The addresses, encapsulated as source and destination in the IP datagrams header, are used to transmit the datagram to their destination, called routing. Basically, this creates two scenarios
地址（在 IP 数据报头中封装为源和目的地地址）用来将数据报传输到其目的地，这个过程称为 路由。
2
No matter which type it belongs to, the purpose of routing protocol is the same: send datagram to destination.
不管是哪个类型，每一种路由选择协议的目的都是一样的：把数据报送到目的地。
3
For traditional IP network, the currently deployed routing scheme is focused on constructing end-to-end connectivity which usually supports only one type of datagram service.