/* reset base time */
sort temporary list by increasing <$E[distance~index]>;
where <$E[distance~index]> represents the concatenation of the
distance and index fields and distance is the high-order field. The
filter dispersion <$Eepsilon sub sigma> is computed and included in the
peer dispersion. Note that for this purpose the temporary list is
already sorted.
<$Eepsilon sub sigma~<<-~0>;
for (i from NTP.SHIFT<196>1 to 0) /* compute
filter dispersion */
if (<$Eroman peer.dispersion sub index[i]~>>=~roman
NTP.MAXDISPERSE> or
<$E theta sub i~-~theta sub 0 ~>>~roman
NTP.MAXDISPERSE>)
<$Eepsilon sub sigma~<~><<-~( epsilon sub
sigma~+~roman NTP.MAXDISPERSE)~times~roman NTP.FILTER>;
else
<$Eepsilon sub sigma~<~><<-~( epsilon sub
sigma~+~ theta sub i~-~theta sub 0 )~times~roman NTP.FILTER>;
The peer offset <$Etheta sub 0>, delay <$Edelta sub 0> and dispersion
<$Eepsilon sub 0> are chosen as the values corresponding to the minimum-
distance sample; in other words, the sample corresponding to the first
entry on the temporary list, here represented as the 0th subscript.
<$Eroman peer.offset~<<-~theta sub 0>;
/* update peer variables */
<$Eroman peer.delay~<<-~delta sub 0>;
<$Eroman peer.dispersion~<<-~min ( epsilon sub 0~+~epsilon sub
sigma ,~roman NTP.MAXDISPERSE)>;
end clock-filter procedure
The peer.offset and peer.delay variables represent the clock offset and
roundtrip delay of the local clock relative to the peer clock. Both of
these are precision quantities and can usually be averaged over long
intervals in order to improve accuracy and stability without bias
accumulation (see Appendix H). The peer.dispersion variable represents
the maximum error due to measurement error, skew-error accumulation and
sample variance. All three variables are used in the clock-selection and
clock-combining procedures to select the peer clock(s) used for
synchronization and to maximize the accuracy and stability of the
indications.
Clock-Selection Procedure
The clock-selection procedure uses the peer variables <$ETHETA>,
<$EDELTA>, <$EEPSILON> and <$Etau> and is called when these variables
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