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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Creative routing (was Re: Policy Statement ...)
Well, there's an alternate tactic for a tiny tiny company. MCI Sprint | / The Site-----BBN / \ Alternet ANS 1/ Pick a provider from whom to acquire a tiny amount of aggregatable address space. 2/ Choose a community attribute which you tag on your prefixes. The easiest would probably be "no-export". The ideal would be one meaning "export only to my set of providers". 3/ router bgp X neighbor ProviderX route-map set-community out neighbor ProviderX send-community neighbor ProviderX filter-list 1 out ... ip as-path access-list 1 permit ^$ ip as-path access-list 1 deny .* route-map set-community permit 10 set community <value> 4/ each provider, at each interchange router bgp Y neighbor PeerA route-map policy out neighbor PeerA send-community neighbor PeerB route-map policy out neighbor PeerB send-community ... neighbor AnotherPeer route-map other-policy out ... route-map policy permit X match community <value> set community no-export ... route-map other-policy deny X match community <value> 5/ on ONLY the provider supplying addresses, configure at (or very near) *each* interchange point this: ip route CIDR-SUPERBLOCK MASK null0 router bgp M network CIDR-SUPERBLOCK mask MASK It's important that the route for CIDR-SUPERBLOCK never fully vanish, or you lose connectivity to your non-providers. Hence the provider you choose address-space from should have a good record of knowing what it's doing and always having at least one path by which to announce the CIDR-SUPERBLOCK to the world. That's about the only big qualification. There. Now you have fully redundant connectivity among all your providers. Your address space is aggregated everywhere except in your set of providers. Each of your providers will carry at least two prefixes: the CIDR superblock and the much longer end-site prefix. Each provider advertises reachability for your prefix to each of your other providers; however, the rest of the world sees only the CIDR-SUPERBLOCK. If a packet hits the router announcing the superblock and that router has no route to the long prefix, it probably will be hearing the more-specific announcements from at least one of your other peers, and will hand traffic to them. You can even play games with AS-path lengths on the more-specific prefix in order to select which provider will handle the bulk of traffic from the set of people at interexchange points who are not your providers and therefore not receiving the most-specific prefix. And all sorts of other nifty hacks. I bet it's even fairly easy for most providers to attach a cost on all the activities needed to support this, so you could end up proving Yakov's thoughts about the Push operation. It won't be cheap. This is very-brain-and-slightly-CPU-intensive. Dear small company needing a /28 and comparing itself to Netscape: please forward my standard consulting fee (a pound of good European chocolate) to my office address when you have a moment. Sean. |