Hello,
We are observing a change in behavior of the mls qos on the 2960 switch series between IOS 15.2.(4)E6 and 15.2.(7)E5.
The applied configuration is as follows:
mls qos map cos-dscp 0 0 0 0 0 0 0 0
mls qos map dscp-cos 0 1 2 3 4 5 6 7 to 0
mls qos map dscp-cos 8 9 10 11 12 13 14 15 to 0
mls qos map dscp-cos 16 17 18 19 20 21 22 23 to 0
mls qos map dscp-cos 24 25 26 27 28 29 30 31 to 0
mls qos map dscp-cos 32 33 34 35 36 37 38 39 to 0
mls qos map dscp-cos 40 41 42 43 44 45 46 47 to 0
mls qos map dscp-cos 48 49 50 51 52 53 54 55 to 0
mls qos map dscp-cos 56 57 58 59 60 61 62 63 to 0
mls qos srr-queue output cos-map queue 3 threshold 3 0 1 2 3 4 5 6 7
mls qos srr-queue output cos-map queue 2 threshold 3 6
mls qos srr-queue output dscp-map queue 3 threshold 3 0 1 2 3 4 5 6 7
mls qos srr-queue output dscp-map queue 3 threshold 3 8 9 10 11 12 13 14 15
mls qos srr-queue output dscp-map queue 3 threshold 3 16 17 18 19 20 21 22 23
mls qos srr-queue output dscp-map queue 3 threshold 3 24 25 26 27 28 29 30 31
mls qos srr-queue output dscp-map queue 3 threshold 3 32 33 34 35 36 37 38 39
mls qos srr-queue output dscp-map queue 3 threshold 3 40 41 42 43 44 45 46 47
mls qos srr-queue output dscp-map queue 3 threshold 3 48 49 50 51 52 53 54 55
mls qos srr-queue output dscp-map queue 3 threshold 3 56 57 58 59 60 61 62 63
mls qos srr-queue output dscp-map queue 2 threshold 3 48 56
mls qos srr-queue output dscp-map queue 1 threshold 3 40 42 46
mls qos queue-set output 1 buffers 50 25 25 0
no mls qos rewrite ip dscp
interface range GigabitEthernet 0/1 - 6
description "## Unused Rac. ##"
switchport access vlan 2
switchport mode access
switchport nonegotiate
no flowcontrol receive off
mls qos cos 0
no mls qos cos override
mls qos trust dscp
priority-queue out
srr-queue bandwidth share 1 1 1 1
spanning-tree portfast edge
shutdown
!
We inject traffic, approximately 600Mb, via an IXIA chassis with several flows with packets of different sizes 80 bytes, 250 bytes, 750 bytes, of type UDP and TCP with different markings EF, CS4, CS5, BestEffort.
The mls qos drops in output on threshold 3 but only a few packets (20/70000000).
Increasing the drop trigger thresholds does not change this behavior.
Do you have any idea to mitigate these mls drops?
Would upgrading with the latest version of IOS 15.2.(7)E9 resolve this problem?
