ADSL Modem link performance indicators?

Hi,

I've looked many times on the net for some form of ADSL modem
performance indicators for a given line conditions and so far I've
found none.

Like many others, have poor line conditions and I'm lucky to get 1.5
mbit/sec.

I'd be happy to pay a extra for a modem that gave me a bit more, may
be 2 mbit/sec or more.

So far the only modem I've seen that (sort of) promises more are from
Zoom.

http://www.zoom.com/products/adsl_overview.html

Zooms claim may be just marketing hype - my question is how do you
tell?

Cheers, Steve

(E-Mail Removed) wrote:
> Hi,
>
> I've looked many times on the net for some form of ADSL modem
> performance indicators for a given line conditions and so far I've
> found none.
>
> Like many others, have poor line conditions and I'm lucky to get 1.5
> mbit/sec.
>
> I'd be happy to pay a extra for a modem that gave me a bit more, may
> be 2 mbit/sec or more.
>
> So far the only modem I've seen that (sort of) promises more are from
> Zoom.
>
> http://www.zoom.com/products/adsl_overview.html
>
> Zooms claim may be just marketing hype - my question is how do you
> tell?
>
> Cheers, Steve

To be honest, performance is critically related to the line SNR.

Almost all routers seem to be able to synch reliably at 6db SNR..now my
D-link before I found the magic switch was syncing at only 3.5dB..but
that made it supremely flakey - any extra line noise and it crapped out.

As far as shaving the extra few db's - is it worth it? you will trade
speed for frequency of resyncs, and the far end may well decide to
insist you go slower anyway..the chipsets are all from maybe half a
dozen types, an there isn't a lot you can do to make them better than
they are.

Unless you have a very BAD router, I doubt that changing will make a
deal of difference.

"The Natural Philosopher" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> (E-Mail Removed) wrote:
>> Hi,
>>
>> I've looked many times on the net for some form of ADSL modem
>> performance indicators for a given line conditions and so far I've
>> found none.
>>
>> Like many others, have poor line conditions and I'm lucky to get 1.5
>> mbit/sec.
>>
>> I'd be happy to pay a extra for a modem that gave me a bit more, may
>> be 2 mbit/sec or more.
>>
>> So far the only modem I've seen that (sort of) promises more are from
>> Zoom.
>>
>> http://www.zoom.com/products/adsl_overview.html
>>
>> Zooms claim may be just marketing hype - my question is how do you
>> tell?
>>
>> Cheers, Steve
>
> To be honest, performance is critically related to the line SNR.
>
> Almost all routers seem to be able to synch reliably at 6db SNR..now my
> D-link before I found the magic switch was syncing at only 3.5dB..but that
> made it supremely flakey - any extra line noise and it crapped out.<<



As a D-Link owner I have to ask, what 'magic switch'?

national treasure wrote:

> "The Natural Philosopher" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> (E-Mail Removed) wrote:
>>> Hi,
>>>
>>> I've looked many times on the net for some form of ADSL modem
>>> performance indicators for a given line conditions and so far I've
>>> found none.
>>>
>>> Like many others, have poor line conditions and I'm lucky to get 1.5
>>> mbit/sec.
>>>
>>> I'd be happy to pay a extra for a modem that gave me a bit more, may
>>> be 2 mbit/sec or more.
>>>
>>> So far the only modem I've seen that (sort of) promises more are from
>>> Zoom.
>>>
>>> http://www.zoom.com/products/adsl_overview.html
>>>
>>> Zooms claim may be just marketing hype - my question is how do you
>>> tell?
>>>
>>> Cheers, Steve
>>
>> To be honest, performance is critically related to the line SNR.
>>
>> Almost all routers seem to be able to synch reliably at 6db SNR..now my
>> D-link before I found the magic switch was syncing at only 3.5dB..but
>> that made it supremely flakey - any extra line noise and it crapped
>> out.<<
>
> As a D-Link owner I have to ask, what 'magic switch'?

Are we talking about ADSL Max?

With fixed rate services, the ADSL modem is informed by the DSLAM what line
rate to train up at, irrespective of line conditions. Rate adaptive
services are designed to allow the DSLAM and the modem to negotiate the
optimum speed between a maximum and minimum rate using a parameter called
target margin.

The target margin is the required signal to noise ratio needed to keep the
line in synchronisation and it is this parameter that DLM flexes to optimise
the rate and stability. By increasing the target margin, DLM can force the
line to take more margin and therefore make it more immune to noise
variations. Without this dynamic control, a static value would have to be
selected, with the consequence that many lines would run slower than
required and others less stable.

