请教大侠:NDIS驱动开发 lookahead是什么意思????急!!20分!!!

   请问一下的lookahead是什么意思,作什么用的?
  (以下是ddk文档中的一段话,我读了好几遍还是不明白:(,请大侠指教!)

OID_GEN_MAXIMUM_LOOKAHEAD
 
   MiniportQueryInformation must return how many bytes of lookahead data the NIC can provide, that is, the initial transfer capacity of the NIC.
Even if a driver supports multipacket receives and, therefore, will indicate an array of pointers to fully set up packets, MiniportQueryInformation must supply this information. Such a driver should return the maximum packet size it can indicate.  

:(
请会的大侠说一两句也行啊,我一定给分的.