADSL is not dynamically rate adaptive, but does so
in steps. Once the router has lost sync due to a noise burst and
renegotiated a lower speed at reconnection (because the line is still
noisy) its speed will not recover again until another disconnection
occurs. A reboot when the line noise improves should get the speed back
immediately (subject to 2 below). Under these circumstances the router
will resync at 6dB or thereabouts
2) On a resync ADSLMax attempts to connect the line at a target noise
level (SNR) usually 6 dB.That establishes the speed at which it
resync's. If the line has a history of frequent disconnects (more than
10 in a 1 hour period?) the BT kit will increase the target SNR in steps
to improve the lines stability. Once the SNR has been increased in this
way it apparently takes several days or weeks of stable running before
the target SNR is reduced again. (An ISP can get BT to change it
manually). Under these circumstances the OP's router would resync at 9,
12 or 15 dB each time it was rebooted.
3) BT set a BRAS speed, the maximum rate at which the ISP sends data.
This is (at least 500k?) lower than the stable rate for the link to
avoid buffering & retransmission in the BT network. This appears to
change every few hours. (daily?) depending on the stable speed of the
line.
I monitor my router using Routerstats (freeware). I am 4 km from the
exchange, all overhead wiring. During the day the SNR sits at 6 plus or
minus and the speed at 6250ish. Just before sunset it rises by 1 or 2dB
for a couple of hours. At sunset it drops down to only 1 or 2 dB and
goes back up to 6 or 7dB at sunrise. My router often looses sync at
11-12 pm when the noise level gets bad, and resyncs at 5800ish. If it
does drop out overnight, I reboot in the morning and it all goes back to
6250/6dB. A couple of days with no dropout at night and I get a 5500
BRAS. After a couple of noisy nights it drops to 5000.
As I read this post, the OP has something very like my line. Occasional
drops due to noise bursts, but is waiting for another random event or
swapping routers to trigger a resync. The question is what happens if
the OP just reboots after the noise clears. I would expect the speed to
recover.
--
Invalid |
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MartinČ
Guest
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| Posted: Fri Jul 04, 2008 7:59 am Post subject: Re: Why isn't ADSL rate adaptive |
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Invalid
| Quote: |
As I read this post, the OP has something very like my line. Occasional
drops due to noise bursts, but is waiting for another random event or
swapping routers to trigger a resync. The question is what happens if the
OP just reboots after the noise clears. I would expect the speed to
recover.
|
It used to, rebooting when the SNR got higher then 7 brought the speed back
up to my max 2.8Mb/s.
But now it wont ! It's stuck at 12dB which gives me 1.6 - 1.7Mb/s (but
actual dwnl speed just 800kb/s).
It almost never stays up for 5 days, REGARDLESS of what the min SNR is set
to.
I am going to try swapping routers, hopefully tomorrow.
Regards,
Martin |
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Klunk
Guest
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| Posted: Fri Jul 04, 2008 11:02 am Post subject: Re: Why isn't ADSL rate adaptive |
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|
On Fri, 04 Jul 2008 10:28:43 +0100, Eeyore passed an empty day by writing:
| Quote: |
Klunk wrote:
Invalid passed an empty day by writing:
In that sense ADSL is not dynamically rate adaptive
If I were being anal I would say that is not what he thread says. It
says 'Why isn't ADSL rate adaptive' - which it is.
Thinking out of the box, why should we consider this to be a wholly BT
issue? If you wait for them to get their act together then you'll
probably die waiting.
Look at it this way; if I drive my car and my radio signal is weak, I
retune. If I then find that signal weak after a while, I may again
retune. I don't wait for the radio station to move the mast.
So, with this in mind, why can't the routers firmware pick up the fact
that the statistics on the line have changed, and then refresh the
sync? Surely this is a pretty basic thing to do in router firmware if
the vendors wanted to do it?
Am I missing something?
I thought that's what RADSL does. It works here.
