This attribute specifies when bumping may be triggered as a result
of this call being routed/rerouted or optimized. There are two
possibilities:
bumpWhenNecessary: means that this call will only trigger the
bumping of another call (subject to setup/holding priority
restrictions) when there is no other way to establish a route for this
call.
bumpToObtainBestRoute: means that this call may trigger the
bumping of other calls (subject to setup/holding priority
restrictions) if doing so would result in this call obtaining a better
(lower cost/delay) route.
Since bumping to obtain the best route can be somewhat intrusive
the default is only to bump when there is no other way to route the
call.