data communication resources expressed in bits/second or multiples of it (kilobits/s, megabits/s, etc.) Frame transfer delay (FTD): Also known as latency, this is a measurement of the time delay between the transmission and the reception of a frame. Typically this is a round-trip measurement, meaning that the calculation measures both the near-end to far-end and far-end to near-end direction simultaneously. Frame delay variations (FDV): Also known as packet jitter, this is a measurement of the variations in the time delay between packet deliveries. As packets travel through a network to their destination, they are often queued and sent in bursts to the next hop. There may be prioritization at random moments also resulting in packets being sent at random rates. Packets are therefore received at irregular intervals. The direct consequence of this jitter is stress on the receiving buffers of the end nodes where buffers can be overused or underused when there are large wings of jitter. Frame loss ratio (FLR): Typically expressed as a ratio, this is a measurement of the number of packets lost over the total number of packets sent. Frame loss can be due to a number of issues such as network congestion or errors during transmissions. Frame loss ratio with reference to the SAC: Typically expressed as a Pass / Fail indication. SAC (Service Acceptance Criteria) is the part of the network operators SLA which references the FLR requirement for the network path under test. Availability (AVAIL): Typically expressed as a % of up time for link under test for example does the network pass the 5 "9's" 99.999% up time. See also Ethernet Private Line References The Essentials of Ethernet Service Activation (Multi-Service Y.1564) ITU Y.1564 Ethernet Testing ITU y.1564 test methodology New Ethernet test standards and procedures address changing network traffic Benchmarking Terminology for Network Interconnection Devices Benchmarking Methodology for Network Interconnect Devices ITU specifications External links eSAM - Performance Assessment IxNetwork Y.1564 QuickTest SAMComplete MEF 10.1 MEF 10.2 Ethernet standards ITU-T Y Series Recommendations