Make&activate-before-break for seamless SDN route updates

Software-Defined Networking (SDN) decouples the control and data planes, enabling limitless possibilities for implementing services and applications on top of the network abstraction layer. The centralized controller provides a real-time view of the entire underlying network infrastructure, and therefore, management of the agile network becomes more simplified. This flexibility requires online routing updates. However, during these updates consistency has to be preserved, i.e., no packet losses or unrecognized duplicates should occur. Moreover, routing updates should be done on the fly in an application-seamless fashion such that no significant irregular delays or “communication hiccups” in packet arrivals are introduced due to the (frequent) updates. In this paper, we are the first to present methods for seamlessly preserving consistency during on-the-fly routing updates. We utilize the make-before-break paradigm, in fact, the make&activate-before-break (MABB) paradigm. We propose two methods for implementing such paradigm. In the first method, the new route is created and activated by duplicating packets along the corresponding portions of both new and old routes, without exceeding bandwidth demands on network links. Only when the controller verifies the correct establishment and operation of the specific portion of the new route, the corresponding portion of the old route is removed. This allows the sender to continue sending packets at an unchanged rate during the entire update process, a rate that is identical to the rate prior and after the update. In the second method, we propose a technique that utilizes the controller for verifying the correctness of the new portion of a route before its activation and the safeness of dismantling the current portion of a route, while keeping the connection operational.