FabricIndex: Branded<number, "FabricIndex">

Each fabric supported on a node is referenced by fabric-index that is unique on the node. This fabric-index enables the look-up of the full fabric information from the fabric-index. A fabric-index of 0 (zero) or null SHALL indicate that there is no fabric associated with the context in which the fabric-index is being used. If fabric-index is used in a context that is exclusively associated with a fabric, such as fabric-scoped data model elements, then the fabric-index values SHALL NOT include 0 (zero) or null.

MatterSpecification.v10.Core ยง 7.5.2