Indicates what type of constraint the switch should apply to packets
caught by the (port, protocol) filter.
portMask(1) - Use the etsysESwitchProtocolAllowedToGoTo mask to
determine where the packets may be forwarded.
vlan(2) - Classify the packets as belonging to the VLAN
etsysESwitchProtocolVlanId.
Note that on the RoamAbout AccessPoint R2, port/protocol constraints
can sometimes take a back seat to other kinds of access controls.