Date   : Sun, 18 Oct 2009 18:52:19 +0100
From   : robert@... (Rob)
Subject: [OT] ADSL capabilities

On 18/10/2009, Rick Murray <rick@...> wrote:
> Hi,
>
> I am looking for advice.

It might be worth asking on the thinkbroadband.com forums - it's a
UK-centric site, but I imagine the technicalities are about the same.

>
> My Livebox (a Livebox Mini/Sagem, if it matters) is connected to a phone
> line. There is no traditional phone, it is broadband only with the phone
> via VoIP.

I wish we had that option; over here, we have to rent telephone
service as well..


> Various websites quote the line as being about 4.4km. I can walk from
> the house to a big green box by the Mayor and it is around 2.5km. Unless
> the "real exchange" is hiding in the forest, that's *IT*.

How big a green box? Normally exchanges are fairly large - even the
smallest village's would be about the size of a double garage.  It's
possible it's just a fancy Distribution Point, with the exchange some
way away along a hefty multi-pair cable.


> I was told that my original wish, 8mbit, was not possible because of
> where I lived. I then, a few weeks later, had to specify exactly where I
> lived, which makes me dubious as to whether they just said that because
> I'm "not in a town" or if anybody actually bothered to check.

LOL.

>
> So I have 1mbit.
>
> The livebox diagnostics reports:
>
>   1.14 Att?nuation Up (dB)                      : 21,1 dB
>   1.15 Att?nuation Down (dB)                    : 49,8 dB
>   1.16 Signal bruit Up (dB)                     : 2,0 dB
>   1.17 Signal bruit Down (dB)                   : 11,0 dB

These are significant for your question:
>   1.18 D?bit maximum possible ligne Up (kb/s)   : 952 kb/s
>   1.19 D?bit maximum possible ligne Down (kb/s) : 4132 kb/s


>   1.20 Puissance ?mise (dBm)                    : 12,5 dBm
>   1.21 Puissance re?ue (dBm)                    : 15,3 dBm
>
> My current measured is around 980-1300 kb/s upload, and about 265 kb/s
> download. I have noticed on the odd time my download when running
> FreeDownloadManager (and thus grabbing a large file in chunks) actually
> whizzes past the 1mbit limit, not by much, but it does.

It looks like the line is syncing up at around 4Mbps towards you, but
you are being software-throttled to 1Mbps at the ISP.   It's not
unusual, I've seen it happen over here (a 256Kbps cheap account synced
at 2Mbps.)  It saves your ISP having to do anything but change a speed
setting on your account, rather than having the teleco upgrade the
connection.

>
> In the very beginning, the quality was rubbish and dropped out a lot. I
...
> Anyway, after some hiccups, the service has been a reliable megabit.

Sounds normal - most modern exchange equipment spends the first couple
of weeks or so on a new connection gradually stepping down the maximum
sync speed and monitoring the number of errors, and it then sets
itself a limit just below some threshold whereby you should get the
best speed (no use packets coming through 50% faster if it has to
re-send every one!)

>
> I am assuming that if I ask to be converted to 8mbit, it will throttle
> back to something that works - thus around 4mbit. I would be perfectly
> happy with this as it will be four times faster for the same price.
> After all, I *am* in the country here!

Yep.  I get about 5Mbs on one of the "up to 8Mbs" lines here, 6+ on the other..

> But the big question - do I stand to lose? I mean, is 1mbit and 8mbit
> the same thing, only with a speed restriction? Is there some sort of
> technical difference where the 8mbit version will not step back to
> ~1mbit but would just shut down instead?

Not given those figures - you're already talking to the exchange at
4Mpbs or thereabouts.

>
> Is it worth asking for an upgrade to 8mbit (=4mbit for me), or should I
> stay with 1mbit?

I would say yes, given the costs are the same.

HTH.

Rob.