[Gllug] Two Adsl Connections

[Russell Howe]

On Fri, May 20, 2005 at 12:13:39PM +0100, Peter Childs wrote:
>    I'm thinking of getting a second adsl connection at work for 
> reduntancy when and if one fails for what ever reason

I can only really think of two likely reasons for an ADSL line failing:

* A fault at the Exchange, which would affect all DSL circuits at that
  exchange
* A fault on the LNS you are connected to, affecting all users on that
  LNS

This precludes things that aren't line related, such as local power
supply outages, a fire in your building or your ISP's
routing/connectivity going up the spout.

Both seem to occur fairly often, and by getting a second ADSL
connection, unless it is terminated at a different exchange, you really
only seem to be protecting yourself against a faulty telephone wire (not
unknown - we had problems with an ISDN30 at work, which were resolved by
switching to another pair of wires in the same cable) or a problem with
the LNS you are connected to.

By getting the second ADSL line with a different ISP, you'd protect
yourself against problems with the LNS and problems local to a single
ISP, so that might just about get you to the point where it's worth it.

Most people I would assume, would get two ADSL lines in order to get
more than 256Kbit/s upstream. The best way to benefit when all you want
is speed seems to be to get bonded ADSL from someone like Nildram, or to
find one of the companies which offers LLU services (Easynet, for
example).

Once you start talking about multiple lines for redundancy, you are
really getting into the realms of wanting to run a multi-homed site,
with the temptation to try and get BGP peering going between you and the
ISP, but that's not going to come cheap (and possibly not even going to
come at all). It's also rather overkill and so complicated it may well
be less reliable than the single line!

One of the biggest enemies of reliability is complexity.

-- 
Russell Howe       | Why be just another cog in the machine,
rhowe at siksai.co.uk | when you can be the spanner in the works?
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