Loop prevention

SPBM nodes collect topology data independently to calculate forwarding paths. Transient loops might occur during SPT recalculation caused by a network flapping because the latency varies for an LSP to reach the SPBM nodes. To prevent transient loops, SPBM uses the Agreement Protocol (AP) to exchange LSDB synchronization status. After a topology recalculation, ISIS-SPB issues new forwarding entries to the data plane only if topology data is synchronized between the SPBM node and its adjacent neighbors.

	NOTE: In this document, "AP" refers to agreement protocol. In other documents, "AP" can also refer to access points.