NTP has to be properly

alexneishell · ‎03-20-2014

Are there any recommendations, or things to look for, to correct udp jitter probes returning zero one way latency values? What are the determining factors for NTP to be out of spec for instance? Documentation on Cisco's site is very vague, curious to see how many others have encountered/fixed this type of issue. Here is what my probes typically show -

rtr-01#sh ip sla stat 2

IPSLAs Latest Operation Statistics

IPSLA operation id: 2

Type of operation: udp-jitter

Latest RTT: 1 milliseconds

Latest operation start time: 16:33:06 UTC Thu Mar 20 2014

Latest operation return code: OK

RTT Values:

Number Of RTT: 50 RTT Min/Avg/Max: 1/1/1 milliseconds

Latency one-way time:

Number of Latency one-way Samples: 0

Source to Destination Latency one way Min/Avg/Max: 0/0/0 milliseconds

Destination to Source Latency one way Min/Avg/Max: 0/0/0 milliseconds

Jitter Time:

Number of SD Jitter Samples: 49

Number of DS Jitter Samples: 49

Source to Destination Jitter Min/Avg/Max: 0/1/1 milliseconds

Destination to Source Jitter Min/Avg/Max: 0/286/1000 milliseconds

Over Threshold:

Number Of RTT Over Threshold: 0 (0%)

Packet Loss Values:

Loss Source to Destination: 0

Source to Destination Loss Periods Number: 0

Source to Destination Loss Period Length Min/Max: 0/0

Source to Destination Inter Loss Period Length Min/Max: 0/0

Loss Destination to Source: 0

Destination to Source Loss Periods Number: 0

Destination to Source Loss Period Length Min/Max: 0/0

Destination to Source Inter Loss Period Length Min/Max: 0/0

Out Of Sequence: 0 Tail Drop: 0

Packet Late Arrival: 0 Packet Skipped: 0

Voice Score Values:

Calculated Planning Impairment Factor (ICPIF): 1

MOS score: 4.34

Number of successes: 349

Number of failures: 0

Operation time to live: Forever

rtr-01#

rtr-01#sh ntp status

Clock is synchronized, stratum 3, reference is 127.127.1.1

nominal freq is 250.0000 Hz, actual freq is 249.9830 Hz, precision is 2**10

ntp uptime is 266584600 (1/100 of seconds), resolution is 4016

reference time is D6D59727.824DD458 (16:34:47.509 UTC Thu Mar 20 2014)

clock offset is 0.0000 msec, root delay is 0.00 msec

root dispersion is 2.25 msec, peer dispersion is 1.20 msec

loopfilter state is 'CTRL' (Normal Controlled Loop), drift is 0.000067971 s/s

system poll interval is 16, last update was 5 sec ago.

rtr-01#

Jakub Obetko · ‎04-14-2014

Is there any solution for this problem? I have exactly the same one - routers are synced with NTP server, i am in lab environment, NTP server is max 3 hops away from client using Ethernet connection. IP SLA probe is crossing max 5 hops. I am bothering with this quite a long time and found out nothing - the only thing that came to my mind after all that time is that problem might be in NTP server - which is actually one of Cisco routers.

alexneishell · ‎04-15-2014

Any chance you can do a debug on the probe? Just curious to see how similiar they are. I use a shadow router, and my ntp is synched with its neighbor. I ran debug ip sla trace and debug ip sla error and it returned the following -

pr 10 14:33:29.577: IPSLA-OPER_TRACE:OPER:618460002 Socket send jitter packet:64

Apr 10 14:33:29.593: IPSLA-OPER_TRACE:OPER:618460002 sourceSeq: 1, destSeq: 1

Apr 10 14:33:29.593: IPSLA-OPER_TRACE:OPER:618460002 ST: 3606129209.555791, RT: 4.103340, T3: 3606129209.576157, CT: 2.835765

