Subject: [rbridge] Must/Should flooding optimization

From: caitlinb at broadcom.com (Caitlin Bestler)
Date: Thu, 23 Mar 2006 14:46:55 -0800

My observation is that those favoring a MUST here are essentially
assuming that if it is only a SHOULD that there will be some 
RBridge vendors who will evaluate the SHOULD language and decide
that their saving 10 cents per port is a valid reason to skip
flooding the rest of the campus.

That is they are not trusted to be proper stewards of the network
when making this design tradeoff. While cynical, it may not be
an innacurate assesment of inevitable market pressures.

But I believe the real intent of using SHOULD, instead of MUST,
is to protect implementations that have truly legitimate 
reasons to make this tradeoff.

For example, an RBridge that is integrated in a multi-blade
system may know that certain links only carry traffic to/from
the blades (i.e there are no internal RBridges that lead back
to the rest of the campus). As such that equipment designer
is in a position to make a fair and unbiased tradeoff between
the cost of filtering tables and the cost of wasting internal
bandwidth. That is exactly the sort of tradeoff that does not
impact interoperability, and we are supposed to avoid using
MUSTs or MUST NOTs to standardize engineering tradeoffs.