| 释义 |
SDH (Synchronous Digital Hierarchy) In 1988, the CCITT, predecessor to the ITU-T, accepted the SONET standards, with modifications that were mostly at the lower multiplexing levels in order to accommodate the complexities of internetworking the disparate national and regional networks. The ITU-T Recommendations referenced are G.707, G.708, and G.709. See also SONET. |