摘要
针对现有交换机不能满足网络化测试应用实时性要求的问题,以及目前网络闭环时间传递方法存在的缺点与不足,设计了一种具有时间传递、时间检测、时钟再生功能的同步介质访问控制器(SMAC,Synchronized Medium Access Controller).同时设计了用于测量网络链路时延的SMAC时间帧结构.在此基础上对现有交换机结构进行了改进,给出了基于SMAC的以太网交换机结构设计方案,同时分析了基于SMAC的时间链路组成结构,提出了基于SMAC的开环时间传递方法,并进一步阐述了链路时延的测量过程.最后构建了实验平台,验证了基于SMAC的开环时间传递方法的有效性.实验结果表明,在经过一级SMAC交换设备的以太网环境中实现了25 ns的时间传递精度.
There exists the real-time problem when Ethernet switch is used in network-based measurement, and the shortcomings of closed loop time transmission. To solve those problems, a synchronized medium access controller （SMAC） was designed. The SMAC had the functions of time transmission, time detection and clock regeneration. Also the component of SMAC time frame used in measuring delay of transmission link was designed. On the basis of SMAC, Ethernet switch was improved and the structure of Ethernet switch composed of SMAC was given. After the time transmission link through SMAC was analyzed, an open loop time transmission method based on SMAC was presented, and then the measuring process of transmission link delay was set forth. At last an experimental platform was constructed to test the validity of the method, and the experimental result shows that time transfer accuracy within 25 nanoseconds is achieved by one SMAC switcher.
出处
《测试技术学报》
2008年第3期215-221,共7页
Journal of Test and Measurement Technology
基金
国防科工委"十一五"民用航天预研基金资助项目(C1320063103)
关键词
网络化测试
以太网交换机
同步介质访问控制器
时间传递
时间确定性
network-based measurement
ethernet switch
synchronized medium access controller
time transmission
time determinability
