[2] Want to tune inbound traffic? Fine... advertise those longer prefixes to your upstreams/peers. But don't make the rest of the Internet suffer. Communities good. Extra routes bad.
but people dont advertise long prefixes in order to simply make use of two providers for the sake of it, they do it in order to
IGP-into-BGP causes this, and is hardly for preferring traffic from one upstream.
create their own unique routing policies which by definition needs to be internet-wide
Tag a single netblock with a community or MED. Don't split it into two longer prefixes. Of course, that might require inter-AS cooperation.
but if only one provider is agg'ing it will always prefer the most specific route regardless of tags
i would envisage all kinds of problems too where the aggregating upstream accepts your specific routes via another isp by mistake and then your transit traffic ends up going all round the place.. you'd be advertising /24s to peers and all but one transit, with primary transit aggregating up to /16 or whatever, feels bad..
Hmmmm. So I have customer X, who also connects to backbone B. They advert several blocks, which I agg to 192.168.0.0/19. B does not agg the blocks... but I'd also agg what I hear from B, into the same /19. No problem here.
no problem for you, but B's other peers wont agg and they will only see B's more specific path as valid
Or perhaps a hack... match ^[0-9]*_ and prefer it over longer prefixes. i.e., if you can get there directly, it's better than going through another AS.
Your point definitely merits thought... but I'm not sure that it's insurmountable.
i see where youre coming from but its not a part of bgp4. you could write it into bgp5, trouble is theres a lot of routes out there less specific and when you turn on this feature it could be very unpredictable. the other issue is you dont really want to prefer any route, you want them equally valid and how can you do that unless all the upstreams apply the same tags/rules theres only 20000 AS's, and its the AS that is defined as having a single routing policy not the prefixes. why cant internet routing be based on AS announcements, yeah i know you need to rewrite everything but i couldnt think of a better idea. :) Steve