Delay, Loss, and Throughput in Packet-Switched Networks
delay
As a packet travels from one node (host or router) to the subsequent node (host or router) along this path, the
packet suffers from several types of delays at each node along the path.
The most important of these delays are the nodal processing delay, queuing delay, transmission delay, and propagation delay
-
transmission delay：假设数据包以先到先得的方式传输，这在数据包交换网络中很常见，那么我们的数据包只有在传输之前到达的所有数据包都已到达后才能传输。The transmission delay is N *L/R. 见前边博客，一个包跨越一个链路的延迟是L/R。
-
propagation delay：将bits推入链路后，它需要传播到路由器 B。从链路开头传播到路由器 B 所需的时间是传播延迟。该位以链路的传播速度传播。传播速度取决于链路的物理介质（即光纤、双绞线铜线等）
传播延迟为 d/s，其中 d 是路由器 A 和路由器 B 之间的距离，s 是链路的传播速度。
If we let dproc , dqueue , dtrans , and dprop denote the processing, queuing, transmis-
sion, and propagation delays, then the total nodal delay is given by
Loss
the queue capacity is finite, packet delays do not really approach infinity as the traf-
fic intensity approaches 1. Instead, a packet can arrive to find a full queue. With no
place to store such a packet, a router will drop that packet; that is, the packet will be
lost.
Throughput
