面向用户的以太网可用性模型

带冲突检测的载波侦听多路访问协议(CSMA/CD)可以有效的解决竞争,提供高的吞吐量和低的延迟时间,并且成为了局域网设计中颇具吸引力的协议.基于计算机以太网CSMA/CD协议,面向用户探讨以太网可用度模型.通过定义工作站"拥塞状态"和"空闲状态",建立基于网络带宽、时隙的可用度模型.以信息成功发送概率作为衡量以太网可用性的指标.根据以太网中工作站的数量、平均字节长度、单机产生数据的速率以及单机数据重传速率对可用性影响的分析表明,随着局域网中接入的工作站的数量的增加在相同的时间内局域网的可用度将降低.随着数据产生率的升高,局域网的可用度将首先升高,当网络达到饱和后再增加数据产生率,局域网的可用度将降低.提高数据的重传率能够提高局域网的可用度.根据以上的分析,通过合理的设置网络参数,可以使局域网达到理想的可用度.

User oriented availability model of ethernet

Carrier sensing random multiple access with collision detection protocol(CSMA/CD) can solve competition effectively and provide high throughput and low delay,so it has become an attractive protocol to the designers of local area net(LAN).Based on LAN's CSMA/CD protocol analysis,the user oriented availability model of Ethernet is put forward.By defining the workstation operating mode as congesting model and idle mode,the availability model based on bandwidth and time slot is established.The probability of LAN sending packets successfully in specified time is defined as the availability measure of Ethernet.By analyzing the effect of different parameters which include the number of workstations in Ethernet,average length of packets,packets arrival rate and retransmission rate on availability,it is show that the LAN's availability will decrease synchronously with workstation number in network increasing.With packets arrival rate increasing,availability will improve to maximum firstly,then decrease subsequently.It also shows that increasing retransmission rate can improve LAN's availability.By setting parameters reasonably,the higher LAN's availability can be obtained.