topological closeness....

one other solution (being implemented, I believe), is a DNS server
that listens to the BGP traffic, so it knows how far away things are,
and when you ask it, it can chose from multiple responses to pick
one "close".


The only problem that it does not work at all.

Which WWW server is closer to me - one with BGP path

  1239 3491 690 1333 (

or one at

  1239 1792 (

The second is in China, for God's sake!

There ain't no such thing as global metrics. The only
useful kind of metrics is administrative, and therefore
they cannot reflect any real characteristics of paths.

Even if there are uniform metrics, how do you tell
which link is overloaded and which isn't?

Cacheing appears to be the only sane way to distribute
load. You always know where the closest cacheing server is.
Now, there's a problem with coherency, but at least it
can be done w/o magic.


check out sonar, draft-moore-sonar-01.txt.