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    Ethernet Synthetic Loss Measurement Overview

    Ethernet synthetic loss measurement (ETH-SLM) is an application that enables the calculation of frame loss by using synthetic frames instead of data traffic. This mechanism can be considered as a statistical sample to approximate the frame loss ratio of data traffic. Each maintenance association end point (MEP) performs frame loss measurements, which contribute to unavailable time.

    A near-end frame loss specifies frame loss associated with ingress data frames and a far-end frame loss specifies frame loss associated with egress data frames. Both near-end and far-end frame loss measurements contribute to near-end severely errored seconds and far-end severely errored seconds that are used in combination to determine unavailable time. ETH-SLM is performed using synthetic loss message (SLM) and synthetic loss reply (SLR) frames. ETH-SLM facilitates each MEP to perform near-end and far-end synthetic frame loss measurements by using synthetic frames because a bidirectional service is defined as unavailable if either of the two directions is determined to be unavailable.

    There are the two types of frame loss measurement, defined by the ITU-T Y.1731 standards, ETH-LM and ETH-SLM. Junos OS supports only single-ended ETH-SLM. In single-ended ETH-SLM, each MEP sends frames with the ETH-SLM request information to its peer MEP and receives frames with ETH-SLM reply information from its peer MEP to perform synthetic loss measurements. Single-ended ETH-SLM is used for proactive or on-demand OAM to perform synthetic loss measurements applicable to point-to-point Ethernet connection. This method allows a MEP to initiate and report far-end and near-end loss measurements associated with a pair of MEPs that are part of the same maintenance entity group (MEG).

    Single-ended ETH-SLM is used to perform on-demand or proactive tests by initiating a finite amount of ETH-SLM frames to one or multiple MEP peers and receiving the ETH-SLM reply from the peers. The ETH-SLM frames contain the ETH-SLM information that is used to measure and report both near-end and far-end synthetic loss measurements. Service-level agreement (SLA) measurement is the process of monitoring the bandwidth, delay, delay variation (jitter), continuity, and availability of a service. It enables you to identify network problems before customers are impacted by network defects. In proactive mode, SLA measurements are triggered by an iterator application. An iterator is designed to periodically transmit SLA measurement packets in the form of ITU-Y.1731-compliant frames for synthetic frame loss measurement . This mode differs from on-demand SLA measurement, which is user initiated. In on-demand mode, the measurements are triggered by the user through the CLI. When the user triggers the ETH-SLM through the CLI, the SLM request that is generated is as per the frame formats specified by the ITU-T Y.1731 standard.

    Modified: 2016-01-28