NETWORK DRIVERS的问题

在看：
network drivers,design guide,part 1,charpter 3 ,section 5
packet structure 最后一段：

A BusMaster NIC driver that allocates shared memory for receiving incoming packets or protocol driver thar allocates memory for sending a packet must insure thar any buffer used to containing incoming or outgoning data is cache_aligned.This is neccessary so that the miniport can flush the buffer to assure coherency before sending a packet and flush a received buffer before indicating the data to an upper layer.

1）cache_aligned 是什么意思？
2）flush 又是什么意思？
谢了先！