06-03-2008 01:04 AM
Hello.
We have a ME-3400 with IOS Metro IP.
The giga0/1 and gi0/3 ports are configured all the same with qos policing (input policy-map) and port shaping+Class Based Priority queueing (output policy-map).
We have no drop on gi0/1 output.
On gi0/3 output the drop is about 1-2% although the traffic (for example 10Mbps) is much less than the port shaped bandwidth (for example 200Mbps).
Can anyone help me?
Thank you.
06-03-2008 04:08 AM
Hello, sure we can.
1. Check the output policy map using "show policy-map interface gi 0/3 output" command. This should say exactly where packets are dropped.
2. Check the parameters. In the output the first line should say the following:
Service-policy output: XYZ
Class-map: class-default (match-any)
8645541 packets
Match: any
Traffic Shaping
Average Rate Traffic Shaping
CIR 11111120 (bps)
Output Queue:
Max queue-limit default threshold: 48
Tail Packets Drop: 0
Service-policy : ABC
Class-map: core-queue1 (match-any)
3321747 packets
Match: cos 5
Priority
police cir 1000000 bc 31250
conform-action transmit
exceed-action drop
conform: 0 (packets) exceed: 0 (packets)
Output Queue:
Max queue-limit default threshold: 48
Tail Packets Drop: 0
The bold values are critical - low buffers means high drop probability.
Remember - interface never sends data at any other rate than it's physical rate, meaning "LOAD" is just an average of how many bytes transferred over what time.
So if 1000 packets will arrive in one milisecond, and then you have no traffic for 10 seconds, average will be low load, but 1000 packets will not fit in 48 buffers and 952 packets will be dropped.
Increase buffers! use the following guideline: calculate how many packets can be sent in 10ms window, and increase the buffers accordingly. E.G for 100Mbps 1 Mb can be sent in 10ms, which is 1Mbps/8 = 125000 BYTES. With "packet" size of 250 (buffers are per packet but their size is limited) that's 500 buffer places, or 500 packets buffer.
3. Always pay attention to BC and TC values
Bursts will definitely be your problem
06-03-2008 04:27 AM
Hello "slidersv" and thank you 4 your attention.
I agree with you about BC and TC values, but it seems the buffer size (queue drop threshold) for the class-default in parent policy-map cannot be increased.
How can I modify the queue drop threshold - or the BC and TC values - in Policy-map PARENT-OUT ?
Thx.
This is our configuration:
policy-map PARENT-OUT
class class-default
shape average 200000000
service-policy CHILD-OUT
policy-map CHILD-OUT
class GOLD
police cir 4000000
priority
class class-default
queue-limit 272
And this is the "show policy-map" command with drops:
Service-policy output: PARENT-OUT
Class-map: class-default (match-any)
69129893 packets
Match: any
Traffic Shaping
Average Rate Traffic Shaping
CIR 200000000 (bps)
Output Queue:
Max queue-limit default threshold: 48
Tail Packets Drop: 953573
Service-policy : CHILD-OUT
Class-map: GOLD (match-any)
9668289 packets
Match: ip dscp ef (46)
police cir 4000000 bc 125000
conform-action transmit
exceed-action drop
conform: 9669394 (packets) exceed: 0 (packets)
Priority
Output Queue:
Max queue-limit default threshold: 48
Tail Packets Drop: 0
Class-map: class-default (match-any)
54789505 packets
Match: any
Tail Packets Drop: 953573
Queue Limit
queue-limit 272 (packets)
Output Queue:
Max queue-limit default threshold: 272
Tail Packets Drop: 953573
06-03-2008 05:47 AM
Hello.
Try setting queue-limit under every class-map, not on interface:
e.g.
policy-map child-out
class class-default
queue-limit 500
Hope this helps
06-03-2008 05:55 AM
Hi.
I try this:
policy-map CHILD-OUT
class GOLD
police cir 4000000
priority
class class-default
queue-limit 544
No improvement.
Sorry.
:-((
06-04-2008 10:51 PM
And I presume that "show interface gi0/3" output does not show any errors? What is the total load of Gigabit?
06-04-2008 10:55 PM
Exactly, no errors on gi0/3.
The load is about 6/255.
:-((
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