The default does not limit bandwidth. If the bandwidth approaches the limit you set, it is throttled back. If the server is rejecting requests when it is most active, increase this value. The max is 250. Signals when to write a logfile record.
Larger values improve performance at the expense of memory.
It waits for the batch size. Lower values are designed for less active servers. The greater of ConnectionTimeout or File size divided by this value, calibrated in seconds, is the maximum time that IIS will allow to send a file. An object remains in cache until it is overwritten. This value is optimal for most systems and changing it might impair performance.