Cisco is one of the most successful companies in the United States. Founded by a professor and his wife from Stanford University in 1984, the first router was produced in 1986, which enabled different types of networks to reliably connect with each other, and set off a communication revolution. Cisco invests more than $4 billion annually in technology research and development. In the past 20 years, Cisco has almost become the synonym of "Internet, network application, productivity". Cisco has become the market leader in every field it enters