IGPs in use

Just as with ISIS .. and most anything else. In order to continue operating
when it's "ceiling" is reached, network design and vendor implementation must
be tailored (optimized) to accommodate shortcomings in the specific

I've seen one of these "theoretical" ceilings w/ISIS at a previous employer
(one of the "big 5"). I guess you could say "allowing the glass to break
wasn't an option".