讲述为什么使用网络模拟器. 如协议验证. 控制试验条件. 花费低，耗时少，协同工作和复杂性好. 以及为什么使用NS.-talk about why the use of the network simulator. If agreement certification. Control test conditions. Low-cost and less time-consuming. teamwork and good complexity. and why the use of NS.