 This paper studies the robustness, effectiveness and efficiency of content-based federated search in hierarchical <i>peer to peer</i> networks when directory services fail unexpectedly. Several recovery methods are studied using simulations with varying failure rates. Experimental results show that quality of service and efficiency degrade gracefully as the number of directory service failures increases. Furthermore, they show that content-based search mechanisms are more resilient to failures than the match-based search techniques.
