IEEE8021PbbServiceIdentifier
The service instance identifier is used at the Customer Backbone Port of a PBB to distinguish a service instance (Local-SID). If the Local-SID field is supported, it is used to perform a bidirectional 1:1 mapping between the Backbone I-SID and the Local-SID. If the Local-SID field is not supported, the Local-SID value is the same as the Backbone I-SID value.