As the networks are becoming increasingly heterogeneous, it is expected that future internetworks will interconnect different types of network including infrastructure-based and ad-hoc wireless networks. Moreover, a number of emerging applications such as environmental monitoring, emergency response, etc., require that future internetworks be tolerant to connectivity disruptions. Interconnecting these heterogeneous networks poses several challenges including seamless message delivery and identification of mobile nodes. This book present 3 major contributions: 1) A classification of existing DTN routing protocols by breaking up existing routing strategies into tunable routing modules. 2) A new message delivery framework called MeDeHa to provide message delivery across heterogeneous networks prone to intermittent connectivity. MeDeHa is able to seamlessly bridge infrastructure-based and ad-hoc networks, through devices carrying multiple interfaces and by the integration of existing protocols. 3) A naming mechanism called HeNNA for heterogeneous networks prone to connectivity disruptions, which provides message delivery to nodes irrespective of their IP addresses.