NDT-DEV email list created

Revision: 595
Author:   

Date:     Fri Sep  2 06:32:38 2011
Log:      Feedback based modifications in the Link Type Detection  
Heuristics section.
http://code.google.com/p/ndt/source/detail?r=595

Modified:
 /wiki/NDTTestMethodology.wiki

=======================================
--- /wiki/NDTTestMethodology.wiki       Fri Sep  2 06:12:11 2011
+++ /wiki/NDTTestMethodology.wiki       Fri Sep  2 06:32:38 2011
@@ -200,7 +200,9 @@

 ==== DSL/Cable modem ====

-The link is treated as a DSL/Cable modem when all of the following  
conditions are met:
+The link is treated as a DSL/Cable modem when the sender isn't a  
bottleneck and the [NDTTestMethodology#Web100_measured_speed web100  
measured speed] is less than 2 Mbps and less than  
[NDTTestMethodology#Speed_estimate speed estimate].
+
+This means that all of the following conditions should be met:
  * The cumulative time spent in the 'Sender Limited' state *is less than  
0.6 ms*
  * The number of transitions into the 'Sender Limited' state *is 0*
  * The [NDTTestMethodology#Web100_measured_speed web100 measured speed]  
*is less than 2 Mbps*
@@ -208,7 +210,9 @@

 ==== IEEE 802.11 (!WiFi) ====

-The link is treated as a wireless one when all of the following conditions  
are met:
+The link is treated as a wireless one when the  
[NDTTestMethodology#DSL/Cable_modem DSL/Cable modem] heuristic gives  
negative results, the receiver is a bottleneck and the  
[NDTTestMethodology#Web100_measured_speed web100 measured speed] is less  
than 5 Mbps but the [NDTTestMethodology#Speed_estimate speed estimate] is  
greater than 50 Mibps.
+
+This means that all of the following conditions should be met:
  * The heuristic for DSL/Cable modem link *gives negative results*
  * The cumulative time spent in the 'Sender Limited' state *is 0 ms*
  * The [NDTTestMethodology#Web100_measured_speed web100 measured speed]  
*is less than 5 Mbps*
@@ -218,20 +222,26 @@

 ==== Ethernet link (Fast Ethernet) ====

-The link is treated as an Ethernet link (Fast Ethernet) when all of the  
following conditions are met:
+The link is treated as an Ethernet link (Fast Ethernet) when the  
heuristics for !WiFi and DSL/Cable modem links give negative results, the  
[NDTTestMethodology#Web100_measured_speed web100 measured speed] is between  
3 and 9.5 Mbps and the connection is very stable.
+
+This means that all of the following conditions should be met:
  * The heuristics for !WiFi and DSL/Cable modem links *give negative  
results*
  * The [NDTTestMethodology#Web100_measured_speed web100 measured speed]  
*is less than 9.5 Mbps*
  * The [NDTTestMethodology#Web100_measured_speed web100 measured speed]  
*is greater than 3 Mbps*
  * The S2C throughput test measured speed *is less than 9.5 Mbps*
- * The proportion of the number of multiplicative downward congestion  
window adjustments to the total number of segments sent *is less than 1%*
+ * The [NDTTestMethodology#Packet_loss packet loss] *is less than 1%*
  * The proportion of the duplicate ACKs received to the overall number of  
valid pure ACKs received *is less than 3.5%*

+==== Known limitations ====
+
+The [NDTTestMethodology#DSL/Cable_modem DSL/Cable modem] heuristic appears  
to be broken now because the DSL/Cable modems commonly go above 2Mbps  
nowadays.
+
 === Faulty Hardware Link Detection ===

 A bad cable (faulty hardware link) is detected when all of the following  
conditions are met:
  * The [NDTTestMethodology#Packet_loss packet loss] multiplied by 100 and  
divided by the [NDTTestMethodology#Total_test_time_in_seconds total test  
time in seconds] *is greater than 15*
  * The  
[NDTTestMethodology#'Congestion_Limited'_state_time_share 'Congestion  
Limited' state time share] divided by the  
[NDTTestMethodology#Total_test_time_in_seconds Total test time in seconds]  
*is greater than 0.6* (*WARNING: this condition cannot be met*)
- * The proportion of the number of multiplicative downward congestion  
window adjustments to the total number of segments sent *is less than 1%*
+ * The [NDTTestMethodology#Packet_loss packet loss] *is less than 1%*
  * The maximum slow start threshold, excluding the initial value, *is  
greater than 0*

 === Full/Half Link Duplex Setting ===