Packet Delay Monitoring without a GPS

    This paper illustrates a technique to characterize one-way packet
delays. Such technique does not depend on external clock
synchronization facilities: instead, it computes the relative skew
of the two clocks, and uses this information to characterize one-way
packet delays.
    We focus on the applicability of such technique to a network mon-
itoring environment, and perform an extensive test that includes sec-
ond order clock frequency variations. We conclude that the approach
is especially suited to estimate jitter, and other "local" characteristics
of one-way delay variation. It can be helpful also to evaluate second
order parameters of one-way delay, like standard deviation, when sec-
ond order variations of clock frequency, usually due to temperature
variations, are compensated by hardware.
    This result makes one-way delay variations measurement widely
accessible to Internet hosts, at a cost which is overall comparable
with that of a ping.