IP-sla udp-jitter / one-way delay no output

Unanswered Question
Jan 12th, 2010

Hi *,

i have a question regarding "ip sla udp-jitter".
On some connectins i get an output for the "show ip sla stat" for the _one-way delay_
on other links i don't get an output. The Configuration is always the same and the Probes are running.
NTP is configured but in my opinion the fact weather i get output for the _one-way delay_
or not depends on the ntp root despersion.
Is there a max allowed time differances between the two routes ?

Here one working / one not working output of the same Router but different peers:

Not working::

Latest operation return code: OK

RTT Values:

Number Of RTT: 100RTT Min/Avg/Max: 11/11/13 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

----------------------------------------------------------------------------------------------------------------

Working:

Latest operation return code: OK

RTT Values:

Number Of RTT: 100RTT Min/Avg/Max: 12/13/14 milliseconds

Latency one-way time:

Number of Latency one-way Samples: 100

Source to Destination Latency one way Min/Avg/Max: 6/7/8 milliseconds

Destination to Source Latency one way Min/Avg/Max: 5/6/7 milliseconds

I hope one of you can help me to find / fix the problem,

Thanks in advance / Emanuel

I have this problem too.
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khernandezruiz Wed, 10/27/2010 - 09:05

Hi everyone,

I have the same doubt.

I did a ip sla configuration on 1841 and 7206VXR and don't show nothing in one-way delay.

----------------------7206---------------------

-ip sla monitor responder
-ip sla monitor 1
- type jitter dest-ipaddr 10.9.105.14 dest-port 16384 source-ipaddr 10.8.20.102  codec g711alaw
- tos 184
-ip sla monitor schedule 1 start-time now
-ntp peer 10.9.105.14

HOST)#show ip sla sta

Round Trip Time (RTT) for       Index 1
        Latest RTT: 507 milliseconds
Latest operation start time: 10:57:36.619 UTC Sun Oct 10 2010
Latest operation return code: OK
RTT Values:
        Number Of RTT: 1000             RTT Min/Avg/Max: 125/507/846 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 Jitter Samples: 999
        Source to Destination Jitter Min/Avg/Max: 1/1/6 milliseconds
        Destination to Source Jitter Min/Avg/Max: 1/5/23 milliseconds
Packet Loss Values:
        Loss Source to Destination: 0           Loss Destination to Source: 0
        Out Of Sequence: 0      Tail Drop: 0    Packet Late Arrival: 0
Voice Score Values:
        Calculated Planning Impairment Factor (ICPIF): 17
        Mean Opinion Score (MOS): 3.84
Number of successes: 38
Number of failures: 0
Operation time to live: 1347 sec

-------------------------1841-------------------------------

-ip sla monitor responder
-ip sla monitor 1
- type jitter dest-ipaddr 10.8.20.102 dest-port 16384 source-ipaddr 10.9.105.14 codec g711alaw
- tos 184
-ip sla monitor schedule 1 start-time now
-ntp peer 10.8.20.102

3383)#show ip sla monitor statistic
Round trip time (RTT)   Index 1
        Latest RTT: 614 ms
Latest operation start time: 10:50:50.491 UTC Wed Oct 27 2010
Latest operation return code: OK
RTT Values
        Number Of RTT: 999
        RTT Min/Avg/Max: 347/614/867 ms
Latency one-way time milliseconds
        Number of one-way Samples: 0
        Source to Destination one way Min/Avg/Max: 0/0/0 ms
        Destination to Source one way Min/Avg/Max: 0/0/0 ms
Jitter time milliseconds
        Number of SD Jitter Samples: 997
        Number of DS Jitter Samples: 998
        Source to Destination Jitter Min/Avg/Max: 0/6/19 ms
        Destination to Source Jitter Min/Avg/Max: 0/1/3 ms
Packet Loss Values
        Loss Source to Destination: 1           Loss Destination to Source: 0
        Out Of Sequence: 0      Tail Drop: 0    Packet Late Arrival: 0
Voice Score Values
        Calculated Planning Impairment Factor (ICPIF): 20
MOS score: 3.72
Number of successes: 32
Number of failures: 0
Operation time to live: 1668 sec

ccarring Wed, 10/27/2010 - 09:47

Hi Emanuel,

I think the most likely cause here is that the NTP clocks on *some* of your responders are out of sync by more than 15% (of the latency measure in that packet) compared to the source router.

Enable debug for ip sla trace, and check the log for messages similar to the following:

029474: Aug 11 13:09:29.829 CDT: IPSLA-OPER_TRACE:OPER:1 icmp-jitter STS:65369798, RTD: 65369759, STD: 65369760, RTS: 65369831

The value from STS, RTD, STD and RTS should be in ascending order:    STS < RTD < STD < RTS.

In my example there, the log shows RTD is smaller than STS. Unfortunately, with  icmp-jitter, you can only try to bring Responder back in sync.

If you cannot bring time in sync between 2 devices, then alternatively, you might try to use udp-jitter which allows you to configure clock-tolerance.
Here's an example:

rt1(config-ip-sla)#udp-jitter 2.2.2.2 222

rt1(config-ip-sla-jitter)#clock-tolerance ntp oneway percent ?

  <0-100>  Percent of value measured

Can you use udp-jitter, or configure the clocks to bring them closer to sync?

Curtis

Jakub Obetko Sat, 04/26/2014 - 11:30

This solution does not work. When i configure clock-tolerance to any number it is still the same result: Number of latency samples = 0. And about the second solution - how am i supposed to bring 2 routers closer to sync when they are connected directly with ethernet cable one is NTP server and second is client?

tyoung008 Mon, 05/12/2014 - 12:12

If the routers are directly connected, IP SLA could be rounding the values to 0 if the OW delay is < .5 ms.

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