[154949] in North American Network Operators' Group
RE: Managing free pairs to prevent DSL sync. loss
daemon@ATHENA.MIT.EDU (John Souvestre)
Tue Jul 17 10:17:33 2012
From: "John Souvestre" <johns@sstar.com>
To: "'Anurag Bhatia'" <me@anuragbhatia.com>,
"'NANOG Mailing List'" <nanog@nanog.org>
In-Reply-To: <CAJ0+aXZWpomGXcm_TKQJxOt4S8emm2JaLXTCY+8tb4fpK0nfHg@mail.gmail.com>
Date: Tue, 17 Jul 2012 09:15:59 -0500
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Hello Anurag.
I have not heard of this problem before, but I imagine that the
non-terminated pairs could be acting like antennas and picking up noise.
Have you considered grounding one end (or both) of the free pairs? =
Perhaps
this would reduce the amount of noise they pick up.
Regards,
John
=A0=A0=A0 John Souvestre - New Orleans LA - (504) 454-0899
-----Original Message-----
From: Anurag Bhatia [mailto:me@anuragbhatia.com]=20
Sent: Tuesday, July 17, 2012 5:19 am
To: NANOG Mailing List
Subject: Managing free pairs to prevent DSL sync. loss
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.
Thanks.
--=20
Anurag Bhatia
Web: anuragbhatia.com
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