[rbridge] How to deal with RBridge-Rbridge link metrics ?

[Pierre Francois]

Hi,

I have questions regarding "IS-IS like" link metrics that would be used in
trill.

Shouldn't the requirements specify that if zero configuration must be made
possible, it should also be made possible to configure RBridge->RBridge
link metrics in order to allow smarter than smallest hopcount path
forwarding...

In the zero configuration case, what would be the default metric ?

Also, what would be the behaviour of a RBridge if not all the links have a
configured metric ?

Consider all links have default metrics or configured links have their
configured metrics and the other the default ?

Wouldn't the last solution lead to a forwarding mess during a migration
from an unconfigured link metrics architecture to a configured one ? For
example if the default metric is 1, traffic will be concentrated on
unconfigured links during the transition as they will provide the shortest
paths...

If this solution is used, shouldn't the default metric be made
configurable in order to solve (at least try to solve) this problem ?

Also, if link metric config is possible, shouldn't there be a requirement
stating that a metric re-configuration should not lead to packet
loops/loss ?



Pierre.