Complex sentence: There are multiple ECT algorithms defined for SPB; however, for the future, additional algorithms may be defined; similarly the SPB Adjacency Opaque Equal Cost Tree Algorithm TLV also occurs within the Multi-Topology Intermediate System TLV or the Extended IS Reachability TLV.
Split into simpler sentences: There are multiple ECT algorithms defined for SPB; however, for the future, additional algorithms may be defined. The SPB Adjacency Opaque ECT-ALGORITHM (SPB-A-OALG sub-TLV) occurs within the Multi-Topology Intermediate System TLV or the Extended IS Reachability TLV.