The locally arbitrary but unique identifier associated with this protocolDir entry. The value for each supported protocol must remain constant at least from one re-initialization of the entity's network management system to the next re-initialization, except that if a protocol is deleted and re-created, it must be re-created with a new value that has not been used since the last re-initialization. The specific value is meaningful only within a given SNMP entity. A protocolDirLocalIndex must not be re-used until the next agent restart in the event that the protocol directory entry is deleted.