Here is a link to a very accurate bandwidth measurement tool. Unlike many of the bandwidth tools out there, this one will report the upload bandwidth, in addition to the download bandwidth. The result will help identify where the bottleneck resides.
It uses Java. If you see a gray box instead of a yellow window, you need to install, or update the Java on your computer. The update can be found at
Below is a example of the output when the Windows XP default TCP window size of 17,520 is used. The second example shows the throughput after the window size is increased to 61,440 bytes. An increase of almost 300kbps is achieved by making this change. If you want to see a video clip of how to make this change, check out:
Example output from Web100 bandwidth tool:
Before Windowsize change
TCP/Web100 bandwidth test v4.12
click START to begin
running 10s outbound test... 634 Kbs outbound
running 10s inbound test... 789 Kbs inbound
Web100 Inbound Summary:
Packets to your host: 708 of size 1460 bytes
average RTT: 160.0 ms minimum RTT: 150.0 ms
Maximum Expected Bandwidth: 0 Mbs
Inbound limits:
congestion 7% server: 0% your host: 92%
Good Data Stream--No retransmits!
Your host's receive buffer: 17520 bytes
Server's send buffer: 0 bytes
receive buffer: 65535 bytes
Buffer sizes are very important in determining
network performance. Larger buffer sizes can
help increase thruput. If your buffer is smaller
than the remote host, you should investigate
increasing your socket buffer sizes.
Web100 reports Tweakable Settings as:
RFC 2018 Selective Acknowledgment: ON
RFC 1323 Time Stamping: OFF
RFC 1323 Window Scaling: OFF
After Windowsize Change
TCP/Web100 bandwidth test v4.12
click START to begin
running 10s outbound test... 573 Kbs outbound
running 10s inbound test... 1048 Kbs inbound
Web100 Inbound Summary:
Packets to your host: 955 of size 1460 bytes
average RTT: 450.0 ms minimum RTT: 150.0 ms
Maximum Expected Bandwidth: 3 Mbs
Inbound limits:
congestion 16% server: 0% your host: 83%
Good Data Stream--No retransmits!
Your host's receive buffer: 62780 bytes
Server's send buffer: 0 bytes
receive buffer: 65535 bytes
Buffer sizes are very important in determining
network performance. Larger buffer sizes can
help increase thruput. If your buffer is smaller
than the remote host, you should investigate
increasing your socket buffer sizes.
Web100 reports Tweakable Settings as:
RFC 2018 Selective Acknowledgment: ON
RFC 1323 Time Stamping: OFF
RFC 1323 Window Scaling: OFF
Mike Pennacchi - mpennac
It uses Java. If you see a gray box instead of a yellow window, you need to install, or update the Java on your computer. The update can be found at
Below is a example of the output when the Windows XP default TCP window size of 17,520 is used. The second example shows the throughput after the window size is increased to 61,440 bytes. An increase of almost 300kbps is achieved by making this change. If you want to see a video clip of how to make this change, check out:
Example output from Web100 bandwidth tool:
Before Windowsize change
TCP/Web100 bandwidth test v4.12
click START to begin
running 10s outbound test... 634 Kbs outbound
running 10s inbound test... 789 Kbs inbound
Web100 Inbound Summary:
Packets to your host: 708 of size 1460 bytes
average RTT: 160.0 ms minimum RTT: 150.0 ms
Maximum Expected Bandwidth: 0 Mbs
Inbound limits:
congestion 7% server: 0% your host: 92%
Good Data Stream--No retransmits!
Your host's receive buffer: 17520 bytes
Server's send buffer: 0 bytes
receive buffer: 65535 bytes
Buffer sizes are very important in determining
network performance. Larger buffer sizes can
help increase thruput. If your buffer is smaller
than the remote host, you should investigate
increasing your socket buffer sizes.
Web100 reports Tweakable Settings as:
RFC 2018 Selective Acknowledgment: ON
RFC 1323 Time Stamping: OFF
RFC 1323 Window Scaling: OFF
After Windowsize Change
TCP/Web100 bandwidth test v4.12
click START to begin
running 10s outbound test... 573 Kbs outbound
running 10s inbound test... 1048 Kbs inbound
Web100 Inbound Summary:
Packets to your host: 955 of size 1460 bytes
average RTT: 450.0 ms minimum RTT: 150.0 ms
Maximum Expected Bandwidth: 3 Mbs
Inbound limits:
congestion 16% server: 0% your host: 83%
Good Data Stream--No retransmits!
Your host's receive buffer: 62780 bytes
Server's send buffer: 0 bytes
receive buffer: 65535 bytes
Buffer sizes are very important in determining
network performance. Larger buffer sizes can
help increase thruput. If your buffer is smaller
than the remote host, you should investigate
increasing your socket buffer sizes.
Web100 reports Tweakable Settings as:
RFC 2018 Selective Acknowledgment: ON
RFC 1323 Time Stamping: OFF
RFC 1323 Window Scaling: OFF
Mike Pennacchi - mpennac