What is Stratum?
Stratum is a term that means different things depending on the context. In the telecommunications industry stratum level is indicative of oscillator performance. It refers to the holdover performance of the oscillator in the event of loss of synchronization. A Stratum 1 clock has an accuracy of 1.0 x 10-11, Stratum 2 has an accuracy of 1.6 x 10-8, Stratum 3 has an accuracy of 4.6 x 10-6, and Stratum 4 has an accuracy of 3.2 x 10-5. In the world of NTP, Stratum is defined in RFC 1305. NTP uses a hierarchical structure in which Stratum 0 is the reference clock, linked via a time signal, to a reliable source of UTC. Stratum 1 is the time server with a direct link to the reference clock. Stratum 2 is a client that receives time over a network connection from a Stratum 1 clock. Stratum 3 is a client that receives time from a Stratum 2 clock. And so on, up to Stratum 15. For more details on strata in the NTP world, click here.
