NDT-DEV email list created

Revision: 559
Author:   

Date:     Tue Aug 30 02:59:30 2011
Log:      Added description of the Middlebox Test.
http://code.google.com/p/ndt/source/detail?r=559

Modified:
 /wiki/NDTTestMethodology.wiki

=======================================
--- /wiki/NDTTestMethodology.wiki       Mon Aug 29 08:04:07 2011
+++ /wiki/NDTTestMethodology.wiki       Tue Aug 30 02:59:30 2011
@@ -27,6 +27,32 @@
 == Performed tests ==

 === Middlebox Test ===
+
+The middlebox test is a short throughput test from the server to the  
client with a limited CWND to check for a duplex mismatch condition.  
Moreover, this test uses a pre-defined MSS value to check if any  
intermediate node will modify its connection settings.
+
+A detailed description of all of the SFW protocol messages can be found in  
the [NDTProtocol#Middlebox_test NDT Protocol document].
+
+As a first step the server binds an ephemeral port and notify the client  
about this port number. The server also sets MSS on this port to 1456  
(strange value).
+
+Next, the client connects to the server's ephemeral port. When the  
connection is successfully established, the server sets the maximum value  
of the congestion window for this connection to `2 * (The current maximum  
segment size (MSS))`.
+
+In the next step the server starts a 5 seconds throughput test using the  
newly created connection. The NDT server sends packets as fast as possible  
(i.e. without any delays) during the test. These packets are written using  
the buffer of the following size: `(The current maximum segment size  
(MSS))`. If such buffer cannot be used, then the server uses a 8192 Byte  
one.
+
+The server can temporarily stop sending packets when the following formula  
is fulfilled:
+{{{
+BUFFER_SIZE * 16 < ((Next Sequence Number To Be Sent) - (Oldest  
Unacknowledged Sequence Number) - 1)
+}}}
+
+When the 5 seconds throughput test is over, the server sends the following  
results to the client:
+
+|| CurMSS || The current maximum segment size (MSS), in octets.||
+|| !WinScaleSent || The value of the transmitted window scale option if  
one was sent; otherwise, a value of -1. ||
+|| !WinScaleRcvd || The value of the received window scale option if one  
was received; otherwise, a value of -1. ||
+
+Next, the client sends its calculated throughput value to the server. This  
throughput value is calculated using the following value:
+{{{
+THROUGHPUT_VALUE = 8 * TRANSMITTED_BYTES / 1000 / TEST_DURATION_SECONDS
+}}}

 === Simple Firewall Test ===

@@ -42,6 +68,8 @@

 The test is finished after the connection will be accepted or the time  
limit will be exceeded. If the time limit is exceeded, the firewall  
probably exists somewhere on the end-to-end path. If there is a connection  
and the pre-defined string is properly transferred, then there is no  
firewall on the end-to-end path. The third possibility is that there is a  
successful connection, but the expected pre-defined string is not  
transferred. This case does not adjudicate about the firewall existence.

+In the last step the server sends its results to the client.
+
 The possible simple firewall test result codes:

 || *Value* || *Description* ||