LT-Sync: A Lightweight Time Synchronization Protocol for P2P Networks based on IEEE1588

Abstract:
Fast increasing demand of high data rates implies new concepts for an efficient usage of available resources. Consequently, it is necessary to deploy an overlay-based network to control all steering data between the involved entities. Therefore, different architectures have been developed and tested. Especially for rapidly changing data, like spectrum usage information a method for time synchronization between all nodes is needed. Solutions like Parisync [1], Synchronization with bounded global and local skew [2], IEEE1588, the almost peer-to-peer synchronization [3], the Flooding Time Synchronization Protocol [4] or Probabilistic Clock Synchronization [5] vary in complexity and effectiveness. In this paper we introduce a simple lightweight time synchronization protocol which combines different ideas of all these approaches. Our solution can be seen as a hybrid between a hierarchical and distributed solution, means we will “split” the DHT into several areas with own head nodes. Each subset will be organized in a master-slave overlay structure. A so called root node will synchronize each subset via a periodical broadcast message. Additionally, each node will synchronize all entries in its neighbor-node list and parts of its fingertable. Transmission delays will be estimated via an IEEE1588 based calculation. We will present the first results in terms of accuracy and necessary overhead to deploy such a synchronization system. Finally we discuss the results and compare these with available systems.