Ok, just to clarify a couple of points, a 3-minute ADSL crash course in
some relevant points only:
* The subscriber lines used for ADSL are simply the already existing
phone lines. This usually is one twisted pair per subscriber (with a 1:1
mapping of a line to a phone number). This means that the subscriber, or
their house, has exclusive access to this line, which goes from the
house to the local exchange. As ADSL uses the same wire pair, the number
of users on this "line" is simply the number of users connecting via the
ADSL router, and it sounds like that is "an apple ipad and an oldish PC"
in this case... not much by the sounds of it.
* However, these twisted pair lines are bundled into bundle cables of
something like 25 or 50 twisted pairs to physically keep them together
on their way to the local exchange, with just the right number of
twisted pairs branching out at the right spot to get to the properties
where the connections are required (obviously you can get several lines
for one house if you want). Now these bundle cables are designed to
minimise cross-coupling and interference between the twisted pairs. BUT,
these cables were designed with telephony in mind, where the signal
bandwidth is limited by filters to 4 kHz. Now ADSL uses a band that
starts with its lower end at several kHz above the telephone band to
provide a sufficient "safety margin", so that voice and DSL signals can
easily be separated by inserting a cheap splitter filter (these filters
often come with ADSL routers). But the ADSL band goes up to frequencies
just over 1 MHz! And this is way more than what these cables were
designed for... So you do get a bit of cross-coupling and interference
between twisted pairs that are next to each other within these bundle
cables. How much of a problem that is depends on various parameters,
including cable length, wire gauge, and on which other pairs in the same
bundle other people are using ADSL as well. (It is worthwhile noting
that, even without interference, a long line will perform noticeably
worse for ADSL than a short one. Also, thicker wire gauge helps to
minimise problems with long lines. But the lines are as they are, and
Telecom are not going to replace several kms of bundle cable just to get
a few more kbps of ADSL throughput...)
* I would expect that the usual line testing when a customer first
complains about ADSL problems would be a pretty quick check taking only
a few seconds to run, and this would establish that:
- all relevant components of the local exchange (including the Digital
Subscriber Line Access Multiplexer = DSLAM) are working, and
- there actually is a line from the local exchange to the customer's
premises, and
- that that line is physically intact all along the way and does not
have any significant measurable defects over its entire length, and
- possibly that an ADSL router is connected to the customer end of the line.
That is all the ISP are responsible for, and once that is ascertained
any possible faults would then be the customer's to resolve. But in this
case here, it sounds like probably all of the above may be given (maybe
check and confirm?), however there is a quality of service issue. And in
order to get some traction on this, I can only second Craig's suggestion
to request some more thorough testing, with a specific view towards
highlighting the potential of cross-coupling or interference from other
users in the neighbourhood.
There is one further point to check: how are the computers accessing the
router? Ethernet cable? Or WiFi? If they are using WiFi, the there
obviously is a very real and fairly likely possibility that something
"is wrong" with the WiFi. And this also includes interference from the
neighbours. WiFi has been know to suffer from bandwidth degradation due
to interference for quite a while, and this is mainly an issue in
densely populated areas, but I can certainly tell when the neighbours
are active here in South Brighton...
To get back on topic slightly, on the WiFi side I am finding wavemon
useful - it runs on a text terminal using pretty minimal resources and
provides helpful real-time information on WiFi performance that helps a
lot to sort out antenna location problems etc.
Hope this helps somehow... let us know when you find out what was
causing the trouble!
Kind regards,
Helmut.
On 17/06/14 07:42, dave lilley wrote:
anyone here able to suggest anyway of testing number of
users connected to a line?
Mate who lives in Downs Rd South eyreton commented to me
about his link going down and he thinks too many people are
on it up stream.
mate says he spoke to the provider (not sure who it is) but
think they claimed the link was ok, I was hoping to nip out
using a linux lappie and test the line for some more solid
answers, They use an apple ipad and an oldish PC.
thanks for tips of many.
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