On Mon, 8 Oct 2007 16:06:52 -0700 David Conrad <drc@virtualized.org> 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