Graham
|
Clue: look for a hint of sarcasm ;-)
--
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Eeyore
Guest
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| Posted: Fri Jul 04, 2008 11:02 am Post subject: Re: Why isn't ADSL rate adaptive |
|
|
Klunk wrote:
| Quote: |
Invalid passed an empty day by writing:
In that sense ADSL is not dynamically rate adaptive
If I were being anal I would say that is not what he thread says. It says
'Why isn't ADSL rate adaptive' - which it is.
Thinking out of the box, why should we consider this to be a wholly BT
issue? If you wait for them to get their act together then you'll
probably die waiting.
Look at it this way; if I drive my car and my radio signal is weak, I
retune. If I then find that signal weak after a while, I may again
retune. I don't wait for the radio station to move the mast.
So, with this in mind, why can't the routers firmware pick up the fact
that the statistics on the line have changed, and then refresh the sync?
Surely this is a pretty basic thing to do in router firmware if the
vendors wanted to do it?
Am I missing something?
|
I thought that's what RADSL does. It works here.
Graham |
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Klunk
Guest
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| Posted: Fri Jul 04, 2008 11:02 am Post subject: Re: Why isn't ADSL rate adaptive |
|
|
On Thu, 03 Jul 2008 23:30:49 +0100, Invalid passed an empty day by
writing:
| Quote: |
In that sense ADSL is not dynamically rate adaptive
|
If I were being anal I would say that is not what he thread says. It says
'Why isn't ADSL rate adaptive' - which it is.
Thinking out of the box, why should we consider this to be a wholly BT
issue? If you wait for them to get their act together then you'll
probably die waiting.
Look at it this way; if I drive my car and my radio signal is weak, I
retune. If I then find that signal weak after a while, I may again
retune. I don't wait for the radio station to move the mast.
So, with this in mind, why can't the routers firmware pick up the fact
that the statistics on the line have changed, and then refresh the sync?
Surely this is a pretty basic thing to do in router firmware if the
vendors wanted to do it?
Am I missing something? |
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WCZ
Guest
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| Posted: Fri Jul 04, 2008 11:03 am Post subject: Re: Why isn't ADSL rate adaptive |
|
|
MartinČ wrote:
| Quote: |
Invalid
As I read this post, the OP has something very like my line.
Occasional drops due to noise bursts, but is waiting for another
random event or swapping routers to trigger a resync. The question
is what happens if the OP just reboots after the noise clears. I
would expect the speed to recover.
It used to, rebooting when the SNR got higher then 7 brought the
speed back up to my max 2.8Mb/s.
But now it wont ! It's stuck at 12dB which gives me 1.6 - 1.7Mb/s (but
actual dwnl speed just 800kb/s).
It almost never stays up for 5 days, REGARDLESS of what the min SNR
is set to.
I am going to try swapping routers, hopefully tomorrow.
Regards,
Martin
|
I can't see where you've posted your router details but I used to use a
Netgear DG834v3 which held onto my connection come rain or shine. It would
even hold on down to 1db.
I'm now using a 2Wire 2700 which gives me a higher sync but I get more
resyncs and the occasional random reboot too.
If you're after something that will hang on to the line then I'd recommend
you try and get a Netgear. eBay has a bunch of Sky branded DG834GT
apparently going fairly cheap (can't check as eBay is filtered at work).
One of these gives you the added benenfit of being able to manuall tweak
your SNR. So even though you're currently at 12db the DMT tool or the
UberGT firmware should be able to give you something closer to 8 or maybe
less. You will need to reflash the firmware to get the Sky stuff off it but
thats a doddle.
--
WCZ |
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Alec
Guest
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| Posted: Fri Jul 04, 2008 9:46 pm Post subject: Re: Why isn't ADSL rate adaptive |
|
|
If your noise level changes at about sunset or sunrise this could be related
to radio interference and may be worst in the evening. Remember adsl works
on similar frequencies.
Remember the medium wave radio stations which were great in the evening,
well these are just the ones you do not want on your broadband line. Would
be worst on an overhead line.
Alec
"Invalid" <news@wisty.plus.com.invalid> wrote in message
news:9k4T9FIZMVbIFwWF@wisty.plus.com...
| Quote: |
In message <Iz2bk.63078$Kb.7850@newsfe29.ams2>, ato_zee@hotmail.com writes
On 3-Jul-2008, "Mortimer" <me@privacy.net> wrote:
It can take up to 5 days to recover.
