1.1.f [ii] Latency from rfc 1242 http://www.rfc-editor.org/rfc/rfc1242.txt 3.8 Latency Definition: For store and forward devices: The time interval starting when the last bit of the input frame reaches the input port and ending when the first bit of the output frame is seen on the output port. For bit forwarding devices: The time interval starting when the end of the first bit of the input frame reaches the input port and ending when the start of the first bit of the output frame is seen on the output port. Discussion: Variability of latency can be a problem. Some protocols are timing dependent (e.g., LAT and IPX). Future applications are likely to be sensitive to Benchmarking Methodology Working Group [Page 5] RFC 1242 Benchmarking Terminology July 1991 network latency. Increased device delay can reduce the useful diameter of net. It is desired to eliminate the effect of the data rate on the latency measurement. This measurement should only reflect the actual within device latency. Measurements should be taken for a spectrum of frame sizes without changing the device setup. Ideally, the measurements for all devices would be from the first actual bit of the frame after the preamble. Theoretically a vendor could design a device that normally would be considered a store and forward device, a bridge for example, that begins transmitting a frame before it is fully received. This type of device is known as a "cut through" device. The assumption is that the device would somehow invalidate the partially transmitted frame if in receiving the remainder of the input frame, something came up that the frame or this specific forwarding of it was in error. For example, a bad checksum. In this case, the device would still be considered a store and forward device and the latency would still be from last bit in to first bit out, even though the value would be negative. The intent is to treat the device as a unit without regard to the internal structure.