IV - high volume UDP messaging engine

My own Q: How do you make UDP reliable?
My own Q: can snoop capture UDP traffic?
Q: Why would multicast use a different address space?
Q: How do you avoid full GC

Q: why would a server refuse connection?
%%A: perhaps tcp queue is full, so application layer won't see anything

Q: what's the impact of 64 bit JVM?
Q: NIO?
Q: how do you communicate with QA the impacts of your changes?
Q: how many package break releases did your team have in a year?
Q: In a live production system, how do you make configuration changes with minimal impact to existing modules?