Apr 10 14:33:29.593: IPSLA-OPER_TRACE:OPER:618460002 seq=0, rtt=1000

Apr 10 14:33:29.593: IPSLA-OPER_TRACE:OPER:618460002 udp-jitter, SeqNum verify passed:[srcSeq=1, destSeq =1]

Apr 10 14:33:29.593: IPSLA-OPER_TRACE:OPER:618460002 discarding ow values; one of the value could be negative

Apr 10 14:33:29.597: IPSLA-OPER_TRACE:OPER:618460002 Interval timer expire

Apr 10 14:33:29.597: IPSLA-OPER_TRACE:OPER:618460002 Socket send jitter packet:64

Apr 10 14:33:29.617: IPSLA-OPER_TRACE:OPER:618460002 Interval timer expire

Apr 10 14:33:29.617: IPSLA-OPER_TRACE:OPER:618460002 Socket send jitter packet:64

Apr 10 14:33:29.617: IPSLA-OPER_TRACE:OPER:618460002 sourceSeq: 2, destSeq: 2

Apr 10 14:33:29.617: IPSLA-OPER_TRACE:OPER:618460002 ST: 3606129209.577812, RT: 4.103340, T3: 3606129209.598894, CT: 2.835765

Apr 10 14:33:29.617: IPSLA-OPER_TRACE:OPER:618460002 seq=1, rtt=1000

Apr 10 14:33:29.617: IPSLA-OPER_TRACE:OPER:618460002 udp-jitter, SeqNum verify passed:[srcSeq=2, destSeq =2]

Apr 10 14:33:29.617: IPSLA-OPER_TRACE:OPER:618460002 discarding ow values; one of the value could be negative

Apr 10 14:33:29.617: IPSLA-OPER_TRACE:OPER:618460002 seq=1, jitterOut=22021, jitterIn=22737

Apr 10 14:33:29.637: IPSLA-OPER_TRACE:OPER:618460002 Interval timer expire

Apr 10 14:33:29.637: IPSLA-OPER_TRACE:OPER:618460002 Socket send jitter packet:64

Apr 10 14:33:29.637: IPSLA-OPER_TRACE:OPER:618460002 sourceSeq: 3, destSeq: 3

Apr 10 14:33:29.637: IPSLA-OPER_TRACE:OPER:618460002 ST: 3606129209.597747, RT: 4.103340, T3: 3606129209.617545, CT: 2.835765

Apr 10 14:33:29.637: IPSLA-OPER_TRACE:OPER:618460002 seq=2, rtt=1000

Apr 10 14:33:29.637: IPSLA-OPER_TRACE:OPER:618460002 udp-jitter, SeqNum verify passed:[srcSeq=3, destSeq =3]

Apr 10 14:33:29.637: IPSLA-OPER_TRACE:OPER:618460002 discarding ow values; one of the value could be negative

Apr 10 14:33:29.637: IPSLA-OPER_TRACE:OPER:618460002 seq=2, jitterOut=19935, jitterIn=18651

Apr 10 14:33:29.657: IPSLA-OPER_TRACE:OPER:618460002 Interval timer expire

Apr 10 14:33:29.657: IPSLA-OPER_TRACE:OPER:618460002 Socket send jitter packet:64

Apr 10 14:33:29.657: IPSLA-OPER_TRACE:OPER:618460002 sourceSeq: 4, destSeq: 4

Apr 10 14:33:29.657: IPSLA-OPER_TRACE:OPER:618460002 ST: 3606129209.618198, RT: 4.103340, T3: 3606129209.638366, CT: 2.835765

Apr 10 14:33:29.657: IPSLA-OPER_TRACE:OPER:618460002 seq=3, rtt=1000

Apr 10 14:33:29.657: IPSLA-OPER_TRACE:OPER:618460002 udp-jitter, SeqNum verify passed:[srcSeq=4, destSeq =4]

Apr 10 14:33:29.657: IPSLA-OPER_TRACE:OPER:618460002 discarding ow values; one of the value could be negative

Apr 10 14:33:29.657: IPSLA-OPER_TRACE:OPER:618460002 seq=3, jitterOut=20451, jitterIn=20821

