Summary: Instability of FIFO in the Permanent Sessions Model at Arbitrarily
Small Network Loads
Matthew Andrews #
We show that for any r > 0, there is a network of First
InFirstOut servers and a fixed set of sessions such that,
. The network load is r with respect to the Perma
nent Sessions Model with Bounded Arrivals.
. The network can be made unstable.
One of the most important questions that can be
asked about any scheduling algorithm is whether or
not it ensures stability. That is, if the tra#c injected
into the network does not overload any server, do the
queue sizes remain bounded? The reason this can
happen in a network of servers is that if the scheduling
algorithm behaves badly then a server can oscillate
between periods in which it has no data to serve (i.e.
it is starved), and periods in which a lot of data arrives
at the server (thereby causing a queue buildup). For