The Severely Errored Seconds (SES) metric is very similar to the regular Errored Seconds (ES). A severely errored second occurs when the ratio of threshold violations during a one-second interval exceeds a certain predefined threshold, which should be higher than the ES threshold.
An SES should always be more severe than a regular ES; ITU-T Recommendation Y.1563, however, mentions only packet loss in connection with SES, and suggests a SES threshold of 50% for this metric. Netrounds has its own user-configurable SES thresholds for packet loss, delay and jitter. SES statistics appear in the table view in the result report.