ndt-users list created

[Rich Carlson <>]

Lize;

The speeds reported in the Test Results section are the measured speed 
achieved during this test.  The values reported in the More Details 
section are calculations of the maximum possible speed based on the 
buffer size and RTT.  TCP uses a sliding window to prevent buffer 
overruns and guarantee delivery of all data.  The send and receive 
buffers are set by the sender and receiver respectively.  The receiver 
returns an indication of the empty buffer space to the sender so it will 
stop  before overrunning this space.

The NDT report calculates the max possible speed by dividing the 
appropriate max buffer value (sender, receiver, congestion control) by 
the average RTT.  The theoretical limit is calculated using the Mathis 
et.al. formula where speed is a function of packet size, RTT, and packet 
loss.

Rich

On 5/1/2010 1:27 AM, 

 wrote:
> =============================Test Result=================================
> running 10s outbound test (client-to-server [C2S]) . . . . . 1.25Mb/s
> running 10s inbound test (server-to-client [S2C]) . . . . . . 9.54Mb/s
>
> ===================This is the report of More Details...==================
> The theoretical network limit is 246.82 Mbps
> The NDT server has a 126.0 KByte buffer which limits the throughput to 44.57 
> Mbps
> Your PC/Workstation has a 63.0 KByte buffer which limits the throughput to 
> 11.23 Mbps
> The network based flow control limits the throughput to 16.78 Mbps
>
> I don't know why the throughput of More Details dialog is different with the 
> result of C2S and S2C
> could somebody explain how does these values calculate or measure?