1-持久和非持久CSMA之间的区别

先决条件 – 载波侦听多路访问 (CSMA)
1. 1-持久CSMA：
在 1-persistent CSMA 中，站点不断地侦听信道以检查其状态，即空闲或忙碌，以便它可以传输数据。在信道忙的情况下，站将等待信道变为空闲。当站点发现空闲信道时，它以概率1 无延迟地向信道传输帧。由于概率1，它被称为1-持久CSMA。这种方法的问题是碰撞的可能性很大，因为两个或多个站点可以在空闲状态下找到信道并同时传输帧。在发生冲突时，站必须等待随机时间让信道空闲并重新开始。

图 – 1 – 持久性 CSMA

2. 非持久性 CSMA ：
在非持久性 CSMA 中，具有要发送的帧的站仅感知信道。在空闲通道的情况下，它将立即向该通道发送帧。如果发现信道忙，它将等待固定的时间量并再次感知站的状态是空闲还是忙。在这种方法中，当站点检测到前一次传输结束时，它不会为了捕获信道而立即感知信道。这种方法减少了冲突的机会，但降低了网络的效率。

图 –非持久性 CSMA

1-persistent 和 Non-persistent CSMA 的区别：

Basis	1-persistent CSMA	Non-persistent CSMA
Carrier Sense	When channel is idle it will send with probability 1.	When channel is idle it will send frame.
Waiting	It will continuously sense channel for transmission of frames.	It will wait for random amount of time to check carrier.
Chance of Collision	In this method, there are highest number of collisions observed.	In this method, chance of collision are less than in 1-persistent.
Utilization	It’s utilization is above ALOHA because frames are sent only when channel is found in idle state.	It’s utilization is above 1-persistent because in this all stations constantly check for channel at same time.
Delay Low Load	It is small because frames are sent only in idle state.	It is longer than 1-persistent as it only checks randomly when channel is busy.
Delay High Load	It is high due to collision.	It is longer than 1-persistent because stations check randomly when channel is busy.