The attached patch improves the net plugin in three ways:
1) adds an option to the configuration to set the interface to be monitored; the configuration variable is called "Interface"
2) adds an option to the configuration to set the polling interval time (in microseconds); the variable is called "PollingTime"
3) the tooltip shows interesting information: the upload and download speed, and the total data transfered so far.
Please, if the code is ok, apply the patch to upstream.