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Re: What is multihoming was (design of a real routing v. endpoint id seperation)
Thus spake <Michael.Dillon@btradianz.com>
AFAICT, that is the accepted definition in this forum. Anything less is best called by a different, more precise term to avoid confusion.> the market wouldn't > feel the need to have to dual home.the internet model is to expect and route around failure.Seems to me that there is some confusion over the meaning of "multihoming". We seem to assume that it means BGP multihoming wherein a network is connected to multiple ASes and uses BGP to manage traffic flows.
That is virtual hosting in a NANOG context. Some undereducated MCSEs might call it multihoming, but let's not endorse that here.Other people use this term in very different ways. To some people it means using having multiple IP addresses bound to a single network interface. To others it means multiple websites on one server.
I bet customers who bought two links to Cogent no longer believe they're "multihomed"; policy failures are disturbingly frequent in Tier 2s, particularly those wanting to join the Tier 1 club. Total network failures are rarer, but even folks like UUNET, WorldCom, AT&T, MCI, etc. have them from time to time. With restoral times measured in days on both types of occasions, you can't discount them as "extremely unlikely" if your business can't function without a network. Ask the folks at Starbucks how many millions of dollars of coffee they gave away when their cash registers didn't work for a couple days... and how many customers (i.e. future revenue) they would have lost if they hadn't.A single tier-2 ISP who uses BGP multihoming with several tier 1 ISPs can provide "multihoming" to it's customers without BGP. For instance, if this tier-2 has two PoPs in a city and peering links exist at both PoPs and they sell a resilient access service where the customer has two links, one to each PoP, then it is possible to route around many failures. This is probably sufficient for most people and if the tier-2 provider takes this service seriously they can engineer things to make total network collapse exteremely unlikely.
Two links to the same provider is merely "redundancy" or "link/POP diversity", not multihoming. Don't let your marketing department override your common sense or engineering clue.
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