A system, method and computer program for ensuring a safe and efficient transmission of a datagram between two isolated points, the datagram being transmitted by a chain of couriers. Limited range communication means are used to pass the datagram from a courier to another, said limited range communication means being based on either a wired or wireless communication equipment. To take the best advantage of the plurality of routes available between two points, a plurality of instances of a same datagram are created. A given credit for the creation of instances is assigned to each datagram, once created. A datagram instance split operation is performed each time two couriers are within range. When a datagram instance is divided into several datagram instances, each datagram instance receives a portion of the credit of the original datagram instance and the total number of credits remains unchanged.