TSCclock: a low cost, robust, accurate software clock for networked computers
1:02:52
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2 years ago
Google Tech Talks
July 24, 2007
ABSTRACT
Accurate software clocks are essential for many aspects of networking, including both passive and active network measurement, real-time applications, and more generally, for tight distributed computation and service delivery. Best effort solutions using existing PC system clocks synchronised with the standard Network Time Protocol (NTP) algorithms are not robust enough, nor accurate enough for many purposes, whereas GPS based synchronisation is cash and effort intensive.
This talk will describe the TSCclock, a CPU oscillator based software clock with many intrinsic advantages, thanks to the high performance of modern off the shelf hardware. I will describe the principles and insights which make its synchronisation, based on client-server paradigm of timestamp exchange to a remote time server, extremely robust and more than an order of magnitude more accurate than the status quo, rivalling that of GPS based solutions in many respects. The performance of the current (client) implementation will be illustrated using months of data running live, using a detailed validation based on hardware capture cards, GPS, and modified kernels, and show comparisons with traditional NTP and GPS synchronised clocks. I will strongly emphasise the importance of separating absolute time from time differences, and show that for the latter, the clock is so robust that it can be disconnected from the server for weeks without ill effect. Finally some system aspects for the current implementation will be covered, for which we have packages for recent BSD and Linux distributions, and some comments on future features such a server side implementation and multi-processor support.Google Tech Talks
July 24, 2007
ABSTRACT
Accurate software clocks are essential for many aspects of networking, including both passiv...all »Google Tech Talks
July 24, 2007
ABSTRACT
Accurate software clocks are essential for many aspects of networking, including both passive and active network measurement, real-time applications, and more generally, for tight distributed computation and service delivery. Best effort solutions using existing PC system clocks synchronised with the standard Network Time Protocol (NTP) algorithms are not robust enough, nor accurate enough for many purposes, whereas GPS based synchronisation is cash and effort intensive.
This talk will describe the TSCclock, a CPU oscillator based software clock with many intrinsic advantages, thanks to the high performance of modern off the shelf hardware. I will describe the principles and insights which make its synchronisation, based on client-server paradigm of timestamp exchange to a remote time server, extremely robust and more than an order of magnitude more accurate than the status quo, rivalling that of GPS based solutions in many respects. The performance of the current (client) implementation will be illustrated using months of data running live, using a detailed validation based on hardware capture cards, GPS, and modified kernels, and show comparisons with traditional NTP and GPS synchronised clocks. I will strongly emphasise the importance of separating absolute time from time differences, and show that for the latter, the clock is so robust that it can be disconnected from the server for weeks without ill effect. Finally some system aspects for the current implementation will be covered, for which we have packages for recent BSD and Linux distributions, and some comments on future features such a server side implementation and multi-processor support.«
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