The operational mode of the Spanning Tree Protocol. A value of stpCompatibility (0) indicates that the Spanning Tree Protocol operates in IEEE 802.1d mode on all ports. A value of rstpOperation (2) indicates that the Spanning Tree Protocol operates in IEEE 802.1w mode on all ports, except for the ports to which bridges are connected. The ports to which bridges are connected operate in IEEE 802.1d mode for backward compatibility. A value of mstpOperation (3) indicates that the Spanning Tree Protocol operates in IEEE 802.1s mode on all ports, except for the ports to which bridges are connected. The ports to which bridges are connected operate in IEEE 802.1d mode for backward compatibility. This option is available only if object 'hpicfBridgeRstpProtocolVersion' is set to 'ieee8021s'.