區(qū)段層 at the section layer: 在段層layer and section: 層和段msl multiplex section layer: 復(fù)用段層oms optical multiplexer section layer: 光復(fù)用段層osn optical section layer stm-nn: 光段層下載手機(jī)詞典可隨時(shí)隨地查詞查翻譯