Managing free pairs to prevent DSL sync. loss

Anurag Bhatia me at
Tue Jul 17 10:18:43 UTC 2012

Hello everyone.

I am having some very bad time due to my ISP's poor last mile (in India).
DSL is loosing sync. consistently and this time problem seems quite
interesting so I though to ask how ISPs across world managing it. Problem
is high attenuation & low SNR because of "lot of free pairs" in the cable.
My connection is coming from something like 100 pair >  50 pair > 20 pair >
5 pair. Now 100 pair has less then 30 active lines but based on testing it
seems like at 100 pair DP there's very low noise and everything is pretty
good (usual BSNL pillars in India have 100 pair terminations). Next 20 pair
has just 4 active lines (and 16 free lines causing issues for those 4
working lines) and at the end my line comes from 20 > 5 with only one
(which is my) line active on one of 5 pairs.

Now argument of my ISP (BSNL) is that due to excessive number of free
pairs, they are causing huge noise and they likely need to reduce these
DP's by putting 1-2 line wire from my home till 100 pair pillar termination
(which is down in other street and so needs effort in digging and putting
new wire). But I just never heard about this problem anywhere else. Do DSL
providers really suffer due to free pairs? Assuming other pairs are all
crossed/shorted, can they still produce significant noise in other working
lines? Also, what exactly was "bonding" used by AT&T in US? I thought it
was actually making use of free pairs, bonding them together and having
more bandwidth for end user, isn't it?

If someone can pass me some detailed whitepaper or document explaining
about this noise, it will be very much helpful.



Anurag Bhatia

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