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karobar
Asked: 2018-01-12 07:34:53 +0800 CST

What does an 8 indicate in the Select Field of NTP Peer status?

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I've done ntpq, then ran associations and received the following:

ind assid status  conf reach auth condition  last_event cnt
===========================================================
  1 12097  c811   yes  none   yes    reject    mobilize  1

From the documentation from man ntp-decode (Peer Status), I've learned that the first digit indicates Status, the second Select, the third Count, and the fourth Code.

I've tried to find the Select Status section of this manual and found the following:

The Select Field displays the current selection status. (The T Field in the following table gives the corresponding tally codes used in the ntpq peers dis-
play.) The values are coded as follows:

+-------------------------+---------------------------------------+--------------------------+-------------------------------------------------------------+
|        Code             |            Message                    |            T             |            Description                                      |
+-------------------------+---------------------------------------+--------------------------+-------------------------------------------------------------+
|        0                |            sel_reject                 |                          |            discarded as not valid (TEST10-TEST13)           |
+-------------------------+---------------------------------------+--------------------------+-------------------------------------------------------------+
|        1                |            sel_falsetick              |            x             |            discarded by intersection algorithm              |
+-------------------------+---------------------------------------+--------------------------+-------------------------------------------------------------+
|        2                |            sel_excess                 |            .             |            discarded by table overflow (not used)           |
+-------------------------+---------------------------------------+--------------------------+-------------------------------------------------------------+
|        3                |            sel_outlyer                |            -             |            discarded by the cluster algorithm               |
+-------------------------+---------------------------------------+--------------------------+-------------------------------------------------------------+
|        4                |            sel_candidate              |            +             |            included by the combine algorithm                |
+-------------------------+---------------------------------------+--------------------------+-------------------------------------------------------------+
|        5                |            sel_backup                 |            #             |            backup (more than tos maxclock sources)          |
+-------------------------+---------------------------------------+--------------------------+-------------------------------------------------------------+
|        6                |            sel_sys.peer               |            *             |            system peer                                      |
+-------------------------+---------------------------------------+--------------------------+-------------------------------------------------------------+
|        7                |            sel_pps.peer               |            o             |            PPS peer (when the prefer peer is valid)         |
+-------------------------+---------------------------------------+--------------------------+-------------------------------------------------------------+

So, what does the 8 digit for Select Status mean?

ntp

1 Answers

  1. Best Answer

    The explanation of peer status codes in the docs says that the status field "is 5 bits wide, and combines with the the 3-bit-wide Select Field to create the first full byte of the peer status word." The select field is 3 bits, so it can only have the values 0-7. The 8 in the 2nd digit is the least-significant bit in the status field, not the most-significant bit in the select field.

    So c8 means "persistent association", "authentication enabled", and "broadcast association" (bits 0, 1, and 4, counting big-endian). You can get ntpq to interpret these fields for you by using the readvar command. Here's an example from my laptop, which is configured to use [0-3].ubuntu.pool.ntp.org in pool mode:

    # ntpq -n
ntpq> peers
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 0.ubuntu.pool.n .POOL.          16 p    -   64    0    0.000    0.000   0.000
 1.ubuntu.pool.n .POOL.          16 p    -   64    0    0.000    0.000   0.000
...
ntpq> assoc

ind assid status  conf reach auth condition  last_event cnt
===========================================================
  1 32962  8811   yes  none  none    reject    mobilize  1
  2 32963  8811   yes  none  none    reject    mobilize  1
...
ntpq> readvar 32962
associd=32962 status=8811 conf, bcast, sel_reject, 1 event, mobilize,
srcadr=0.0.0.0, srcport=0, srchost="0.ubuntu.pool.ntp.org",
dstadr=0.0.0.0, dstport=0, leap=11, stratum=16, precision=-24,
rootdelay=0.000, rootdisp=0.000, refid=POOL,
reftime=00000000.00000000  Thu, Feb  7 2036 16:28:16.000,
...

    Note the "conf" (permanently-configured association) and "bcast" (broadcast association), which are short interpretations of the status field. (Apparently broadcast can mean more than just broadcast when it has a refid of POOL.)

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