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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Upstreams blocking /24s? (was Re: How Not to Multihome)
On Mon, 8 Oct 2007 16:06:52 -0700 David Conrad <[email protected]> wrote: > > Hi, > > On Oct 8, 2007, at 2:48 PM, Scott Weeks wrote: > > However, if it's less than a /24 it won't get very far as most > > > upstreams block prefixes longer than a /24. > > I'm curious: a couple of people have indicated they do not believe > this to be the case. Anybody have any hard data on what filters are > actually in use today? That's a good question. http://www.nanog.org/mtg-0105/prefix.html says what was in use 6.5 years ago; it would be good to look at newer data. > > Others have indicated that such filters (assuming they exist) will > not last in the face of paying customers presenting longer than /24 > prefixes for routing. Specifically, that ISPs will relax their > filters (allowing longer than /24) in order to get their peers to > accept their long prefixes. Anybody have an opinion on the > likelihood of this? > The traditional answer has been "paying whom?" A given ISP's customers might pay it to announce their routes; *maybe* they'll have bilateral agreements with some of their peers to carry each other's longer routes. But what about the next hop? Put another way, there's been a lot of discussion -- pardon me, a *FLEEPING LOT of DISCUSSION* -- on this list lately about how lots of folks need to upgrade line cards and/or IOS and/or routers to keep up with the growth of the routing table. If the growth is due to long prefixes, who pays? Again, it's (relatively) easy to charge your own customers. --Steve Bellovin, http://www.cs.columbia.edu/~smb
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