bulk transfer

I have a question here,

I have have a device support bulk end point.  The capacity of the end point is 16 bytes.

the device is receiving data from host.  If the data packet is less than 16 bytes, the device knows it is the end of transfer.

My question is if the host send exactly 16 bytes of data.  How does device know it is the end of transfer.

Thanks,

Send a zero packet identify the end of transfer

Thanks Jinghuiren,

So on the MS XP host.  who is in charge of sending the zero length packet?  the microsft host controler driver or my own device driver?