Which is precisely the point that the OP was making: it takes a long
time
to
recover from a brief period of noise.
Exactly, I'm the original poster, and find
it takes a few days to recover from a short
burst of noise, even though my router
log shows a consistent 15.5db SNR.
I'm with Zen, and although well regarded,
they cannot fully fill the pipe, but that
is the "up to" fact of life that we
all suffer from.
What tee's me off is how long it takes
to recover.
Only solution I've found, which helps a
little is to swap Draytek and BT modems.
This seems to force two retrains, the
second when I put the original one back
again.
After a few hours, to several days later
sync rate drops again.
I suspect that BT is deliberately using
conservative settings so that connections
are slower and disadvantaged against their
own product.
My modem is next to the BT NTE5, no
extension phones or wiring, in an
electrically quiet area, quality filter,
and no SNR change when I unplug the
phone. From the router it's CAT5.
This thread seems to be confusing at least three issues.
1)The speed at which the OP's router is currently connected.
2)The speed at which it would reconnect if rebooted
3)The BRAS profile speed.
As I understand it
1) Once the router has connected at a particular speed it will not change
unless it looses sync or is forced to do so by one end or the other. In
that sense ADSL is not dynamically rate adaptive, but does so in steps.
Once the router has lost sync due to a noise burst and renegotiated a
lower speed at reconnection (because the line is still noisy) its speed
will not recover again until another disconnection occurs. A reboot when
the line noise improves should get the speed back immediately (subject to
2 below). Under these circumstances the router will resync at 6dB or
thereabouts
2) On a resync ADSLMax attempts to connect the line at a target noise
level (SNR) usually 6 dB.That establishes the speed at which it resync's.
If the line has a history of frequent disconnects (more than 10 in a 1
hour period?) the BT kit will increase the target SNR in steps to improve
the lines stability. Once the SNR has been increased in this way it
apparently takes several days or weeks of stable running before the target
SNR is reduced again. (An ISP can get BT to change it manually). Under
these circumstances the OP's router would resync at 9, 12 or 15 dB each
time it was rebooted.
3) BT set a BRAS speed, the maximum rate at which the ISP sends data. This
is (at least 500k?) lower than the stable rate for the link to avoid
buffering & retransmission in the BT network. This appears to change every
few hours. (daily?) depending on the stable speed of the line.
I monitor my router using Routerstats (freeware). I am 4 km from the
exchange, all overhead wiring. During the day the SNR sits at 6 plus or
minus and the speed at 6250ish. Just before sunset it rises by 1 or 2dB
for a couple of hours. At sunset it drops down to only 1 or 2 dB and
goes back up to 6 or 7dB at sunrise. My router often looses sync at
11-12 pm when the noise level gets bad, and resyncs at 5800ish. If it
does drop out overnight, I reboot in the morning and it all goes back to
6250/6dB. A couple of days with no dropout at night and I get a 5500 BRAS.
After a couple of noisy nights it drops to 5000.
As I read this post, the OP has something very like my line. Occasional
drops due to noise bursts, but is waiting for another random event or
swapping routers to trigger a resync. The question is what happens if the
OP just reboots after the noise clears. I would expect the speed to
recover.
--
Invalid |
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Klunk
Guest
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| Posted: Fri Jul 04, 2008 11:52 pm Post subject: Re: Why isn't ADSL rate adaptive |
|
|
On Fri, 04 Jul 2008 17:46:07 +0100, Alec passed an empty day by writing:
| Quote: |
If your noise level changes at about sunset or sunrise this could be
related to radio interference and may be worst in the evening. Remember
adsl works on similar frequencies.
Remember the medium wave radio stations which were great in the evening,
well these are just the ones you do not want on your broadband line.
Would be worst on an overhead line.
Alec
"Invalid" <news@wisty.plus.com.invalid> wrote in message
news:9k4T9FIZMVbIFwWF@wisty.plus.com...
In message <Iz2bk.63078$Kb.7850@newsfe29.ams2>, ato_zee@hotmail.com
writes
On 3-Jul-2008, "Mortimer" <me@privacy.net> wrote:
It can take up to 5 days to recover.
