SPTP — The properties of timing devices

"• The properties of timing devices are listed, but some of them are not explained, and
no clue is given as to measure or represent them. This is the case for stability and skew.
In particular, the relationship between skew and offset should be explicit.
• Last paragraph but one, last sentence, definition of drift: the definition does not appear
very clear to me: what can be the relative frequency of a clock between two successive
ticks? Is not the drift simply measured by (the absolute value of) the difference of fre-quencies?
(Frequency taken with the usual definition, one over the period.)
• Last paragraph, last sentence: It says that a timer is always associated with a particular
clock; this is not explicit on the diagram of fig. 5-3; in fact, according to this diagram,
a timer is indirectly and implicitly associated with (at least) two clocks, one coming
through inheritance from TimingMechanism (the reference clock) and the other com-ing
through the association with TimeValue, which is itself associated with a refer-ence
clock; there is no constraint to express that these two clocks should be the same.
Should they?"

see above