说明：  opnet的学习电子书，OPNET 是目前网络仿真 工具中的很好的一个，但是由于操作复杂，使用者一般需要半年或以上时间的培训和自行研究才能熟练地掌握
(Learning OPNET books, OPNET is currently the network simulationTool in a very good, but because the operation is complex, the user generally needs a half year or more time training and Research on its own can skillfully master)