1. A non-transitory computer-readable storage medium having stored contents that configure a computing system to perform a method, the method comprising: obtaining information regarding a first virtual computer network having multiple computing nodes, the first virtual computer network being overlaid on a distinct substrate network that interconnects the multiple computing nodes; and automatically managing one or more communications sent by one or more of the multiple computing nodes of the first virtual computer network, the multiple communications each being sent by a sending one of the multiple computing nodes and having an intended final destination, the managing of each of the one or more communications being performed by the configured computing system and including: automatically determining one or more alternative paths from the sending computing node for the communication to the intended final destination of the communication; automatically determining a first quantity of one or more parts into which to encode the communication based at least in part on information about the determined alternative paths, and encoding the communication into the determined first quantity of parts; and forwarding each of the parts of the communication from the sending computing node for the communication to the intended final destination of the communication along one of the determined alternative paths, wherein each of the determined alternative paths is used to forward at least one of the parts.