During rate adaptation, the modem has to measure the line characteristics
and agree a downstream rate with the DSLAM for a given target margin. If
the modem is bad at measuring margin, then the line can either run too
conservatively or too aggressively depending on whether the modem
underestimates, or overestimates the margin respectively.

As the modems and DSLAM negotiate the parameters that control the rate
adaptation process, it is possible for the modem to manipulate the margin
and rate that the line runs at.

In skilled hands, adjustment could lead to an improvement in performance,
but in general it is a rather risky practice for two reasons. Firstly, the
software needs to tweak the DSL chipset in the modem and any mistakes in
this configuration could cause serious stability issues. Secondly this
bypasses DLM, which is designed to resolve stability issues and could cause
very serious performance issues.

Much better to look at the sate of your internal home wiring and make sure
it's as good as possible.

--
Arecibo

national treasure wrote:
> "The Natural Philosopher" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> (E-Mail Removed) wrote:
>>> Hi,
>>>
>>> I've looked many times on the net for some form of ADSL modem
>>> performance indicators for a given line conditions and so far I've
>>> found none.
>>>
>>> Like many others, have poor line conditions and I'm lucky to get 1.5
>>> mbit/sec.
>>>
>>> I'd be happy to pay a extra for a modem that gave me a bit more, may
>>> be 2 mbit/sec or more.
>>>
>>> So far the only modem I've seen that (sort of) promises more are from
>>> Zoom.
>>>
>>> http://www.zoom.com/products/adsl_overview.html
>>>
>>> Zooms claim may be just marketing hype - my question is how do you
>>> tell?
>>>
>>> Cheers, Steve
>> To be honest, performance is critically related to the line SNR.
>>
>> Almost all routers seem to be able to synch reliably at 6db SNR..now my
>> D-link before I found the magic switch was syncing at only 3.5dB..but that
>> made it supremely flakey - any extra line noise and it crapped out.<<
>
>
>
> As a D-Link owner I have to ask, what 'magic switch'?
>
>
This is an OLD DSL-504

Using telnet, the answer proved to be 'itex enhance 0'

Followed by the commands to save it into memory and into flash memory.

with enhance 1, it wanted to sync at over 6Mbps...despite what the other
end said. Now its down around 4Mbps...and is responding to the BT kit's
shaping profiles as expected.

Here is the full command set.
substiute your local router IP address as appropriate

#telnet 192.168.0.254

Trying 192.168.0.254...
Connected to 192.168.0.254.
Escape character is '^]'.
password: <private>
logged on; type `@close' to close connection.
192.168.0.254> itex
192.168.0.254 itex> enhance 0
Change will have no permanent effect after restart unless you config save.
192.168.0.254 itex> home
192.168.0.254> config save
Saving configuration...Configuration saved.
192.168.0.254> itex line down
Deactivating line...
192.168.0.254> itex line up
192.168.0.254> flashfs update
Updating Flash filing system ...
done
192.168.0.254> @close


As far as I can tell "itex enhance 1" is the default setting. It plays
merry hell with the line discovery algorithm that BT use.

Arecibo wrote:
> national treasure wrote:
>
>> "The Natural Philosopher" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed)...
>>> (E-Mail Removed) wrote:
>>>> Hi,
>>>>
>>>> I've looked many times on the net for some form of ADSL modem
>>>> performance indicators for a given line conditions and so far I've
>>>> found none.
>>>>
>>>> Like many others, have poor line conditions and I'm lucky to get 1.5
>>>> mbit/sec.
>>>>
>>>> I'd be happy to pay a extra for a modem that gave me a bit more, may
>>>> be 2 mbit/sec or more.
>>>>
>>>> So far the only modem I've seen that (sort of) promises more are from
>>>> Zoom.
>>>>
>>>> http://www.zoom.com/products/adsl_overview.html
>>>>
>>>> Zooms claim may be just marketing hype - my question is how do you
>>>> tell?
>>>>
>>>> Cheers, Steve
>>> To be honest, performance is critically related to the line SNR.
>>>
>>> Almost all routers seem to be able to synch reliably at 6db SNR..now my
>>> D-link before I found the magic switch was syncing at only 3.5dB..but
>>> that made it supremely flakey - any extra line noise and it crapped
>>> out.<<
>> As a D-Link owner I have to ask, what 'magic switch'?
>
> Are we talking about ADSL Max?

Yes.

