  Consider a modified, stable, two node Jackson network where server 2 helps
server 1 when server 2 is idle. The probability of a large deviation of the
number of customers at node one can be calculated using the flat boundary
theory of Schwartz and Weiss [Large Deviations Performance Analysis (1994),
  Chapman and Hall, New York]. Surprisingly, however, these calculations show
that the proportion of time spent on the boundary, where server 2 is idle, may
be zero. This is in sharp contrast to the unmodified Jackson network which
spends a nonzero proportion of time on this boundary.
