What is the meaning of different values in " ntpq> rv assID " output ?

Solution Verified - Updated

Environment

  • Red Hat Enterprise Linux 5

  • Red Hat Enterprise Linux 6

Issue

  • How to interpret ntpq> rv assocID output to check if NTP is synchronizing correctly or not ?

Resolution

ntpq> rv 29583
assID=62236 status=9014 reach, conf, 1 event, event_reach,
srcadr=192.168.23.1, srcport=123, dstadr=192.168.247.11, dstport=123,
leap=00, stratum=3, precision=-6, rootdelay=218.750,
rootdispersion=1381.516, refid=24.1.4.14, reach=377, unreach=0,
hmode=3, pmode=4, hpoll=10, ppoll=10, flash=400 peer_dist, keyid=0,
ttl=0, offset=-29.750, delay=0.316, dispersion=30.400, jitter=1.136,
reftime=d1e4505b.d456f5b0  Thu, Aug  4 2011  0:55:23.829,
org=d1e4c793.e477ba4b  Thu, Aug  4 2011  9:24:03.892,
rec=d1e4c793.ec1fc3ac  Thu, Aug  4 2011  9:24:03.922,
xmt=d1e4c793.ec0b133c  Thu, Aug  4 2011  9:24:03.922,
filtdelay=     0.32    0.40    0.33    0.45    0.42    0.42    0.33    0.38,
filtoffset=  -29.75  -30.89  -29.97  -30.11  -30.15  -29.20  -30.25  -30.36,
filtdisp=     15.63   31.00   46.38   61.75   77.14   92.52  107.91  123.28

  • The rv command displays the system variables billboard, including the system status word.

  • The rv assocID command, where assocID is the association ID, displays the peer variables billboard, including the peer status word. Note that, except for explicit calendar dates, times are in milliseconds and frequencies are in parts-per-million (PPM).

  • The server has successfully synchronized to its sources if the leap peer variable has value other than 3 (11b). The client has successfully synchronized to the server when the leap system variable has value other than 3.

  • The reach peer variable is an 8-bit shift register displayed in octal format. When a valid packet is received, the rightmost bit is lit. When a packet is sent, the register is shifted left one bit with 0 replacing the rightmost bit. If the reach value is nonzero, the server is reachable; otherwise, it is unreachable. Note that, even if all servers become unreachable, the system continues to show valid time to dependent applications.

  • A useful indicator of miscellaneous problems is the flash peer variable, which shows the result of Content from www.eecis.udel.edu is not included.13 sanity tests. It contains the flash status word bits, commonly called flashers, which displays the current errors for the association. These bits should be zero for a valid server.

  • The flash codes in the rv command output give the reason why the ntp source is rejected:

flash=400 peer_dist
    distance threshold exceeded

flash=800 peer_loop
    peer synchronization loop

  • Refer this article for details on flash codes.

  • The three peer variables filtdelay filtoffset and filtdisp show the delay offset and jitter statistics for each of the last eight measurement rounds. These statistics and their trends are valuable performance indicators for the server, client and the network.

  • For instance, large fluctuations in delay and jitter suggest network congestion. Missing clock filter stages suggest packet losses in the network.

  • The synchronization distance, defined as one-half the delay plus the dispersion, represents the maximum error statistic.

  • The jitter represents the expected error statistic.

  • The maximum error and expected error calculated from the peer variables represents the quality metric for the server.

  • The maximum error and expected error calculated from the system variables represents the quality metric for the client.

  • If the root synchronization distance for any server exceeds 1.5 s, called the select threshold, the server is considered invalid.

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