Shared network variables RT FIFO versus buffering

Hello,

can anybody tell me why I should use network shared variables with buffering and RT FIFO (http://www.ni.com/white-paper/4679/en/)?

Only buffering: ok (reader can catch up + I can use fancy none-RT data types).

Only RT FIFO: ok (the high-prio reader/writer is time deterministic).

FIFO and buffering: why? Isn't a FIFO a buffer already?

Thanks!

Peter