| 摘要 |
<p>PROBLEM TO BE SOLVED: To evade the transfer of an OAM(operation, administration and maintenance) cell up to a normal terminal by transferring a returned OAM cell of 2nd kind selectively to a leaf-side line to which its OAM cell of 1st kind is transferred. SOLUTION: For example, a fault occurs on a line 204. At this point, an exchange 13 sends an AIS(alarm indication signal) cell out to a line 203. This AIS cell is transferred to a user terminal 51 through an exchange 12, a line 202, an exchange 11, and a line 201. A terminal 51 once receiving this AIS cell sends an RDI cell back in the opposite direction this time. This RDI cell is transferred to the exchange 13 through a line 101, the exchange 11, a line 102, the exchange 12, and a line 103. The exchange 13 sends this RDI cell out to only the other line 104 which constitutes a bidirectional line with the faulty line 204. Therefore, the RDI cell is transferred to user terminals 52 and 53 through an exchange 14 and lines 205 and 206, but never transferred to a user terminal 54 where a normal channel is secured.</p> |
