Traffic Trend shows graphically the long-term utilisation trends of the watch, both average and 95th percentile values.
Two trends are shown on the chart:
95th percentile level shown as a green bar. 95th percentile is a commonly-accepted normal maximum level which shows the peak load on the link, after removing the busiest 5% of samples.
Average traffic level on the circuit, shown as a blue bar overlaid on the green bar
The trend chart uses the date and time period selected in the time bar at the top of the page and shows the previous 24 periods of the same length (day, week or month). So if you select Month and January 2017, the trend chart will start at January 2017 and show the previous 24 months (if Highlight has that much history for this watch).
In a number of places Highlight reports the 95th Percentile value for a measurement. What does this mean?
Highlight checks traffic levels on circuits (for example Broadband links, Ethernet, WAN Circuits) every three minutes. Each sample produces amongst other things a utilisation metric such as 10% busy, 55% busy, 96% busy, etc.
It's very useful to know the peak or maximum level that a line reaches, because it helps see when it's getting too full, needs upgrading, or might be causing slow response times. The problem is that most lines get very busy on occasion - downloading a large file, for example - and it would be overreacting to upgrade or adjust things just because of these very occasional bursts of traffic. That would be like widening a motorway just because it's congested for half an hour every Monday morning.
An industry-standard approach to this is to ignore the busiest five percent of checks and take the highest remaining value. In theory, this ignores those occasional peaks, and gives you a realistic maximum or frequently hit maximum for the line. The number of the percentile shows you how many samples have been ignored. For a 95th percentile, it's the busiest 5% (say, 50 samples from 1000). Some people use an 80th percentile, in which case you ignore the busiest 20% of samples (200 samples from 1000).
In summary, 95th% means the ninety-fifth percentile value for the line, which in turn means the busiest that the line gets in normal usage, excluding those occasional peaks which might distort things. Percentiles are often used as the basis for usage-based billing.