Iljitsch van Beijnum wrote:
On Fri, 28 Sep 2001, Sean M. Doran wrote:
let me say that not only am I a strong supporter of filtering, I have also suggested fairly seriously to some registry-types that it is fair to allocate individual /32s as necessary to contain address consumption.
So how is this supposed to work? For instance, I get a /27 and an AS number, and I want to multihome. But nobody will listen to my announcements. This is not a workable solution.
Hello; I actually have some information on this - look at http://www.multicasttech.com/status/cidr.html and http://www.multicasttech.com/status/histogram.cidr.bgp Of the announcements we receive (we are multihomed to 3 ISP's, but not to Verio), 57.6 % of the prefixes are /24's, and about 1/2 of these are holes in another address block. Presumably, the other 1/2 are mostly /24's from the swamp. So, a Verio like filtering policy would filter out about 1/2 of the /24's (a little more, actually) and leave the rest. This seems somewhat arbitrary to me. By contrast, only ~ 0.1% of the announcements are /25's or longer. SO, in the spirit of setting the speed limit at the speed people actually drive, I would suggest that a reasonable solution would be to admit up to /24's. I know that this will not be an entirely popular opinion. -- Regards Marshall Eubanks
It is possible to take the position that the responsibility of the ISPs to filter and the responsibility of the RIRs to assign are completely unrelated, but that only holds in theory. In practice, people want to get addresses they can use and use the addresses they can get. So there should be a reasonable overlap.
Multihomers generally announce just a single route and there are less than 25k AS numbers so the majority of routes is NOT from multihomers so it seems somewhat harsh to effectively forbid multihoming.
But while we're all discussing drafts on multi6, the routing table is still growing so some filtering should be expected. Is there really no way we can all agree on a filtering policy that keeps the routing table in check but still leaves some room for responsible multihoming?
For instance: each AS gets to announce either a single route (regardless of prefix size) or only RIR-allocation-sized blocks.
(The problem with this is that you can't make a reasonably sized filter that enforces this policy, so you would have to trust your peers to some degree.)
That is, the registries are correctly focusing on that resource-management, and should spend energies on reclaiming wasted space (hello MIT!) rather than on managing multiple scarce resources.
IP address space is only a scarce resource because it is allocated in huge chunks. If we would be able to re-allocate individual un-used IP addresses, we wouldn't run out for a _very_ long time.
Iljitsch van Beijnum
T.M. Eubanks Multicast Technologies, Inc 10301 Democracy Lane, Suite 410 Fairfax, Virginia 22030 Phone : 703-293-9624 Fax : 703-293-9609 e-mail : tme@multicasttech.com http://www.on-the-i.com Test your network for multicast : http://www.multicasttech.com/mt/ Check the status of multicast in real time : http://www.multicasttech.com/status/index.html