Which is precisely the point that the OP was making: it takes a long
time
to
recover from a brief period of noise.
Exactly, I'm the original poster, and find it takes a few days to
recover from a short burst of noise, even though my router log shows a
consistent 15.5db SNR.
I'm with Zen, and although well regarded, they cannot fully fill the
pipe, but that is the "up to" fact of life that we
all suffer from.
What tee's me off is how long it takes to recover.
Only solution I've found, which helps a little is to swap Draytek and
BT modems. This seems to force two retrains, the second when I put the
original one back again.
After a few hours, to several days later sync rate drops again.
I suspect that BT is deliberately using conservative settings so that
connections are slower and disadvantaged against their own product.
My modem is next to the BT NTE5, no
extension phones or wiring, in an
electrically quiet area, quality filter, and no SNR change when I
unplug the
phone. From the router it's CAT5.
This thread seems to be confusing at least three issues.
1)The speed at which the OP's router is currently connected.
2)The speed at which it would reconnect if rebooted
3)The BRAS profile speed.
As I understand it
1) Once the router has connected at a particular speed it will not
change unless it looses sync or is forced to do so by one end or the
other. In that sense ADSL is not dynamically rate adaptive, but does
so in steps. Once the router has lost sync due to a noise burst and
renegotiated a lower speed at reconnection (because the line is still
noisy) its speed will not recover again until another disconnection
occurs. A reboot when the line noise improves should get the speed back
immediately (subject to 2 below). Under these circumstances the router
will resync at 6dB or thereabouts
2) On a resync ADSLMax attempts to connect the line at a target noise
level (SNR) usually 6 dB.That establishes the speed at which it
resync's. If the line has a history of frequent disconnects (more than
10 in a 1 hour period?) the BT kit will increase the target SNR in
steps to improve the lines stability. Once the SNR has been increased
in this way it apparently takes several days or weeks of stable
running before the target SNR is reduced again. (An ISP can get BT to
change it manually). Under these circumstances the OP's router would
resync at 9, 12 or 15 dB each time it was rebooted.
3) BT set a BRAS speed, the maximum rate at which the ISP sends data.
This is (at least 500k?) lower than the stable rate for the link to
avoid buffering & retransmission in the BT network. This appears to
change every few hours. (daily?) depending on the stable speed of the
line.
I monitor my router using Routerstats (freeware). I am 4 km from the
exchange, all overhead wiring. During the day the SNR sits at 6 plus
or minus and the speed at 6250ish. Just before sunset it rises by 1 or
2dB for a couple of hours. At sunset it drops down to only 1 or 2 dB
and goes back up to 6 or 7dB at sunrise. My router often looses sync
at 11-12 pm when the noise level gets bad, and resyncs at 5800ish. If
it does drop out overnight, I reboot in the morning and it all goes
back to 6250/6dB. A couple of days with no dropout at night and I get a
5500 BRAS. After a couple of noisy nights it drops to 5000.
As I read this post, the OP has something very like my line. Occasional
drops due to noise bursts, but is waiting for another random event or
swapping routers to trigger a resync. The question is what happens if
the OP just reboots after the noise clears. I would expect the speed to
recover.
--
Invalid
|
Does radio Luxembourg still broadcast on MW? Man, that used to swamp
everything out in the evening!
--
begin oefixed_in_2005.exe |
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Invalid
Guest
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| Posted: Sat Jul 05, 2008 12:08 am Post subject: Re: Why isn't ADSL rate adaptive |
|
|
| Quote: |
On Fri, 04 Jul 2008 17:46:07 +0100, Alec passed an empty day by writing:
If your noise level changes at about sunset or sunrise this could be
related to radio interference and may be worst in the evening. Remember
adsl works on similar frequencies.
Remember the medium wave radio stations which were great in the evening,
well these are just the ones you do not want on your broadband line.
Would be worst on an overhead line.
Alec
"Invalid" <news@wisty.plus.com.invalid> wrote in message
news:9k4T9FIZMVbIFwWF@wisty.plus.com...
