This object sets a rate-limiting threshold, in PDUs, for a tunneled protocol on a given UNI port; once the arrival rate of that protocol's PDUs exceeds this value, the switch starts dropping the excess rather than tunneling them all. Administrators configure this to protect the switch and provider network from a customer site flooding it with an excessive number of STP, GVRP, or other tunneled frames. For example, setting this to 100 would cause the switch to start discarding tunneled PDUs for that protocol once more than 100 per interval arrive, while leaving it at the default 0 means no such limit is applied.