Apr 10 14:33:29.677: IPSLA-OPER_TRACE:OPER:618460002 Interval timer expire

Apr 10 14:33:29.677: IPSLA-OPER_TRACE:OPER:618460002 Socket send jitter packet:64

Apr 10 14:33:29.677: IPSLA-OPER_TRACE:OPER:618460002 sourceSeq: 5, destSeq: 5

Apr 10 14:33:29.677: IPSLA-OPER_TRACE:OPER:618460002 ST: 3606129209.637832, RT: 4.103340, T3: 3606129209.658200, CT: 2.835765

Apr 10 14:33:29.677: IPSLA-OPER_TRACE:OPER:618460002 seq=4, rtt=1000

Apr 10 14:33:29.677: IPSLA-OPER_TRACE:OPER:618460002 udp-jitter, SeqNum verify passed:[srcSeq=5, destSeq =5]

Apr 10 14:33:29.677: IPSLA-OPER_TRACE:OPER:618460002 discarding ow values; one of the value could be negative

Apr 10 14:33:29.677: IPSLA-OPER_TRACE:OPER:618460002 seq=4, jitterOut=19634, jitterIn=19834

Apr 10 14:33:29.697: IPSLA-OPER_TRACE:OPER:618460002 Interval timer expire

Apr 10 14:33:29.697: IPSLA-OPER_TRACE:OPER:618460002 Socket send jitter packet:64

Apr 10 14:33:29.697: IPSLA-OPER_TRACE:OPER:618460002 sourceSeq: 6, destSeq: 6

Apr 10 14:33:29.697: IPSLA-OPER_TRACE:OPER:618460002 ST: 3606129209.657787, RT: 4.103340, T3: 3606129209.677544, CT: 2.835765

Apr 10 14:33:29.697: IPSLA-OPER_TRACE:OPER:618460002 seq=5, rtt=1000

Apr 10 14:33:29.697: IPSLA-OPER_TRACE:OPER:618460002 udp-jitter, SeqNum verify passed:[srcSeq=6, destSeq =6]

Apr 10 14:33:29.697: IPSLA-OPER_TRACE:OPER:618460002 discarding ow values; one of the value could be negative

Apr 10 14:33:29.697: IPSLA-OPER_TRACE:OPER:618460002 seq=5, jitterOut=19955, jitterIn=19344

Apr 10 14:33:29.717: IPSLA-OPER_TRACE:OPER:618460002 Interval timer expire

Apr 10 14:33:29.717: IPSLA-OPER_TRACE:OPER:618460002 Socket send jitter packet:64

Apr 10 14:33:29.717: IPSLA-OPER_TRACE:OPER:618460002 sourceSeq: 7, destSeq: 7

Apr 10 14:33:29.717: IPSLA-OPER_TRACE:OPER:618460002 ST: 3606129209.677777, RT: 4.103340, T3: 3606129209.698724, CT: 2.835765

Apr 10 14:33:29.717: IPSLA-OPER_TRACE:OPER:618460002 seq=6, rtt=1000

Apr 10 14:33:29.717: IPSLA-OPER_TRACE:OPER:618460002 udp-jitter, SeqNum verify passed:[srcSeq=7, destSeq =7]

Apr 10 14:33:29.717: IPSLA-OPER_TRACE:OPER:618460002 discarding ow values; one of the value could be negative

Apr 10 14:33:29.717: IPSLA-OPER_TRACE:OPER:618460002 seq=6, jitterOut=19990, jitterIn=21180

Apr 10 14:33:29.737: IPSLA-OPER_TRACE:OPER:618460002 Interval timer expire

Apr 10 14:33:29.737: IPSLA-OPER_TRACE:OPER:618460002 Socket send jitter packet:64

Apr 10 14:33:29.737: IPSLA-OPER_TRACE:OPER:618460002 sourceSeq: 8, destSeq: 8

Apr 10 14:33:29.737: IPSLA-OPER_TRACE:OPER:618460002 ST: 3606129209.698292, RT: 4.103340, T3: 3606129209.718318, CT: 2.835765

