The relative ordering of the MAC/Network adddress pair. There is a global value that starts at 1 and increases by one for each observation of an address pair. When the maximum value of 65535 is reached, the next value will be 1. The global value is used to update this object each time the MAC/Network address pair is observed (and when the entry is initially created). Since the global value starts over again after it reaches its maximum value, there may be more than one entry that has the same value.