  Associate to each sequence $A$ of integers (intending to represent packet
IDs) a sequence of positive integers of the same length ${\mathcal M}(A)$. The
$i$'th entry of ${\mathcal M}(A)$ is the size (at time $i$) of the smallest
buffer needed to hold out-of-order packets, where space is accounted for
unreceived packets as well. Call two sequences $A$, $B$ {\em equivalent}
(written $A\equiv_{FB} B$) if ${\mathcal M}(A)={\mathcal M}(B)$.
  We prove the following result: any two permutations $A,B$ of the same length
with $SUS(A)$, $SUS(B)\leq 3$ (where SUS is the {\em shuffled-up-sequences}
reordering measure), and such that $A\equiv_{FB} B$ are identical.
  The result (which is no longer valid if we replace the upper bound 3 by 4)
was motivated by RESTORED, a receiver-oriented model of network traffic we have
previously introduced.
