common method to count traffic volume on IX

Hi, many Internet exchange points post publicly available graphs which describe aggregated traffic volumes on IX. For example: Netnod: http://www.netnod.se/ix-stats/sums/ AMS-IX: https://www.ams-ix.net/technical/statistics LINX: https://www.linx.net/pubtools/trafficstats.html Is there a common method to count this traffic on a switch-fabric? Just read all the switch interface "packets input" counters with an interval to get the aggregated input traffic and read all the switch interfaces "packets output" counters to get the aggregated output traffic? regards, Martin