随着片上多处理器系统核数的增加,当前一致性协议上存在的许多问题使共享存储系统复杂而低效.目前一些一致性协议极其复杂,例如MESI(modified exclusive shared or invalid)协议,存在众多的中间状态和竞争.并且这些协议还会导致额外失...随着片上多处理器系统核数的增加,当前一致性协议上存在的许多问题使共享存储系统复杂而低效.目前一些一致性协议极其复杂,例如MESI(modified exclusive shared or invalid)协议,存在众多的中间状态和竞争.并且这些协议还会导致额外失效通信,以及大量记录共享信息的目录存储开销(目录协议)或广播消息的网络开销(监听协议).对数据无竞争的程序实现了一种简单高效一致性协议VISU(valid/invalid states based on self-updating),这种协议基于自更新操作(self-updating)、只包含2个稳定状态(valid/invalid).所设计的两状态VISU协议消除了目录和间接事务.首先基于并行编程的数据无竞争(data race free, DRF)模型,采用在同步点进行自更新共享数据来保证正确性.其次利用动态识别私有和共享数据的技术,提出了对私有数据进行写回、对共享数据进行写直达的方案.对于私有数据,简单的写回策略能够简化不必要的片上通信.在L1 cache中,对于共享数据的写直达方式能确保LLC(last level cache)中数据最新从而消除了几乎所有的一致性状态.实现的VISU协议开销低、不需要目录、没有间接传输和众多的一致性状态,且更加容易验证,同时获得了与MESI目录协议几乎相当甚至更优的性能.展开更多
Two standards for security of WLAN,IEEE 802.11 i and WAPI,are introduced,and some shortcomings of them are pointed out.Based on hash chains technique to construct identity authentication tokens, a new authentication i...Two standards for security of WLAN,IEEE 802.11 i and WAPI,are introduced,and some shortcomings of them are pointed out.Based on hash chains technique to construct identity authentication tokens, a new authentication infrastructure for WLAN is proposed,in which AS authenticates the main entities -STAs in the foremost time.Properties of the proposed scheme are discussed,including security, efficiency and feasibility etc.Compared with 802. 11 i and WAPI,the proposed scheme not only improves efficiency by reducing cost on computation and communication,but also promotes security property -availability by mitigating DoS attacks to AP and AS.At the same time,a self-updating hash chain technique is presented that is embedded in the proposed infrastructure to solve the length limitation of traditional hash chain.展开更多
文摘随着片上多处理器系统核数的增加,当前一致性协议上存在的许多问题使共享存储系统复杂而低效.目前一些一致性协议极其复杂,例如MESI(modified exclusive shared or invalid)协议,存在众多的中间状态和竞争.并且这些协议还会导致额外失效通信,以及大量记录共享信息的目录存储开销(目录协议)或广播消息的网络开销(监听协议).对数据无竞争的程序实现了一种简单高效一致性协议VISU(valid/invalid states based on self-updating),这种协议基于自更新操作(self-updating)、只包含2个稳定状态(valid/invalid).所设计的两状态VISU协议消除了目录和间接事务.首先基于并行编程的数据无竞争(data race free, DRF)模型,采用在同步点进行自更新共享数据来保证正确性.其次利用动态识别私有和共享数据的技术,提出了对私有数据进行写回、对共享数据进行写直达的方案.对于私有数据,简单的写回策略能够简化不必要的片上通信.在L1 cache中,对于共享数据的写直达方式能确保LLC(last level cache)中数据最新从而消除了几乎所有的一致性状态.实现的VISU协议开销低、不需要目录、没有间接传输和众多的一致性状态,且更加容易验证,同时获得了与MESI目录协议几乎相当甚至更优的性能.
基金supported by the NNSF of China(No.90204015, 60473021)the Key Technologies Research and Development Program of Henan Province of China(No.0524220044,062426001)the Research Found of HAUT of China(No.0401009, 050211,050215,050216)
文摘Two standards for security of WLAN,IEEE 802.11 i and WAPI,are introduced,and some shortcomings of them are pointed out.Based on hash chains technique to construct identity authentication tokens, a new authentication infrastructure for WLAN is proposed,in which AS authenticates the main entities -STAs in the foremost time.Properties of the proposed scheme are discussed,including security, efficiency and feasibility etc.Compared with 802. 11 i and WAPI,the proposed scheme not only improves efficiency by reducing cost on computation and communication,but also promotes security property -availability by mitigating DoS attacks to AP and AS.At the same time,a self-updating hash chain technique is presented that is embedded in the proposed infrastructure to solve the length limitation of traditional hash chain.
