A.PDH物理接口B.同步設備定時源C.復用段保護功能D.高階通道終端功能
A.IP業(yè)務B.窄帶業(yè)務C.ATM業(yè)務D.寬帶業(yè)務
A.IP over PDHB.IP over SDHC.IP over ATMD.IP over WDM