|
North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical What is multihoming was (design of a real routing v. endpoint id seperation)
> > 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. 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. And to many consumers of network access it is a synonym for redundancy or resiliency or something like that. BGP multihoming is not the only way to satisfy the consumers of network access and design a solution in which failure is expected and it is possible for the customer to route around failure. 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. Another way in which consumer's could be "multihomed" would be to have their single access link going to an Internet exchange where there is a choice of providers. If one provider's network fails, they could phone up another provider at the exchange and have a cross-connect moved to restore connectivity in an hour or so. This will satisfy many people. Of course there are many variations on the above theme. This is an issue with multiple solutions, some of which will be superior to BGP multihoming. It's not a simple black or white scenario. And being a tier-1 transit-free provider is not all good. It may give some people psychological comfort to think that they are in the number 1 tier, but customers have good reason to see tier-1 transit-free status as a negative. --Michael Dillon
|