Network classless time protocol based on clock offset optimization

Orner Gurewitz, Israel Cidon, Moshe Sidi

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Time synchronization is critical in distributed environments. A variety of network protocols, middleware and business applications rely on proper time synchronization across the computational infrastructure and depend on the clock accuracy. The Network Time Protocol (NTP) is the current widely accepted standard for synchronizing clocks over the Internet. NTP uses a hierarchical scheme in order to synchronize the clocks in the network. In this paper we present a novel non-hierarchical peer-to-peer approach for time synchronization termed CTP - Classless Time Protocol. This approach exploits convex optimization theory in order to evaluate the impact of each clock offset on the overall objective function. We define the clock offset problem as an optimization problem and derive its optimal solution. Based on the solution we develop a distributed protocol that can be implemented over a communication network, prove its convergence to the optimal clock offsets and show its properties. For compatibility, CTP may use the packet format and number of measurements used by NTP. We also present methodology and numerical results for evaluating and comparing the accuracy of time synchronization schemes. We show that the CTP outperforms hierarchical schemes such as NTP in the sense of clock accuracy with respect to a universal clock.

Original languageEnglish
Pages (from-to)876-888
Number of pages13
JournalIEEE/ACM Transactions on Networking
Issue number4
StatePublished - 1 Aug 2006
Externally publishedYes


  • Classless time protocol (CTP)
  • Estimation
  • Measurements
  • Network management
  • One-way delay
  • Time synchronization
  • UTC

ASJC Scopus subject areas

  • Software
  • Computer Science Applications
  • Computer Networks and Communications
  • Electrical and Electronic Engineering


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