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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: all the mails on Filtering
On Wed, 2002-11-13 at 13:25, Harsha Narayan wrote: > So what happens to multihoming assignments made by the ISP? That means > the multihoming assignment can't be used as a backup. If the customer's This has been rehashed time and time again on this list, and others. The fact is, ISPs have to filter somewhere to keep routing table growth in check. It makes more sense to filter out announcements longer than the longest assignment within an RIR's space than to filter on any arbitrary boundary. I think everyone will agree with that, even if they do not agree that filtering is necessary or good. As an example of why filtering is good, click on this link and visit the CIDR Report AS Summary for an ISP here in Kentucky. They used to have over 50 useless announcements within one /18, for which they had an aggregate announced as well. They seem to have gone to some efforts to reduce the route table pollution the emit, and I applaud their efforts, however you can further reduce the amount of pollution you accept from them, and other ISPs who mistakenly announce from their IGP or for any other reason do not announce blocks as they are assigned by the RIR, simply by filtering on the minimum assignment size. http://bgp.potaroo.net/cgi-bin/as-report?as=11979&view=4637 I think there are very few networks who purposely announce longer networks to control their inbound traffic flow, verses the number who mistakenly do so. Again, everyone will agree. Except, perhaps, Ralph Doncaster. And if you want to spend your FIB entries, and your money, making your bits flow to him in the manner that's most cost-effective for ISTOP, then more power to you. Most folks will agree that is up to Ralph and Ralph's ISP(s) to work out, though. -- Jeff S Wheeler <[email protected]>
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