Apple quietly rolled out a "broadband tuner" application today, which is geared toward speeding up connections on high latency internet connections.
The installer increases the default values for the size of the TCP send and receive buffers. With larger buffers more data can be in transit at once. A startup configuration file is also updated so that these changes will persist across restarts.
The system parameters are sysctl variables that are set as follows:
This change has a system wide effect and is applied even if the network is not high speed connection with a high latency, with the exception of modem connections for which the system uses small default TCP buffer sizes.