Add some more comments about the MOS score

1 files changed, 22 insertions, 0 deletions

diff --git a/plugins-root/check_icmp.c b/plugins-root/check_icmp.c
index 915710b..12fb7b7 100644
--- a/plugins-root/check_icmp.c
+++ b/plugins-root/check_icmp.c
@@ -1322,7 +1322,27 @@ finish(int sig)
                 }
 
                 if (host->icmp_recv>1) {
+                        /*
+                         * This algorithm is probably pretty much blindly copied from
+                         * locations like this one: https://www.slac.stanford.edu/comp/net/wan-mon/tutorial.html#mos
+                         * It calucates a MOS value (range of 1 to 5, where 1 is bad and 5 really good).
+                         * According to some quick research MOS originates from the Audio/Video transport network area.
+                         * Whether it can and should be computed from ICMP data, I can not say.
+                         *
+                         * Anyway the basic idea is to map a value "R" with a range of 0-100 to the MOS value
+                         *
+                         * MOS stands likely for Mean Opinion Score ( https://en.wikipedia.org/wiki/Mean_Opinion_Score )
+                         *
+                         * More links:
+                         * - https://confluence.slac.stanford.edu/display/IEPM/MOS
+                         */
                         host->jitter=(host->jitter / (host->icmp_recv - 1)/1000);
+
+                        /*
+                         * Take the average round trip latency (in milliseconds), add
+                         * round trip jitter, but double the impact to latency
+                         * then add 10 for protocol latencies (in milliseconds).
+                         */
                         host->EffectiveLatency = (rta/1000) + host->jitter * 2 + 10;
 
                         if (host->EffectiveLatency < 160) {
@@ -1331,6 +1351,8 @@ finish(int sig)
                            R = 93.2 - ((host->EffectiveLatency - 120) / 10);
                         }
 
+                        // Now, let us deduct 2.5 R values per percentage of packet loss (i.e. a
+                        // loss of 5% will be entered as 5).
                         R = R - (pl * 2.5);
 
                         if (R < 0) {