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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: FW: /8s and filtering
Hello, Now I am confused because I have got two sets of contradicting answers. Some say that anyone can multihome, some say that you need to be of a certain minimum size to multihome. May I know what is the right answer? I agree that allowing anyone to multihome would increase the size of the routing table. So does this mean that someone has to be of a certain size to multihome? Harsha. On Tue, 10 Dec 2002, David Schwartz wrote: > > > On Tue, 10 Dec 2002 12:36:39 -0600 (CST), Forrest wrote: > > >Maybe I'm missing something, but what good would it do for someone to > >multihome if only their own providers accept their route, but nobody else > >does? I realize that their block should be still announced with their > >ISP's larger aggregate, but what good does this do if your ISP goes down > >and can't announce the large aggregate. > > Smaller multihomers elect to multihome for a variety of reasons. Those > reasons typically include latency reduction and toleration of POP failures, > router failures, and line failures. They're not looking to stay online is > Sprint or MCI disappears entirely. > > If you multihomed to 2 providers in this manner and made a table of all your > downtime and its causes, loss of the larger aggregate would the tiniest > fraction of your downtime, which is already a tiny fraction of the time. > > We don't put parachutes on commuter jets. The failures where > these would be helpful are but the tineiest fraction of the failures that > occur. And any significant failure at all of such a redundant system is > rare. > > >If you're a smaller organization, perhaps you'll only have a /23 from your > >upstream provider. With the filtering that seems to be in place, it seems > >like the only way you can truly multihome with a /23 is if it happens to > >be in the old Class C space. Or is this wrong? > > You're just biasing the question with the choice of words you use ... > "truly" multihome. > > >What seems to be needed is perhaps a /8 set aside by the RIR specifically > >to allocate to small organizations that wish to multihome that people > >would accept /24 and shorter from. > > Not only would this increase the size of the global routing table, but this > would actually decrease reliability for most basement multihomers. Basement > multihomers tend to flap their routes more often than their upstreams. By not > being inside a larger aggregate, these flaps are likely to result in more > significant pockets of unreachability than they would be otherwise. > > DS > >
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