In carrier-grade packet transport networks, service operation, administration and maintenance (OAM) tools are necessary for Carrier Ethernet (CE) service assurance and for measuring compliance with a Service Level Specification (SLS). Frame Loss Ratio (FLR) is one of the most important performance metrics in the Ethernet Virtual Connection (EVC) SLS service attribute specified in MEF 10.4 [1]. FLR is measured using one of two Ethernet loss measurement tools specified in ITU-T Y.1731 [2] and following requirements specified in MEF 35.1 [3]. These two standards are used in the service OAM performance monitoring phase of the MEF 3.0 CE service lifecycle. The Ethernet Synthetic Loss Measurement (ETH-SLM) tool has been used for more than a decade. It has the widest application scope and has been the tool available from most vendors. However, new transport services, such as those that support 5G networks or cloud interconnectivity services, require more accurate and faster FLR measurement capabilities. This need has led to a revival of interest in the original FLR measurement tool, the Ethernet Loss Measurement (ETH-LM) tool, made possible by the availability of the necessary hardware functions. ETH-LM had many restrictions when it was first defined and was not commonly implemented by vendors. This white paper explores the critical role that the ETH-LM and ETH-SLM tools will play in next-generation transport networks that offer CE services. It explains how ETH-LM works and provides a comparison between ETH-LM and ETH-SLM, specifically in terms of FLR accuracy and measurement time. Finally, it points out several additional considerations and conditions for using ETH-LM.