The point being that if you have an arbitrary bunch of firewalls and
NATs between any two points, then you are forced into telephone-like
"call set-up" scenarios, which don't really scale to large groups,
specially when the application consists of sporadic messages to
arbitrary destinations.
or in general, that networked applications sometimes involve more
than two parties that are mutually communicating (and they don't
necessarily use TCP exclusively) a lot of the proferred solutions
seem to assume that pairwise mappings are sufficient; they aren't.
Keith