I monitor my router using Routerstats (freeware). I am 4 km from the
exchange, all overhead wiring. During the day the SNR sits at 6 plus
or minus and the speed at 6250ish. Just before sunset it rises by 1 or
2dB for a couple of hours. At sunset it drops down to only 1 or 2 dB
and goes back up to 6 or 7dB at sunrise. My router often looses sync
at 11-12 pm when the noise level gets bad, and resyncs at 5800ish. If
it does drop out overnight, I reboot in the morning and it all goes
back to 6250/6dB. A couple of days with no dropout at night and I get a
5500 BRAS. After a couple of noisy nights it drops to 5000.
|
That was my assumption. I have 4 km of aerial!!!!
In fact it gets worse in long dry spells - presumably the cable sheath
dries out and its RF insulation capability falls.
Regards
--
Invalid |
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Gaz
Guest
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| Posted: Sat Jul 05, 2008 9:45 pm Post subject: Re: Why isn't ADSL rate adaptive |
|
|
Peter Crosland wrote:
| Quote: |
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
|
The Sky llu network seems quite impressive adapting though, with an
aggressive target snr. It gives me three meg on a line BT couldnt even get
to sync at 512.
Gaz |
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MartinČ
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| Posted: Mon Jul 07, 2008 7:19 am Post subject: Re: Why isn't ADSL rate adaptive |
|
|
Klunk:
| Quote: |
So, with this in mind, why can't the routers firmware pick up the fact
that the statistics on the line have changed, and then refresh the sync?
Surely this is a pretty basic thing to do in router firmware if the
vendors wanted to do it?
Am I missing something?
|
Yes, the BT DSLAM will NO longer play ball and just sticks to min SNR
prescribed by BRAS for that line.
Therefore I think that routers that can set their own min SNR will be of no
help.
Regards,
Martin |
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Guest
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| Posted: Mon Jul 07, 2008 11:04 am Post subject: Re: Why isn't ADSL rate adaptive |
|
|
| Quote: |
There is just one thing that gets my mind boggling in all of this. Say
your LLU ISP decide to lower the noise threshold to give you that 'faster
speed'. You've not actually changed the fact that the line is saturated
with 'x' amount of noise. It probably follows that you may have an
increase in bit rate, but surely the error rate will increase in
proportion making any actual increase in speed less than it may first
appear?
|
IMHO the correct way to manage the SNR threshold is do do
it adaptively, measure the error rate, if it is high say over 30%
reduce the sync rate, if it then drops below say 10% increase
the sync rate. Thus your error rate would change at a rate
set by the sampling period, say 5 minutes, and float between
10% and 30%. On short lines the rate would increase to
the maximum since noise would never reach 30% error
rate.
None of the drastically reduced speed for several days after
a short noise burst, for example when the street lights come
on.
Sync rate is of course the size of the pipe, less the ADSL
protocol overhead. Whether your ISP can fill the pipe is
another matter, you get what you pay for, an "Up to 8MB"
pipe is no good if your ISP can only deliver 500K at peak
times.
It is like turning on your tap and taking 10 minutes to
fill the kettle, and half a day to run a bath. |
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Klunk
Guest
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| Posted: Mon Jul 07, 2008 11:04 am Post subject: Re: Why isn't ADSL rate adaptive |
|
|
On Mon, 07 Jul 2008 03:19:45 +0100, Martin passed an empty day by writing:
| Quote: |
Klunk:
So, with this in mind, why can't the routers firmware pick up the fact
that the statistics on the line have changed, and then refresh the sync?
Surely this is a pretty basic thing to do in router firmware if the
vendors wanted to do it?
Am I missing something?
Yes, the BT DSLAM will NO longer play ball and just sticks to min SNR
prescribed by BRAS for that line.
Therefore I think that routers that can set their own min SNR will be of
no help.
Regards,
Martin
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There is just one thing that gets my mind boggling in all of this. Say
your LLU ISP decide to lower the noise threshold to give you that 'faster
speed'. You've not actually changed the fact that the line is saturated
with 'x' amount of noise. It probably follows that you may have an
increase in bit rate, but surely the error rate will increase in
proportion making any actual increase in speed less than it may first
appear?
--
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