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Does drops on queueing affect IP SLA icmp-echo?

Lost & Found
Explorer
Explorer

Hi All,

Is there any possibility that that drops on output queue affects the IP SLA probe when sending icmp-echo? Drop is randomly happening and when I ping point-to-point I'm not able to detect any drops.

LOGS:
05:00:20.847: %TRACK-6-STATE: 11 ip sla 11 reachability Up -> Down
05:00:20.847: %TRACK-6-STATE: 21 ip sla 21 reachability Up -> Down
05:00:20.847: %TRACK-6-STATE: 31 ip sla 31 reachability Up -> Down
05:00:55.899: %TRACK-6-STATE: 21 ip sla 21 reachability Down -> Up
05:01:00.899: %TRACK-6-STATE: 11 ip sla 11 reachability Down -> Up
05:01:00.899: %TRACK-6-STATE: 31 ip sla 31 reachability Down -> Up
06:38:26.360: %TRACK-6-STATE: 11 ip sla 11 reachability Up -> Down
06:38:26.360: %TRACK-6-STATE: 21 ip sla 21 reachability Up -> Down
06:38:26.360: %TRACK-6-STATE: 31 ip sla 31 reachability Up -> Down
06:39:06.408: %TRACK-6-STATE: 11 ip sla 11 reachability Down -> Up
06:39:06.408: %TRACK-6-STATE: 21 ip sla 21 reachability Down -> Up
06:39:06.408: %TRACK-6-STATE: 31 ip sla 31 reachability Down -> Up

11     ip sla      11                          reachability     Up    00:48:28
21     ip sla      21                          reachability     Up    00:48:28
31     ip sla      31                          reachability     Up    00:48:28

#ping 10.1.2.1 source 10.1.2.2 repeat 5000 size 1500 df-bit 
(cut)
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (5000/5000), round-trip min/avg/max = 1/2/32 ms

#sh policy-map int g0/1                                                 
 GigabitEthernet0/1 
  Service-policy output: etm-GrupoSalinas-Elektra-lima
    Class-map: class-default (match-any)  
      261661475791 packets, 146841546500637 bytes
      30 second offered rate 11024000 bps, drop rate 0000 bps
      Match: any 
      Queueing
      queue limit 4096 packets
      (queue depth/total drops/no-buffer drops) 0/1011428/0    <--- not inc. as of now
      (pkts output/bytes output) 261660459030/152073955468691
      shape (average) cir 30000000, bc 140000, be 0
      target shape rate 30000000
       Overhead Accounting Enabled

No Congestion at the time that the total drop increased.. Could be bursty traffic..

Here's the QOS policy:

Router in question:
policy-map parent-policy
 class class-default
  shape average 30000000 140000 0 account user-defined 20
  queue-limit 4096 packets

From other site, Nested QOS is being implemented. Should I replicate this on this site and this purpose of this child policy is prioritize the traffic and smoothen the connection?

Working site:
policy-map parent-policy
 class class-default
  shape average 150000000 600000 0 
   service-policy child-policy <-- Child
!
policy-map child-policy
 class realtime
  priority
 class priority
  bandwidth remaining percent 40 
  random-detect dscp-based
 class missioncritical
  bandwidth remaining percent 39 
  random-detect dscp-based
 class transactional
  bandwidth remaining percent 16 
  random-detect dscp-based
 class general
  bandwidth remaining percent 1 
  random-detect dscp-based
 class class-default
  bandwidth remaining percent 4 
  random-detect dscp-based

10     ip sla      10                          reachability     Up    1w2d <- Stable

Thank you

6 Replies 6

balaji.bandi
VIP Community Legend VIP Community Legend
VIP Community Legend

depends on where the QOS policy is applied, are you using the same interface to IP SLA as source?

 

 

BB

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@balaji.bandi , Yes, source interface of IP SLA is the one with QOS drops. 

Just to make it clear to understand the issue remove the QoS for testing, what was the outcome ?

 

BB

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@balaji.bandi , 

That I need to check. BTW, the values that I'm using still acceptable? 

ip sla 1
icmp-echo x.x.x.x source-interface x/y
threshold 1000
timeout 2000
frequency 3

 

 

Joseph W. Doherty
Hall of Fame Master Hall of Fame Master
Hall of Fame Master

"Is there any possibility that that drops on output queue affects the IP SLA probe when sending icmp-echo?"

Sure, but often the idea behind SLA is to "see" issues happening to your normal/production traffic too.

"Drop is randomly happening and when I ping point-to-point I'm not able to detect any drops."

The "random" part is likely why you don't catch it with your manual ping tests, another purpose of SLA is to catch "random", or more likely occasionally, issues.  Also, is it possible SLA drops are not on interface, but further downstream and/or on return path?

"From other site, Nested QOS is being implemented. Should I replicate this on this site and this purpose of this child policy is prioritize the traffic and smoothen the connection?"

Depends on your QoS policy you wish to support.  The policy with the child policy does prioritize kinds of traffic, differently.  As to "smoothen", not so much that policy, except for some of the higher prioritized classes.  Even then, WRED, can be quirky.  I generally recommend against using it unless you're a QoS expert, as WRED isn't as simplistic as its usual documentation would lead you to believe.

Georg Pauwen
VIP Master VIP Master
VIP Master

Hello,

 

just to be sure (and I hope I am reading this correctly): you are shaping 30Mbps on a GigabitEthernet link ? 30 Mbps seems low, by today's standards...

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