If a parent doesn't hear from a child for a timeout period, it drops the child from its list of children. (If this action causes its child list to become empty, the parent stops acting as a forwarder altogether.) The only remaining failure point is that of the root node, and Pastry itself automatically overcomes this.
If a parent doesn't receive updates from a child for an extended period, it removes that child from its list of children. (If this action results in an empty list, the parent stops acting as a forwarder.) The sole remaining issue is at the root node, and Pastry automatically resolves this.