Enabling SCADA cluster and cloud for smart grid using hierarchical multicast; the PTMF framework

The increasing number of new devices and RTUs connecting to smart grid is complicating the scalability of entire control systems as they are more overloaded due to the number of connections, and even more, by the complex synchronization mechanism used between principal and emergency multisite systems. On this paper, we present how multicast protocols could be used on telecontrol front-ends of SCADA systems to reduce the number of connections, load and bandwidth, improving efficiency and reducing network costs. Applying multicast will provide the use of complete functional and operative distributed SCADA clusters along the enterprise, easily full multisite, plug and play, to be used on an active-active form by distributed control centers. Options to use a private cloud in an enterprise are presented too. Finally, we present PTMF, a hierarchical reliable multicast protocol and framework to be used in both environments one-to-many (1:N) as well as many-to-many (N:N). PTMF gets great scalability by organizing the members participating on hierarchical local groups. PTMF uses a hybrid reliable control technique, based on receiver and on sender, with an error control distributed among all members of each local group. The protocol can operate in four modes: Reliable, Late Reliable (it allows new members to join to the current connection), Unreliable and Sorted Unreliable. PTMF uses both multicast and unicast retransmissions, it has flow control and congestion avoidance features; it incorporates cypher and authentication of packets and allows control of bandwidth consumed by each multicast sender.