# Traffic load 與 buffer size 的關係 (QoS) Author: WhoAmI Date: 20230126 email: kccddb@gmail.com Copyright: CC BY-NC-SA <style> .blue { color: blue; } .bgblue { color: blue; font-size: 24px; font-weight: bold; } .red { color: red; font-size: 24px; font-weight: bold; } h1 {text-align: center;} h2 {text-align: center;} </style> input rate: $\lambda$ output rate: $\mu$ ![](https://i.imgur.com/vuj39MT.png) ![](https://i.imgur.com/ctq8Eto.png) An M/M/1 queue is a stochastic process whose state space is the set {0,1,2,3,...} where the value corresponds to the number of customers in the system, including any currently in service. Arrivals occur at rate λ according to a Poisson process and move the process from state i to i + 1. Service times have an exponential distribution with rate parameter μ in the M/M/1 queue, where 1/μ is the mean service time. **utilization $\rho=\frac{\lambda}{\mu}$** ![](https://i.imgur.com/EMWRlkG.jpg) ![](https://i.imgur.com/5ZANUQg.jpg) ![](https://i.imgur.com/K02EMkd.jpg) :::info 當 $\rho=\lambda/\mu$ 增加 惡化更快 (通常非線性) ::: <h2>Input Queue</h2> ![](https://i.imgur.com/NX2bdCM.jpg) ![](https://i.imgur.com/JkZ4EVx.jpg) <h2> Output Queue</h2> ![](https://i.imgur.com/5gwR3GF.png) ![](https://i.imgur.com/Cz5JaYv.png) ![](https://i.imgur.com/pe2XQ2j.jpg)