Bonded SDSL (was RE: ITU G.992.5 Annex M - ADSL2+M Questions)

Steve Bertrand steve at
Tue Jan 5 08:58:54 UTC 2010

Michael Sokolov wrote:
> Frank Bulk - <frnkblk at> wrote:
>> We offer it, but practically speaking we haven't gotten much higher than 1.5
>> Mbps on the upstream.
> Sorry that I'm coming into this thread late (I have just subscribed),
> but since I see people discussing DSL with beefy upstream, I thought I
> would be brave and ask: do you esteemed high-end network op folks think
> that there may be anyone in the world who might be interested in bonded
> SDSL or not?
> I have spent the past 5 years of my life learning everything there is to
> know about SDSL.  Don't ask me why, I don't really know the answer to
> that question myself.  I won't waste the bandwidth of this elite list
> with dirty details of just what I've done with SDSL over the past 5 y,
> but I'll give a link to an open source project that contains the body of
> SDSL knowledge amassed over those years:


I'm but a small humble ISP. We have sold SDSL since ~1996. The bonded
circuits have been terminated differently over the years, but I still
have a fair number of business clients that have SP supplied CPE that is
extremely affordable, and that require little to no work on our part.

Other than a few stragglers that I keep afloat on SDSL that require
fail-over, I've been trying to get rid of the dedicated copper as much
as possible, since I 'lease' the copper for the dry circuit(s).

We've reached past the break-even point for fibre access within our
area, and am at the point where the *very* 'ritzy' resi clients can and
will soon be approached.

The max length of SDSL that I currently have is 6.7 wired km. Bonded,
our longest distance is 5.4 km. Peak throughput over our longest bonded
(2 pair) SDSL circuit is 2.25Mb.

Given relative average, in the locations that I can provide optics,
there is a gain of revenue percentage that I achieve over standard
copper SDSL.

IOW, when revenue for a bonded SDSL circuit is $285 and I pay $49.40 per
circuit for the four wire copper, things begin to look more attractive
when I pay *nothing* for the dark fibre, but am able to provide multiple
times the bandwidth at the same price to the client ;)

fwiw, for bonded SDSL, we have currently:

- Symmetric GoWide units deployed (both on the PE and CPE) that
inherently manage two-pair which requires but one switch port and no
configuration. Aggregates internally.

- an 'Elastic' rack that requires a bit more setup on both ends.
Terminate into a vlan on a switch to aggregate properly. A 'setup' fee
covers this one-time fix. Remember, small ISP, I'm not used to scaling
human resources ;)

- multiple other stand-alone SDSL modem types (dslam/non-dslam, such as
PairGain etc)

- Copper Mountain

BTW, while on topic, if you know anyone who wants a fully shelved and
carded Copper Mountain CE200 dslam w/ dual power supplies, let me know ;)


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