NTP version 4 Release Notes HP-UX 11i v3 (5900-3073, March 2013)

IPv6 support
NTP v4 supports IPv6 in addition to the default support for the IPv4 address family. If a host name
is expected, an ntpq-4 qualifier preceding the host name forces DNS resolution to the IPv4
namespace, while an ntpq-6 qualifier forces DNS resolution to the IPv6 namespace.
Quicker start up of NTP daemon
The behavior of the NTP daemon at start up has considerably improved. Now, the time to measure
the frequency and correct an initial offset error when the daemon is started for the first time is less
than ten minutes.
Upon restart, it takes less than five minutes to reduce the initial offset to less than one millisecond
without adversely affecting the frequency. This avoids a subsequent frequency correction, which
might take up to several hours.
Interleaved mode
Interleaved mode is used in NTP Symmetric and Broadcast modes only. It is designed to improve
the accuracy by minimizing errors due to queuing and transmission delays.
To activate the Interleaved mode, enter the xleave option with the peer or broadcast
configuration commands in ntp.conf.
peer address xleave
broadcast address xleave
A broadcast server configured for the Interleaved mode is transparent to ordinary broadcast clients.
Therefore, both ordinary and interleaved broadcast clients can use the same packets. If the peer
is not capable of operation in the Interleaved mode, an interleaved symmetric active peer
automatically switches to ordinary symmetric mode.
The interleaved modes have the same resistance to lost packets, duplicate packets, packets crossed
in flight, and protocol restarts as the ordinary modes.
Huff-n'-Puff filter
The Huff-n'-Puff Filter is designed to avoid large errors with DSL circuits and highly asymmetrical
traffic, when downloading large files.
In the scenario, where a considerable amount of data is downloaded or uploaded using DSL or
telephone modem lines, timekeeping quality is seriously degraded. This occurs because the traffic
volume, resulting in queuing delays, on the upload and download directions of transmission can
be different. In many cases, the apparent time errors are so large as to exceed the step threshold
and a step correction can occur during and after the data transfer.
The Huff-n'-Puff Filter is designed to correct the apparent time offset in the case of scenario just
described. To correct this time offset, Huff-n'-Puff Filter depends on the propagation delay during
particular hours when no traffic is present. The filter remembers the minimum delay over the most
recent interval measured usually in hours. Under conditions of large delay, the filter corrects the
apparent offset using the sign of the offset and the difference between the apparent delay and
minimum delay. The name of the filter reflects the negative (Huff) and positive (Puff) correction,
which depends on the sign of the offset. The filter is activated by the tinker huffpuff command.
tinker huffpuff huffpuff: Specifies the huff-n'-puff filter span, which determines the most
recent interval the algorithm searches for a minimum delay. The lower limit is 900 seconds (15
minutes), but a more reasonable value is 7200 seconds (2 hours).
Orphan mode
Orphan mode provides an automatic, subnet-wide synchronization feature with multiple sources.
It provides a reliable backup in isolated networks or when Internet sources become unavailable.
Utilities 7