Re: redundancy [was: something about arrogance]

[David Schwartz <davids () webmaster com>]

On Tue, 30 Jul 2002 03:23:24 -0700, Pedro R Marques wrote:

> All of those are much more frequent than the failure of an entire ISP (a
> transit provider). It is expected, i believe, of a competent ISP to
> provide redudancy both within a POP and intra-POP links/equipment and
> its connections to upstreams/peers.

        Yes, but when the ISP that all your redundant links go to and that you got
all your IPs from goes out of business, what's the mean time to repair? 30
days?

> So, my question to the list is, why is multi-homing to 2 different
> providers such a desirable thing ? What is the motivation and why is it
> prefered over multiple connections to the same upstream ?

        You cannot as easily be held hostage. I have consulted for a few ISPs and
have my share of war stories.

        Here's a (true!) example. One day, a certain head of a fairly large ISP
decided that he wouldn't route traffic to or from IPs he had assigned that
didn't reverse resolve because he felt it was imperative that people be able
to find network contacts in this way (I think he got sick of being the one to
get the abuse emails). He told my client three days before implementing a
sweep and filter. He had the equivalent of about 38 /24s from this ISP
distributed over about 180 customers, they were his sole uplink.

        Here's another good one. A client needed a /22 immediately for a major
customer about to come online, set it up fast or lost the account. We made
sure to met all the IP assignment guidelines and our justification was
impeccable, we had >90% utilization of a /18. The only problem was, the
client's provider had a screw up in their allocations and justifications and
their applications were being refused by ARIN until they fixed their
problems. Now what?

        One more just for kicks. Client had a 100Mbps circuit from their sole
provider (100Mbps to colocated router, DS3 from this router to their
premises). The circuit had been in place for several years and the contract
had long since expired. One day, they got a call -- they had 5 days to agree
to a new (and MUCH higher) pricing scheme with a much higher minimum paid
bandwidth amount or their circuit would be turned off. The kicker -- they had
to agree to a two year term!

        The other issue is provider misconfigurations/meltdowns. They're not common,
but if you're multihomed, you can just shut down the circuit to the
misconfigured providers. There have been a few cases of these that I've seem
where the repair time was several hours.

        If you add cases where just one POP was out, the number goes way up. If
you're only in one location yourself and only use one provider, all of your
redundant links will likely go to the same POP.

        DS