On Tue, 03 Sep 2002 19:51:23 -0700, David Conrad <david.conrad@nominum.com> said: > On 9/1/02 7:30 AM, "Simon Leinen" <simon@limmat.switch.ch> wrote: >>>> - one prefix for each ISP in the world >>>> - one prefix for each POP or campus in your network >>>> - one prefix for each LAN in your POP or Campus >>>> - additional prefixes that you decide to carry for your own reasons (eg, >>>> policy) >>> My, that's a lot of prefixes. I'm sure I'm missing something here. >> Probably - note how the scope gets narrower as you go down to smaller >> parts of the Internet. > Well, yeah, but if you want to gain full benefit of multi-homing, > each of these prefixes would need global visibility, no? If you want to enjoy the FULL benefits of multi-homing, all the other folks you want to community with must be multi-homed too, so that there are no single points of failure :-) Probably the typical site could achieve 95% of the benefits of multihoming with an impact on only 5% of the global Internet. What is needed is some sort of feedback loop that weighs the interest of multi-homing entities against its impact on remote parts of the infrastructure. In the spirit of "think globally, act locally", here's what we do as a regional ISP: We have relatively strict inbound route filters based on RIR assignment policy and traditional defaults for swamp space (/24 or shorter in 192.0.0.0/7, /19 or shorter in the non-RIR-administered part of 0.0.0.0/2 and 128.0.0.0/3 etc.). In our neck of the woods, most ISPs send e-mails to their peers when they want to start announcing new paths. When I notice that the of the new prefixes violate our prefix filters, I respond that we won't be accepting those routes by default, but would agree to add an exception to the filters for a limited amount of time if the new customer will renumber into a larger aggregate. This at least creates a small incentive for ISPs to think about RFC2260-like solutions for multihoming customers, or for customers who (are forced to) change ISPs to renumber into their new ISP's space. A caveat is that we have partial routing, carrying mostly only European routes, so we don't drop traffic to networks whose routes we filter. -- Simon.