Performance evaluation of PTPd, a IEEE 1588 implementation, on the x86 Linux platform for typical application scenarios

The paper introduces the results of performance evaluation of IEEE 1588 Clock Synchronization technology implementation on the x86 (Intel) Linux platform. First, the typical application scenarios of IEEE 1588 in modern distributed measurement systems are listed, and based on that test systems are derived for testing with different configurations. These test systems are 1) a full software implementation in which no hardware elements support IEEE 1588, 2) a partial IEEE 1588 aware system in which end nodes synchronizing clocks support hardware time stamping but network elements do not, and 3) a full IEEE 1588 aware solution in which both end nodes and network elements support the standard. The hardware assisted PTP implementation utilized for evaluation has been developed by the authors of the paper, and available from http://home.mit.bme.hu/~khazy/ptpd/. The hardware assisted implementation is based on the Linux operating kernel infrastructure specifically developed for high precision network time keeping available from the kernel version of 2.6.30, and uses Network Interface Cards with IEEE 1588 hardware time stamping available on the market. The initial results show that clock accuracy (master-slave clock difference) less than one microsecond is achievable with using a full IEEE 1588 implementation even in the case of high network traffic and slave node (a node that synchronizes its clock to a master clock) load in standard Linux. The paper also details how the implementation of the clock servo realized by fixed point arithmetic computations (quantization) effect the achievable clock accuracy and proposes enhancements to the current solution.