  In the paper, a new mechanism for Software-Defined Networking (SDN) flow
aggregation accompanied with multipath transmission is proposed. The
aggregation results in a low number of flow entries in core switches. This type
of scalability improvement of flow processing is obtained thanks to application
of the procedure based on introduction of centrally managed MPLS label
distribution performed by an SDN controller. Moreover, multipath transmission
improves network resource utilization.
  The proposed mechanism does not involve definition of new protocols. It
neither needs application of legacy signalling protocols. Only simple
modifications of the existing solutions, assured by flexibility of OpenFlow,
are necessary. Additionally, the mechanism significantly reduces communication
between the controller and switches, thus enabling a fine-grained flow-level
control. Furthermore, the proposed solution can be incrementally deployed in
legacy networks. The simulations show that a number of flow entries in core
switches can be reduced as much as of 96%, while the overall network traffic is
increased by about 32\%. Moreover, the number of OpenFlow messages is reduced
by about 98%.