>
> With fixed rate services, the ADSL modem is informed by the DSLAM what line
> rate to train up at, irrespective of line conditions. Rate adaptive
> services are designed to allow the DSLAM and the modem to negotiate the
> optimum speed between a maximum and minimum rate using a parameter called
> target margin.
>
> The target margin is the required signal to noise ratio needed to keep the
> line in synchronisation and it is this parameter that DLM flexes to optimise
> the rate and stability. By increasing the target margin, DLM can force the
> line to take more margin and therefore make it more immune to noise
> variations. Without this dynamic control, a static value would have to be
> selected, with the consequence that many lines would run slower than
> required and others less stable.
>
> During rate adaptation, the modem has to measure the line characteristics
> and agree a downstream rate with the DSLAM for a given target margin. If
> the modem is bad at measuring margin, then the line can either run too
> conservatively or too aggressively depending on whether the modem
> underestimates, or overestimates the margin respectively.
>
> As the modems and DSLAM negotiate the parameters that control the rate
> adaptation process, it is possible for the modem to manipulate the margin
> and rate that the line runs at.
>
> In skilled hands, adjustment could lead to an improvement in performance,
> but in general it is a rather risky practice for two reasons. Firstly, the
> software needs to tweak the DSL chipset in the modem and any mistakes in
> this configuration could cause serious stability issues. Secondly this
> bypasses DLM, which is designed to resolve stability issues and could cause
> very serious performance issues.

Absolutely. That is precisely what I found. That is why I had to turn
this OFF. It appeared to be on by default in my router - previously used
on a fixed rate service with no problems.

I got the speeds OK..but any twitch on the line caused a resynch. Horrible.


>
> Much better to look at the sate of your internal home wiring and make sure
> it's as good as possible.
>

Sure. eliminate that first.. (I did) but in the end its the line to you
that is the limiting factor, not the router and not the microfilter, as
long as its all 'good enough'

My own (unwanted) experience shows that tweaking up the router is
basically a waste of time. You trade speed for unacceptable resynch rates.

I am now on a rock solid BRAS of 3Mbps instead of an ultra flakey
4.5Mbps.I may have gone too far in fact, as I have a high noise margin
set at the exchange due to the original router setting I used.. I have
been monitoring resynchs, and may well ask the ISP to get that reduced a
notch.

"national treasure" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
<snip>
>
> As a D-Link owner I have to ask, what 'magic switch'?
>

i consigned my dlink 604t to the bin, and replaced it with a netgear 834gt
with much better results

tony h wrote:
> "national treasure" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
> <snip>
>> As a D-Link owner I have to ask, what 'magic switch'?
>>
>
> i consigned my dlink 604t to the bin, and replaced it with a netgear 834gt
> with much better results
>
>
The 604t was not a partcularly good model from what i have read.

"The Natural Philosopher" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> tony h wrote:
>> "national treasure" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed)...
>> <snip>
>>> As a D-Link owner I have to ask, what 'magic switch'?
>>>
>>
>> i consigned my dlink 604t to the bin, and replaced it with a netgear
>> 834gt with much better results
> The 604t was not a partcularly good model from what i have read.<<


Sod's law, of course, decrees that mine *is* the 604T (G604T)

I'm not sure whether your \Telnet tip is applicable to my set up - but what
are the main shortcomings of the 604?

My only real problem was the need to bypass the DNS cache because it fills
up - and then chokes the router. Setting it to look for the DNS at every
connection solved that one.

I understand that the 604 chipset (can't remember the manufacturer) is one
of the better ones at handling noisy lines?

national treasure wrote:
> "The Natural Philosopher" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> tony h wrote:
>>> "national treasure" <(E-Mail Removed)> wrote in message
>>> news:(E-Mail Removed)...
>>> <snip>
>>>> As a D-Link owner I have to ask, what 'magic switch'?
>>>>
>>> i consigned my dlink 604t to the bin, and replaced it with a netgear
>>> 834gt with much better results
>> The 604t was not a partcularly good model from what i have read.<<
>
>
> Sod's law, of course, decrees that mine *is* the 604T (G604T)
>
> I'm not sure whether your \Telnet tip is applicable to my set up - but what
> are the main shortcomings of the 604?
>
> My only real problem was the need to bypass the DNS cache because it fills
> up - and then chokes the router. Setting it to look for the DNS at every
> connection solved that one.
>

Don't use it for DNS THEN!!!

I run BIND on a linux box and configure the local machines to use that.
Or you my find later firmware fixes all that..

> I understand that the 604 chipset (can't remember the manufacturer) is one
> of the better ones at handling noisy lines?
>

Can't recall offhand to be honest. Not my area of expertise.

>