is transferred between the cn 102 and 104 and the mma 39 s mmn 108 at 190 during the time period when the cn is transferring packets a reachability test 110 is conducted at 200 between the ar 106 and the mmn 108 at 202 the ar triggers an unreachability detection procedure it should be noted that the mmn has switched off its interface prior to flooding the network which triggers the unreachability detection by the ar the unreachability detection procedure shows the ar that the mmn is unreachable on the link the ar 106 then waits for a predefined time period at 206 upon expiration of the predefined time period the ar sends a bfr message 112 to each cn 39 s address stored in its cache at 208 preferably all bfr messages are authenticated with kc during the waiting time period the ar may store the received data packets in its cache memory since the mmn may just be out of reach because of other possible factors for example noise on the link and the like upon receiving the bfr message 208 the cns 102 and or 104 determine whether the coa carried in the message is already stored in the cn 39 s bce 120 at 210 the cn.