A router MUST have a mechanism to allow routing software to determine whether a physical interface is available to send packets or not; on multiplexed interfaces where permanent virtual circuits are opened for limited sets of neighbors, the router must also be able to determine whether the virtual circuits are viable. A router SHOULD have a mechanism to allow routing software to judge the quality of a physical interface. A router MUST have a mechanism for informing the routing software when a physical interface becomes available or unavailable to send packets because of administrative action. A router MUST have a mechanism for informing the routing software when it detects a Link level interface has become available or unavailable, for any reason. |