ADSL Bandwidth Monitoring

Tim Daneliuk tundra at
Sat Sep 8 13:27:50 PDT 2007

Amitabh Kant wrote:
> On 9/8/07, Bahman M. <b.movaqar at> wrote:
>> I tested the connection by downloading 2~3 files simultaneously and used
>> 'bmon' as Mel suggested in another reply (thanks to him).  As I'd
>> already guessed the RX don't get bigger than 30~40% of the expected
>> bandwidth.  I performed the test with some other files and there was no
>> difference.
>> Thanks,
>> Bahman
> The bandwidth being advertised by your ISP would be the maximum
> thoughput allowed on your DSL lines with multiple DSL users sharing
> the same bandwidth, something that is generally known as contention
> ratio.
> See this link:
> Amitabh

But you should be able to hit the advertised bandwidth.  To the best
of my knowledge, DSL itself is NOT a shared medium.  It is a point-to-
point technology from your premise to the Central Office.  The
bandwidth *behind* the CO may be shared, but should be so large
as to not be a bottleneck.   My provider (Speakeasy) advertises
1.5/384 ADSL for my circuit and that is *exactly* what I get whether
moving a single file or multiple files simultaneously.

There are only two reasons I can think of that would prevent you
from hitting full advertised bandwidth:

1) You are too far away from the CO to hold up the circuit a full speed.
    Most DSL bridges/routers are adaptive and will downshift to a speed
    where the error rate is reduced to an acceptable level.  Even if
    you are not far away from the CO, you will also see this if the copper
    pair is noisy for some other reason: bad grounding, bad splicing, old
    wire, etc.

2) Your premise wiring is hosed.  Home telephone wiring is typically
    utter crap for data, even on newer homes.   A new run of Cat 3 cable
    directly from the Network Interface box on the side of the building
    to the jack where the DSL bridge plugs in can do wonders.  Also make
    sure that the cable from the bridge to that jack is good - I just had
    one go bad and wreak havoc for a while in my office.


Tim Daneliuk     tundra at
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