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Traditionally, ad hoc networks have been viewed as a connected graph over which end-to-end routing paths had to be established.Mobility was considered a necessary evil that invalidates paths and needs to be overcome in an intelligent way to allow for seamless ommunication between nodes.However, it has recently been recognized that mobility an be turned into a useful ally, by making nodes carry data around the network instead of transmitting them. This model of routing departs from the traditional paradigm and requires new theoretical tools to model its performance. A mobility-assisted protocol forwards data only when appropriate relays encounter each other, and thus the time between such encounters, called hitting or meeting time, is of high importance.In this paper, we derive accurate closed form expressions for the expected encounter time between different nodes, under ommonly used mobility models. We also propose a mobility model that can successfully capture some important real-world mobility haracteristics, often ignored in popular mobility models, and alculate hitting times for this model as well. Finally, we integrate this results with a general theoretical framework that can be used to analyze the performance of mobility-assisted routing schemes. We demonstrate that derivative results oncerning the delay of various routing s hemes are very accurate, under all the mobility models examined. Hence, this work helps in better under-standing the performance of various approaches in different settings, and an facilitate the design of new, improved protocols.