hould expect a standalone 1.1 us phase holdover time of around 4~8 hours, not days or weeks. Of course, in combination with SyncE (assisted holdover), this time improves dramatically. The way to deliver robust, long-term holdover at reasonable cost is in the design of the network solution, not relying on gold-plated cap- abilities of the nodes in it. Note that there is both frequency holdover and phase holdover, although they are related because both holdover types rely upon the signal from the same oscillator. Frequency holdover is usually quite good, but it is phase holdover that quickly moves out of specification and causes issues. The reason that phase moves more quickly than frequency is that a small offset in frequency continues to accumulate phase error although the frequency might not wander any further. For example, fre- quency could be very stable with an offset of 10 ppb, which is still very accurate, but it means phase is accumulating 10 ns of phase error every second. There are two forms of holdover, which are normally discussed separately. Short-term holdover (transient response) is due to transients or temporary rearrangements in the network. This is a nor- mal situation due to everyday conditions in a network, links bouncing, node failover, fiber cuts, power outages, and SO on. This occurs regularly in a timing network and should be of little concern because timing can disappear for a short while with no impact on the radio network. The second form is long-term holdover, which is normally when the chain of traceability from the source of frequency, phase, and time to the end radio application in the radio site is broken. The long-term holdover measures the ability of a cell site to survive as an autonomous timing clock without those reference signals (this is what most people mean when they talk holdover). ITU-T specifications for clock performance (such as ITU-T G.8273.2) normally include separate requirements for transient response and long-term holdover, both with and without physical fre- quen