IEEE 802.1AS의 그랜드 마스터의 시간을 재선정하는 효율적인 방법

Abstract

In the Recent vehicle industry, Ethernet technology which has studied to use as backbone network of a vehicle is Audio/Video Bridge (AVB) standard. AVB provides time-synchronized low latency streaming service through the Ethernet. 802.1 AS protocol in AVB is the protocol which is synchronized the time between different nodes through Grand Master (GM) which is selected by the Best Master Clock Algorithm (BMCA). After synchronization is completed, the bridge providing the reference time transmits the synchronization message within timeout interval. If the synchronization message of GM is not received by another node within timeout interval, the protocol is synchronized by the time of the bridge which is selected a new GM in the network through BMCA. This method can occur the bunching error because of consecutive exchange of messages and increase the network traffic. Therefore, a delay time of reselection procedure is occurred. This thesis proposes an efficiency method to re-synchronize GM’s time. This proposed method is to use a table which indicates a pre-defined sequence of GM to reconfigure GM and port state of per bridge. Network configuration, which selects the device to provide a reference time for the time synchronization, performs comparison procedure of message repeatedly and creates a sequence table for each bridge. Especially, all devices in the network are optimized for the message time information field to perform a comparison process by using a common time. When reconfiguring the synchronization of the network by using the reference time of a new device, the method can reduce reselection process of grandmaster. As a result, the delay time and the traffic which are caused by conventional message exchange can be reduced to 54ms. In addition, this proposed method reduces the residence time of the bridge to prevent bunching of consecutive messages. Therefore, this paper proposes more efficiency method of reselecting the GM than the BMCA.