NDT-DEV email list created

Revision: 576
Author:   

Date:     Thu Sep  1 06:26:58 2011
Log:      Added description how the following variables are computed:  
Packet loss, Packets arriving out of order, Average round trip time  
(Latency/Jitter)
http://code.google.com/p/ndt/source/detail?r=576

Modified:
 /wiki/NDTTestMethodology.wiki

=======================================
--- /wiki/NDTTestMethodology.wiki       Thu Sep  1 05:51:41 2011
+++ /wiki/NDTTestMethodology.wiki       Thu Sep  1 06:26:58 2011
@@ -223,12 +223,44 @@

 When this variable's value is 1456, then it means that the packet size is  
preserved End-to-End.

-=== Abnormal Conditions Detection ===
-
- * high packet loss
- * packets arriving out of order
-
-=== Latency/Jitter ===
-
- * Multiple measurements of the round trip delay and per-packet  
transmission/arrival times are collected.
- * The delay for each measurement is summed and divided by the total  
number of measurements to generate the average round trip delay.
+== Computed variables ==
+
+=== Packet loss ===
+
+The packet loss proportion is computed using the following formula:
+
+{{{
+CongestionSignals/PktsOut
+}}}
+
+where:
+ * *!CongestionSignals* - The number of multiplicative downward congestion  
window adjustments due to all forms of congestion signals
+ * *!PktsOut* - The total number of segments sent
+
+When the `CongestionSignals` value is *0*, then the packet loss proportion  
is set to the following values:
+ * *0.0000000001* - if a link type detected by the Bottleneck Link  
Detection algorithm using the *Client --> Server data packets*'  
inter-packet arrival times is faster than a 100 Mbps Fast Ethernet subnet.
+ * *0.000001* - otherwise
+
+=== Packets arriving out of order ===
+
+The out of order packets proportion is computed using the following  
formula:
+
+{{{
+DupAcksIn/AckPktsIn
+}}}
+
+where:
+ * *!DupAcksIn* - The number of duplicate ACKs received
+ * *!AckPktsIn* - The number of valid pure ACKs received
+
+=== Average round trip time (Latency/Jitter) ===
+
+The average round trip time is computed using the following formula:
+
+{{{
+SumRTT/CountRTT
+}}}
+
+where:
+ * *SumRTT* - The sum of all sampled round trip times
+ * *CountRTT* - The number of round trip time samples