VMware Smart Assurance Optical Transport Management Suite has four Domain Managers:
WDM (Wavelength Division Multiplexing) - Monitors WDM optical network elements.
SONET/SDH - Monitors SONET or SDH elements that are faster than 34M such as VC-3 and AU-4 protocols.
PDH - Also known more accurately as Low-order SONET/SDH, this domain monitors SONET or SDH elements that are 6M or slower such as VC-2 and AU-2 protocols.
WDM-NG (Next Gen) works with EMC M&R to collect data from EMS systems that support TMF 864.
Each Domain Manager (except WDM NG) consists of a pair of servers: Topology server and Analysis server. For WDM-NG, the Analysis & Topology servers are combined.
In a typical deployment, there may be multiple IP servers, SONET/SDH servers, WDM servers, and Low-order SONET/SDH (PDH) servers. There may also be multiple adapters. In Figure 2, the XD OTM-IP server appears to import topology from all Domain Managers. But, in larger networks, you may need a separate XD OTM-IP server deployed for IP-to-WDM, IP-to-WDM-NG, IP-to-PDH, and IP-to-SDH analysis.