We give complete characterizations for the classes of graphs with uniform c
ost links that admit optimum all shortest paths 1-SLIRS (strict linear inte
rval routing schemes) and 1-LIRS (linear interval routing schemes). The cha
racterization of all the interval routing schemes with uniform cost links t
hat represent only a single shortest path is known to be NP-complete, For a
ny integer k > 0, we also show that the class of graphs with dynamic cost l
inks that admit optimum all shortest paths L-IRS (SIRS, LIRS, SLIRS) is equ
ivalent to the class of graphs with dynamic cost links that admit an optimu
m single shortest path l-IRS (SIRS, LIRS, SLIRS) and also equivalent to the
class of graphs with dynamic cost links that admit single paths up to any
constant stretch factor k-IRS (SIRS, LIRS, SLIRS). (C) 2001 John Wiley & So
ns, Inc.