If the line speed is 9600 bits/sec, with 8 bits per byte, plus 1 start bit and 1 stop bit, the line speed is 960 bytes/sec. Transferring a 1024-byte packet at this speed takes 1066 ms. If we're using the SLIP link for an interactive application, along with an application such as FTP that sends or receives 1024-byte packets, we have to wait, on the average, half of this time (533 ms) to send our interactive packet.
为什么我们平均需要等待533ms呢?
答案是根据假设,我们在使用SLIP连接,因为SLIP的数据帧没有协议信息,因此,发送某一个协议的数据时,就不能发送另一种协议的数据。所以使用SLIP时,我们的交互程序要么可以发送interactive packet(等待0ms),要么不能(要发送FTP数据,等待1066ms),因此平均下来就是要等待533ms了。