Latency and Loss - SmokePing
What is SmokePing?
SmokePing is a latency measurement tool. It sends test packets out to the net and measures the amount of time they need to travel from one place to the other and back. For every round of measurement smokeping sends several packets. It then sorts the different round trip times and selects the median, (ie. the middle one). This means when there are 10 time values, value number 5 is selected and drawn. The other values are drawn as successively lighter shades of gray in the background (smoke). Sometimes a test packet is sent out but never returns. This is called packet-loss. The color of the median line changes according to the number of packets lost. All this information together gives an indication of network health. For example, packet loss is something which should not happen at all. It can mean that a device in the middle of the link is overloaded or a router configuration somewhere is wrong. Heavy fluctuation of the RTT (round trip time) values also indicate that the network is overloaded. This shows on the graph as smoke; the more smoke, the more fluctuation.
How does NCREN use SmokePing?
We use SmokePing to measure latency and jitter from a single point on our backbone to multiple points on the network, typically from the main POP in RTP to the Regional POPs, as well as to the point of connection for each connected institution, and a few other key points of interest. These latency measurements are performed by actively injecting traffic into the network, measuring responses and storing the results. Measurements are typically performed at five-minute intervals, and a year's worth of results are retained for future comparison. This provides a relative indication of the quality of the network connection in terms of responsiveness and availability, as well as variation over time of these characteristics. Changes in these measurements can be influenced by a number of factors and may be an indication of some problem or network event.
Typical graph for a low latency connection:
Graph showing some loss, jitter: