A Mobile Code Bundle Extension for Application-defined Routing in Delay and Disruption Tolerant Networking Carlos Borrego a,* , Sergi Robles a , Angela Fabregues a , Adria S´ anchez-Carmona a a Departament d’Enginyeria de la Informaci´ o i de les Comunicacions Universitat Aut` onoma de Barcelona Barcelona, Spain Abstract In this paper, we introduce software code to improve Delay and Disruption Tolerant Networking (DTN) performance. DTN is extremely useful when source and destination nodes are intermittently connected. DTN implementations use application-specific routing algorithms to overcome those limitations. However, current implementations do not support the concurrent execution of several routing algorithms. In this paper, we contribute to this issue providing a solution that consists on extending the messages being communicated by incorporating software code for forwarding, lifetime control and prioritisation purposes. Our proposal stems from the idea of moving the routing algorithms from the host to the message. This solution is compatible with Bundle Protocol (BP) and facilitates the deployment of applications with new routing needs. A real case study based on an emergency scenario is presented to provide details of a real implementation. Several simulations are presented to prove the feasibility and usability of the system and to analyse its performance in comparison to state-of-the-art approaches. Keywords: Active-DTN, aDTN, networking, DTN, routing, Bundle Protocol, Metadata Extension Block, mobile-code, disaster recovery 1. Introduction Portable devices such as mobile phones or tablets are widely used in daily life. They are generally equipped with wireless-enabled communication, GPS receivers and/or touch screens. The existence of these devices has improved outdoor applications in a great variety of situations. Par- ticularly, they can directly connect with each other. The most popular network configurations for this kind of con- nections are Ad hoc and Mobile Ad hoc (MANET) [4]. This kind of configurations does not require other infras- tructure than the connected devices themselves. New com- munication paradigms are emerging to fill the void for some specific settings not covered by Ad hoc and MANET. This is the case of Delay and Disruption Tolerant Network- ing (DTN) RFC 4838 [15]. DTN implementations are extremely useful when no concomitant network links connect the source and the des- tination nodes at transmission time. This is typical in emergency and disaster recovery scenarios where the con- ventional network infrastructure collapses. It is also com- mon in the space and in undeveloped areas where no con- ventional network is available. Ad hoc communications * Corresponding author Email addresses: cborrego@deic.uab.cat (Carlos Borrego), sergi.robles@uab.cat (Sergi Robles), fabregues@deic.uab.cat (Angela Fabregues), adria.sanchez@deic.uab.cat (Adria S´anchez-Carmona) are defined when nodes keep connected solely during mes- sage transmission. This is also the case of MANET. The capability of DTN to work with intermittently connected nodes makes it suitable for scenarios like the previously described. The lack of infrastructure requirements makes DTN applicable to restoring network connectivity even co- existing with other networking solutions. DTN approaches provide a cheap, easy and ready-to-use deployment. DTN has strong foundations such as the Bundle Proto- col (BP), RFC 5050 [46]. Many groups have been working on their formalities for several years [22, 38]. Moreover, NASA is using DTN in the International Space Station [16]. However, there are still a number of issues to be solved being routing one of the most problematic. We consider routing as the process of selecting which messages are to be transmitted (prioritisation and lifetime control) and where to (forwarding). These issues need innovative solutions that have not been normally used on the Inter- net. The rationale for this is that applications running on such poorly connected networks require different rout- ing algorithms for their specific problems. In contrast to what happens on the Internet, no general purpose routing algorithms exist which satisfy the requirements of all appli- cations at once. One of the design principles of the Delay- Tolerant Networking Architecture, as defined in [15], is to: “Provide coarse-grained classes of service, deliv- ery options, and a way to express the useful life- July 26, 2016