Failover how much complexity will it add?

John.Herbert at ins.com John.Herbert at ins.com
Sun Nov 8 12:09:11 CST 2009


Seth Mattinen [sethm at rollernet.us] said:

>Forget all of that and just multihome to two separate providers with BGP
--Assuming that you're advertising PI space or can work around that appropriately with your providers, I agree, that's the ideal situation.

>Having multiple circuits to one provider *will not* back anything up if that provider
>has an outage as they are %99.999 likely to be part of the same larger circuit 
--True - if you don't specify otherwise when you're ordering, then why would they make the effort? Comments made in some of the other responses in this thread are also valid even with a single service provider - diverse entry points into your facility, diverse upstream circuit routing, and homing to different POPs - which may mean backhauling your secondary circuit away from your local POP and taking a hit for the higher latency on that second link. The moral of this is that whether you're using one provider or more than one, state your diversity requirements clearly up front, and then stay involved and make sure that what's presented to you is _actually_ diverse (oldsflash: even the best intentioned people sometimes make mistakes, especially when there's a handoff to a different last mile provider who may not have been clear on the requirement ). Of course, all of this is potentially wasted effort if the data center you're providing connectivity for does not also maintain the same kind of diversity itself in terms of power, connectivity, architecture, etc.

>and certainly share the same infrastructure at the provider.
--If you enter a single provider's network at diverse points, then that local infrastructure isn't the same at least. But by the same measure, if that provider has a major BGP issue for example, then yeah - they're both screwed... in which case we loop back to the dual provider scenario you mentioned in the first place :)

Ultimately choosing the appropriate solution will boil down to the what level of service unavailability one can tolerate in the first place, and put a business value on that impact. From that one can derive technical options, then go cap in hand with a business case to the poor soul paying the bill ;-)

j.



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