stratum

A convention established to indicate the accuracy of each time server. It is defined by a number, with the topmost level (primary servers) assigned as 1 and each level downward (secondary servers) in the hierarchy assigned as one greater than the preceding level. For example, a stratum 3 server is at a higher stratum than a stratum 2 server, and at a lower stratum than a stratum 4 server. Therefore, the stratum 3 time server is more accurate than the stratum 4 server, but less accurate than the stratum 2 server. Maximum allowed strata is 15.