Robert Raszuk wrote:
IGP metric is used as route preference,
And that's the issue. Neither IGP metric nor BGP path attributes today
reflect reality of true network paths.
I'm afraid you are not familiar with BGP policy, where you don't have
to blindly rely on path attributes.
When I look at my BGP table in NY I get path to Europe via Seattle just
because such path has 1 AS less in the AS-PATH and neglect the fact that
there is alternative path just next to it with +1 AS but shorter RTT of 150
ms.
That you configure your BGP poorly does not mean others can't have
better policy to favor the alternative path.
As is written in the draft:
Note that end to end multihoming works with the separation between
inter domain BGP and intra domain routing protocols, if BGP routers,
based on domain policy, assign external routes preference values
(metric) of intra domain routing protocols.
proper IGP metric may be given by proper policy based on such knowledge
(not carried by BGP) as "with +1 AS but shorter RTT of 150ms".
Masataka Ohta
