Message Ferrying is a mobility assisted technique for working around the disconnectedness and sparsity of Mobile ad hoc networks. One of the important questions which arise in this context is to determine the routing of the ferry, so as to minimize the buffers used to store data at the nodes in the network. We introduce a simple model to capture the ferry routing problem. We characterize stable solutions of the system and provide efficient approximation algorithms for the MIN-MAX BUFFER PROBLEM for the case when the nodes are on hierarchically separated metric spaces. © Ammar, Chakrabarty, Das Sarma, Kalyanasundaram, Lipton.