非HTTP协议定义的缓存机制
http://mp.weixin.qq.com/s?__biz=MzAxODE2MjM1MA==&mid=2651551769&idx=1&sn=3a422455b5cc240f8625842d31d81ab8&chksm=8025afd8b75226cec68e1e0e4b36334bb1d88e51a7fdba0cf7884d9f1d6597e4e4475cffaa38&mpshare=1&scene=23&srcid=0220Z2g84KSo54BvdfGmNCOM#rd
原文：http://www.cnblogs.com/aliwa/p/6420556.html