Contact Graph Routing ( CGR ) is a dynamic routing system that computes routes through a time - varying topology composed of scheduled , bounded communication contacts in a network built on the Delay - Tolerant Networking ( DTN ) architecture . It is designed to support operations in a space network based on DTN , but it also could be used in terrestrial applications where operation according to a predefined schedule is preferable to opportunistic communication , as in a low - power sensor network . This paper will describe the operation of the CGR system and explain how it can enable data delivery over scheduled transmission opportunities , fully utilizing the available transmission capacity , without knowing the current state of any bundle protocol node ( other than the local node itself ) and without exhausting processing resources at any bundle router .