Mobile ad hoc networks are characterized by multi-hop wireless links, absen
ce of any cellular infrastructure, and frequent host mobility. Design of ef
ficient routing protocols in such networks is a challenging issue. A class
of routing protocols called on-demand protocols has recently found attentio
n because of their low routing overhead. The on-demand protocols depend on
query floods to discover routes whenever a new route is needed. Such floods
take up a substantial portion of network bandwidth. We focus on a particul
ar on-demand protocol, called Dynamic Source Routing, and show how intellig
ent use of multipath techniques can reduce the frequency of query floods. W
e develop an analytic modeling framework to determine the relative frequenc
y of query floods for various techniques. Our modeling effort shows that wh
ile multipath routing is significantly better than single path routing, the
performance advantage is small beyond a few paths and for long path length
s. It also shows that providing all intermediate nodes in the primary (shor
test) route with alternative paths has a significantly better performance t
han providing only the source with alternate paths. We perform some simulat
ion experiments which validate these findings.