Apr 10 14:33:29.737: IPSLA-OPER_TRACE:OPER:618460002 seq=7, rtt=1000

Apr 10 14:33:29.737: IPSLA-OPER_TRACE:OPER:618460002 udp-jitter, SeqNum verify passed:[srcSeq=8, destSeq =8]

Apr 10 14:33:29.737: IPSLA-OPER_TRACE:OPER:618460002 discarding ow values; one of the value could be negative

Apr 10 14:33:29.737: IPSLA-OPER_TRACE:OPER:618460002 seq=7, jitterOut=20515, jitterIn=19594

Apr 10 14:33:29.757: IPSLA-OPER_TRACE:OPER:618460002 Interval timer expire

Apr 10 14:33:29.757: IPSLA-OPER_TRACE:OPER:618460002 sourceSeq: 9, destSeq: 9

Apr 10 14:33:29.757: IPSLA-OPER_TRACE:OPER:618460002 ST: 3606129209.717799, RT: 4.103340, T3: 3606129209.737651, CT: 2.835765

Apr 10 14:33:29.757: IPSLA-OPER_TRACE:OPER:618460002 seq=8, rtt=1000

Apr 10 14:33:29.757: IPSLA-OPER_TRACE:OPER:618460002 udp-jitter, SeqNum verify passed:[srcSeq=9, destSeq =9]

Apr 10 14:33:29.757: IPSLA-OPER_TRACE:OPER:618460002 discarding ow values; one of the value could be negative

Apr 10 14:33:29.757: IPSLA-OPER_TRACE:OPER:618460002 seq=8, jitterOut=19507, jitterIn=19333

Apr 10 14:33:29.777: IPSLA-OPER_TRACE:OPER:618460002 sourceSeq: 10, destSeq: 10

Apr 10 14:33:29.777: IPSLA-OPER_TRACE:OPER:618460002 ST: 3606129209.737808, RT: 4.103340, T3: 3606129209.757691, CT: 2.835765

Apr 10 14:33:29.777: IPSLA-OPER_TRACE:OPER:618460002 seq=9, rtt=1000

Apr 10 14:33:29.777: IPSLA-OPER_TRACE:OPER:618460002 udp-jitter, SeqNum verify passed:[srcSeq=10, destSeq =10]

Apr 10 14:33:29.777: IPSLA-OPER_TRACE:OPER:618460002 discarding ow values; one of the value could be negative

Apr 10 14:33:29.777: IPSLA-OPER_TRACE:OPER:618460002 seq=9, jitterOut=20009, jitterIn=20040

Apr 10 14:33:29.777: IPSLA-INFRA_TRACE:OPER:618460002 Updating result

ivanrengo · ‎09-08-2014

Hi. I'm seeing that you have an strange value of DS jitter

Jitter Time:

Number of SD Jitter Samples: 49

Number of DS Jitter Samples: 49

Source to Destination Jitter Min/Avg/Max: 0/1/1 milliseconds

Destination to Source Jitter Min/Avg/Max: 0/286/1000 milliseconds

I'm having a similar scenario and I'm trying to figure it out if this jitter value have anything to do with the problem.

Jakub Obetko · ‎09-08-2014

Well, it did not. I have found out that the problem was in time synchronization. If you want to measure one way delay, NTP has to be set up to synchronize clock between routers (jitter can work without it). The more accurately you want to measure delay, the more accurate has the sync be. If you set up NTP and wait till it will sync (i set it up to send updates as frequent as possible) then one way delay will be measured. If the clock drift between routers is 2ms, you will have measuring precision 2-3 ms.

alexneishell · ‎09-08-2014

I have found that NTP synch AND using millisecond measurements will give you one way measurements. Why? Not exactly sure, but those have been my observations. I changed from microseconds to milli and began to see one way stats

Jakub Obetko · ‎09-09-2014

That is because the way one way delay is measured. You can check on cisco sites (i do not have nay link right now) and you will understand why the clocks has to be in precise sync in order to calculate any values for one way delay. Millisecond precision helped as the clock require only ms precision in sync, microsecond is impossible with NTP i think.

farquleet · ‎08-09-2015

HI Alex

Seems I have the same issue. When you say "using millisecond measurement" what exactly does it mean? Does it relate to NTP configuration or the IP SLA configuration?

