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Preventing the collision of requests from slave clocks in the Precision Time Protocol (PTP)

Ciuffoletti, Augusto (2011) Preventing the collision of requests from slave clocks in the Precision Time Protocol (PTP). IEEE Transactions on Instrumentation and Measurement, 60 (6). pp. 2096-2103. ISSN 0018-9456

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    SUMMARY The Precision Time Protocol (PTP) distributes a time reference across a network: it specifically addresses demanding environments, where it can reach sub microsecond precision using appropriate technologies. Its scalability is primarily limited by packet delay variations induced by packet collisions. While it is possible to avoid collisions with non-PTP packets using traffic management technologies, collision between PTP packets is an open problem in large systems with critical clock precision requirements. We propose a coordination algorithm that avoids the occurrence of such collisions. It assumes that the timing reference source, the master clock, can send a packet in multicast to the slaves: this is not a restrictive hypotesis, since PTP itself takes advantage of this kind of connectivity, and it is also compatible with typical wireless environments. The algorithm operates without introducing additional traffic, it ensures an upper bound to the time between two successive synchronizations of any given slave, it does not alter the structure of the standard PTP messages, it envisions a dynamic number of slaves, it tolerates the replacement of the master with a hot spare in case of failure, and does not rely on specialized hardware. The algorithm has a footprint that does not insist on activities that are already time sensitive, and its operation is mostly concentrated on the master. The algorithm inherits security and fault tolerance limits from PTP: in particular this refers to malicious nodes, and to broken devices that may jam the network.

    Item Type: Article
    Additional Information: Presentation available at http://www.slideshare.net/AugustoCiuffoletti/collision-avoidance-using-a-wandering-token-in-the-ptp-protocol
    Uncontrolled Keywords: precision time protocol, IEEE1588, clock synchronization, packet collision, coordination protocol, token routing, random graph, wandering token
    Subjects: Area09 - Ingegneria industriale e dell'informazione > ING-INF/03 - Telecomunicazioni
    Area09 - Ingegneria industriale e dell'informazione > ING-INF/05 - Sistemi di elaborazione delle informazioni
    Area09 - Ingegneria industriale e dell'informazione > ING-INF/07 - Misure elettriche e elettroniche
    Divisions: Dipartimenti (until 2012) > DIPARTIMENTO DI INFORMATICA
    Depositing User: Augusto Ciuffoletti
    Date Deposited: 13 Jan 2012 10:16
    Last Modified: 13 Jan 2012 10:16
    URI: http://eprints.adm.unipi.it/id/eprint/1246

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