缺点是,如果网络繁忙时碰撞的数量急剧上升,每包会发生碰撞。ALOHAnet的最大信道利用率是18%左右,和任何试图推动网络在这只会增加碰撞,和整体数据吞吐量会下降,这种现象称为拥塞崩溃。开槽阿罗哈,一个集中的时钟发出小时钟周期包外围站。边远站点只被允许把数据包后立即收到一个时钟周期。如果只有一个数据包发送站,这可以保证永远不会有一个数据包的碰撞。另一方面,如果有两个车站数据包发送,该算法保证会有碰撞,和整个槽周期到下一个时钟周期都被浪费了。与随机过程的数学,可以证明该协议迎宾通道的总体利用率的两倍,仅仅通过减少碰撞的1/2的概率。代替低利用率略有改变这个系统的改进的避碰在繁忙的网络,这成为了标准以太网CSMA / CD和我们称之为技术,载波监听多路访问,碰撞检测。
On the downside, if the network gets busy the number of collisions can rise dramatically to the point where every packet will collide. For ALOHAnet the maximum channel utilization was around 18%, and any attempts to drive the network over this would simply increase collisions, and the overall data throughput would actually decrease, a phenomenon known as congestion collapse.With Slotted ALOHA, a centralized clock sends out small clock tick packets to the outlying stations. Outlying stations were only allowed to send their packets immediately after receiving a clock tick. If there is only one station with a packet to send, this guarantees that there will never be a collision for that packet. On the other hand if there are two stations with packets to send, this algorithm guarantees that there will be a collision, and the whole of the slot period up to the next clock tick is wasted. With the mathematics of random processes, it is possible to demonstrate that this protocol does double the overall ALOHA channel utilization, simply by reducing the probability of collisions by one-half.Instead of low utilization a slight change of this system improved collision avoidance on busy networks and this became the standard for Ethernet and we call this technique as CSMA/CD, carrier sense, multiple access, and collision detection.