Following is the output that I am getting.

IPSLA operation id: 400
Type of operation: udp-jitter
Latest RTT: 1 milliseconds
Latest operation start time: 06:03:10 UTC Sun Aug 9 2015
Latest operation return code: OK
Over thresholds occurred: FALSE
RTT Values:
Number Of RTT: 200 RTT Min/Avg/Max: 1/1/10 milliseconds
Latency one-way time:
Number of Latency one-way Samples: 0
Source to Destination Latency one way Min/Avg/Max: 0/0/0 milliseconds
Destination to Source Latency one way Min/Avg/Max: 0/0/0 milliseconds
Source to Destination Latency one way Sum/Sum2: 0/0
Destination to Source Latency one way Sum/Sum2: 0/0
Jitter Time:
Number of SD Jitter Samples: 199
Number of DS Jitter Samples: 199
Source to Destination Jitter Min/Avg/Max: 3/67/983 milliseconds
Destination to Source Jitter Min/Avg/Max: 0/1/3 milliseconds
Source to destination positive jitter Min/Avg/Max: 902/952/983 milliseconds
Source to destination positive jitter Number/Sum/Sum2: 7/6668/6358044
Source to destination negative jitter Min/Avg/Max: 3/33/502 milliseconds
Source to destination negative jitter Number/Sum/Sum2: 192/6516/545438
Destination to Source positive jitter Min/Avg/Max: 1/1/3 milliseconds
Destination to Source positive jitter Number/Sum/Sum2: 59/69/91
Destination to Source negative jitter Min/Avg/Max: 1/1/3 milliseconds
Destination to Source negative jitter Number/Sum/Sum2: 56/68/94
Interarrival jitterout: 0 Interarrival jitterin: 0
Jitter AVG: 34
Packet Loss Values:
Loss Source to Destination: 0
Source to Destination Loss Periods Number: 0
Source to Destination Loss Period Length Min/Max: 0/0
Source to Destination Inter Loss Period Length Min/Max: 0/0
Loss Destination to Source: 0
Destination to Source Loss Periods Number: 0
Destination to Source Loss Period Length Min/Max: 0/0
Destination to Source Inter Loss Period Length Min/Max: 0/0
Out Of Sequence: 0 Tail Drop: 0 Packet Late Arrival: 0
Packet Skipped: 0
Voice Score Values:
Calculated Planning Impairment Factor (ICPIF): 0
Mean Opinion Score (MOS): 0
Number of successes: 3
Number of failures: 0
Operation time to live: Forever
Operational state of entry: Active
Last time this entry was reset: Never

Kind Regards

Ahmad

Regards Mian Ahmad

alexneishell · ‎08-09-2015

NTP has to be properly working to get one-way stats, and it reports in milliseconds. Milliseconds is the default measurement. If you choose to configure microsecond measurements one-way stats are not calculated. Hope that helps

farquleet · ‎08-09-2015

Thanks Alex,

Really appreciate your help. My IP SLAs are using the default millisecond reporting, and the devices are also synced with NTP. but still the same issue. And not just that the one way jitter values also seem very unreal. The maximum RTT is 10 ms while the jitter seems to be as high as 900 ms.

Thanks and Regards

Mian Ahmad

Regards Mian Ahmad

alexneishell · ‎08-10-2015

RTT values that are that far off are sometimes the result of an IOS bug, you should definitely check into that. Also, the probe sender and responder need to be synced with the same NTP master in order for one way RTT to work.

IP SLA udp-jitter and Latency one-way time = 0