Modifying backbone service instance identifiers based on an identified flow of associated frames

In one embodiment, backbone service instance identifiers (I-SIDs) of backbone frames are modified based on flow identification of frames encapsulated therein to induce entropy into the headers of the backbone frames. Backbone packet switching devices use the modified service instance identifier to load balance the corresponding frame through the backbone network. At an exit point of the backbone network, the original backbone service instance identifier (I-SID) associated with a frame encapsulated in a backbone frame is recovered from the modified service instance identifier, with this recovery typically including determining the flow identification of the frame encapsulated in the backbone frame.