UDP协议下支持透明计算模式的RTO算法  

RTO algorithm for transparent computing systems

作　　者：王晓辉[1] 夏楠[2] 韦理[1] 

机构地区：[1]清华大学计算机科学与技术系,北京100084 [2]合肥工业大学计算机网络系统所,合肥230009

出　　处：《清华大学学报（自然科学版）》2007年第10期1696-1699,共4页Journal of Tsinghua University(Science and Technology)

基　　金：国家"八六三"高技术项目(2004AA111020;2004AA114062)

摘　　要：NSAP(network storage access protocol)协议是透明计算系统采用的核心协议,而RTO(retransmission timeout)算法是保证NSAP协议可靠性和效率的重要技术。现有的RTO算法而在透明计算环境下性能较差。该文通过分析NSAP协议报文RTT(round trip time)的统计特性,在Eifel算法的基础上,提出增强的Eifel算法(E-Eifel)。E-Eifel算法选择计算出的RTT最大值和Eifel算法的RTO值中较大的一个作为自己的RTO值。实验表明E-Eifel算法可以显著降低伪超时数,提高NSAP协议的数据传输效率,从而提高透明计算系统的性能。Network storage access protocol （NSAP） is the core protocol used in transparent computing systems with the retransmission timeout （RTO） algorithm used as an important technology to improve the reliability and efficiency of the NSAP. However, current RTO algorithms do not provide adequate performance in transparent computing environments. The statistical RTT characteristics o{ NSAP packets were analyzed to develop an enhanced Eifel algorithm which separates the RTT into a common RTT and a pulsed RTT. The algorithm calculates the mean of a number of recent RTTs to distinguish the pulsed RTT from the others, and then identifies the maximum RTT of those RTTs except for the pulsed RTT. The algorithm then selects the larger of the maximum RTT and the Eife＇s RTO as its own RTO. Test results indicate that the algorithm reduces the number of spurious timeouts and improves transport efficiency to provide good performance in transparent computing systems.

关 键 词：重传超时 Jacobson算法 Elfel算法 

分 类 号：TP393[自动化与计算机技术—计算机应用技术]