My experience with these issues (as a customer):
I have a corp lan and space in 6 colo's around the US. Connectivity between
corp and the colo's is mission critical. Initially this was addressed by
two T1's each from different providers and we advertised a /24 for the corp.
This was hugely benficial b/c just prior to one of the providers imploding
problems arose with the circuit that they could not manage to resolve with
the telco (probably b/c they weren't paying their bills). Data could still
get down the line at a poor rate and I was able to maintain it as a backup
to the good circuit until another was provisioned. I was able to do this
effectively and quickly b/c I had a measure of control over my routing.
I intended to get the 2nd circuit from another provider, but my existing
(good) provider asked for the opportunity to convince me otherwise. They
happen to be a smallish, local ISP and I happen to deal directly with one of
their principals who is an excellent network engineer. He came in and made
one of the most detailed and lucid proposals I have ever seen from a vendor.
The bottom line was, I have one fiber access into the building. Nothing to
be done from me to the CO. But, he was able to get me a 2nd circuit through
Worldcom (first being Verizon) take it to another POP which is in-turn
connected to a different set of carriers than the other. "Oh, and by the
way, this 2nd circuit with us will be dirt cheap." Sold, with caution. I
still maintain a BGP session to him and advertise the /24. Why? If this
turns out not to have been such a great idea, I can cancel that 2nd circuit,
go back to plan A, with minimal re-engineering. If things continue to run
smoothly for another 6 to 12 months, then maybe I'll feel confident enough
to turn over all routing control to him.
My points: We have colo'd as much as possible, but in the end we still have
a critical need to reach those facilities. Maitaining an EBGP session and
advertising a non-aggregated block gives me control and flexibility.
However, the right provider can possibly provide another solution. We
should see more providers marketing this and maybe I wouldn't be so
cautious. But, a big part of why I was even willing to experiment with this
was what I felt to be the quality of engineering on the ISP's side and total
understanding of the situation I was in (in addition to having direct access
to their knowledgable, senior staff at any hour). This is, in my
experience, simply not the norm and an ISP customer is forced to take the
matter into their own hands.
Hope I haven't been too redundant, but half my time is spent as exactly the
type of customer you're all discussing.
Why are customers spending money on this? My belief is that they
want more say in their own fate. That may express itself as
a desire for redundancy in the case of catastrophic business failures,
better ability to express their own routing policies, or a simple
worry that they won't get the best price if they have only one supplier.
At the core of this, though, is a desire for more control over something
that they see as increasingly important to their own fate.
I'm at a multi-POP network in Boston. We've had great luck selling
customers a Verizon circuit into one of our POPs and a Worldcom circuit
into a different one. It costs more, but they don't have nearly the
exposure of a single circuit customer. However, if you're not set up to
do this, the appropriate level of paranoia calls for circuits to two
different providers. Maybe if SPs really addressed availability
requirements of their customers, it wouldn't be such an issue.