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Layer 2 QoS Congestion management - Help

Andres Franco
Level 1
Level 1

Hello everyone.

I´ve an escenario with some cisco access switches and cisco router that support connectivity for IP telephony. But the PBX is Nortel. Suppose i am trying to manage voice and signaling traffic with the recommended values (CoS5 and CoS3), and that i´m changing DSCP values on access port so i can use DSCP 24 for signaling and DSCP 46 for voice (not trusting DSCP but remarking with a policy MAP). Then on switches i´ve the following congestion managemente config:

mls qos srr-queue output cos-map queue 1 threshold 3 5

mls qos srr-queue output cos-map queue 2 threshold 1 2 4

mls qos srr-queue output cos-map queue 2 threshold 2 3

mls qos srr-queue output cos-map queue 2 threshold 3 6 7

mls qos srr-queue output cos-map queue 3 threshold 3 0

mls qos srr-queue output cos-map queue 4 threshold 3 1

mls qos srr-queue output dscp-map queue 1 threshold 3 46

mls qos srr-queue output dscp-map queue 2 threshold 1 16

mls qos srr-queue output dscp-map queue 2 threshold 1 18 20 22

mls qos srr-queue output dscp-map queue 2 threshold 1 25

mls qos srr-queue output dscp-map queue 2 threshold 1 32

mls qos srr-queue output dscp-map queue 2 threshold 1 34 36 38

mls qos srr-queue output dscp-map queue 2 threshold 2 24

mls qos srr-queue output dscp-map queue 2 threshold 3 48 56

mls qos srr-queue output dscp-map queue 3 threshold 3 0

mls qos srr-queue output dscp-map queue 4 threshold 1 8

mls qos srr-queue output dscp-map queue 4 threshold 3 10 12 14

mls qos queue-set output 1 threshold 2 70 80 100 100

mls qos queue-set output 1 threshold 4 40 100 100 100

But with this config, the PBX is generating a lot of QoS error logs related to delay and jitter. Because of this i want to change how Signaling (DSCP 24 - CoS 3) will be managed by switches. Could i use this config instead?

mls qos map cos-dscp 0 8 16 24 34 46 48 56

mls qos srr-queue output cos-map queue 1 threshold 3 3 5

mls qos srr-queue output cos-map queue 2 threshold 1 2 4

mls qos srr-queue output cos-map queue 2 threshold 3 6 7

mls qos srr-queue output cos-map queue 3 threshold 3 0

mls qos srr-queue output cos-map queue 4 threshold 3 1

mls qos srr-queue output dscp-map queue 1 threshold 3 24 41 42 43 44 45 46 47

mls qos srr-queue output dscp-map queue 2 threshold 1 16 18 20 22 25 32 34 36

mls qos srr-queue output dscp-map queue 2 threshold 1 38

mls qos srr-queue output dscp-map queue 2 threshold 2 40

mls qos srr-queue output dscp-map queue 2 threshold 3 26 27 28 29 30 31 48 49

mls qos srr-queue output dscp-map queue 2 threshold 3 50 51 52 53 54 55 56 57

mls qos srr-queue output dscp-map queue 2 threshold 3 58 59 60 61 62 63

mls qos srr-queue output dscp-map queue 3 threshold 3 0 17 19 21 23 33 35 37

mls qos srr-queue output dscp-map queue 3 threshold 3 39

mls qos srr-queue output dscp-map queue 4 threshold 1 8

mls qos srr-queue output dscp-map queue 4 threshold 2 9 11 13 15

mls qos srr-queue output dscp-map queue 4 threshold 3 1 2 3 4 5 6 7 10

mls qos srr-queue output dscp-map queue 4 threshold 3 12 14

mls qos queue-set output 1 threshold 1 138 138 92 138

mls qos queue-set output 1 threshold 2 70 80 100 100

mls qos queue-set output 1 threshold 4 40 100 100 100

mls qos

What i´m trying to do here is to locate signaling traffic on output priority queue (1). What about the queue-set output, will that work?. Thanks.

1 Accepted Solution

Accepted Solutions

well signalling is ok to be placed in diffrent queue other than the PQ

just make sure the VOIP RTP marked with cos5/dscp 46 is placed in the PQ and make sure that you have the right cos-to-dscp maping from cos 5 to dscp 46

hope this help

View solution in original post

4 Replies 4

Marwan ALshawi
VIP Alumni
VIP Alumni

mls qos srr-queue input cos-map queue 2 threshold 3 3 5
mls qos srr-queue output cos-map queue 1 threshold 3 5

mls qos srr-queue output dscp-map queue 1 threshold 3 40 41 42 43 44 45 46 47

and on the interface level you the enable PRQ

priority-queue out

i am assuming you are using 3560 switch

HTH

Ok. Let me proccess  this to see if I understand it!

You´re telling me to manage priority for signaling only in the input priority queue (2) (does it matter if i put cos 3 in queue 2 for output?) while voice will be manage here an also y in the ouput priority queue (1)???? So  the hole thing could look like this?

mls qos map cos-dscp 0 8 16 24 34 46 48 56

mls qos srr-queue input cos-map queue 2 threshold 3 3 5 

mls qos srr-queue output cos-map queue 1 threshold 3 5

mls qos srr-queue output cos-map queue 2 threshold 1 2 4

mls qos srr-queue output cos-map queue 2 threshold 2 3

mls qos srr-queue output cos-map queue 2 threshold 3 6 7

mls qos srr-queue output cos-map queue 3 threshold 3 0

mls qos srr-queue output cos-map queue 4 threshold 3 1

mls qos srr-queue output dscp-map queue 1 threshold 3 40 41 42 43 44 45 46 47

mls qos srr-queue output dscp-map queue 2 threshold 1 16 18 20 22 25 32 34 36

mls qos srr-queue output dscp-map queue 2 threshold 1 38

mls qos srr-queue output dscp-map queue 2 threshold 2 24

mls qos srr-queue output dscp-map queue 2 threshold 3 26 27 28 29 30 31 48 49

mls qos srr-queue output dscp-map queue 2 threshold 3 50 51 52 53 54 55 56 57

mls qos srr-queue output dscp-map queue 2 threshold 3 58 59 60 61 62 63

mls qos srr-queue output dscp-map queue 3 threshold 3 0 17 19 21 23 33 35 37

mls qos srr-queue output dscp-map queue 3 threshold 3 39

mls qos srr-queue output dscp-map queue 4 threshold 1 8

mls qos srr-queue output dscp-map queue 4 threshold 2 9 11 13 15

mls qos srr-queue output dscp-map queue 4 threshold 3 1 2 3 4 5 6 7 10

mls qos srr-queue output dscp-map queue 4 threshold 3 12 14

mls qos queue-set output 1 threshold 1 138 138 92 138

mls qos queue-set output 1 threshold 2 70 80 100 100

mls qos queue-set output 1 threshold 4 40 100 100 100

mls qos

I´ve priority-queue out and queue-set 1 applied to all interfaces (including trunks) and yes, i´m usign 3560 switches. Will this be your recommended setting to prioritize signaling?

well signalling is ok to be placed in diffrent queue other than the PQ

just make sure the VOIP RTP marked with cos5/dscp 46 is placed in the PQ and make sure that you have the right cos-to-dscp maping from cos 5 to dscp 46

hope this help

Thanks again dude, thanks for your patience.

This will be my complete config taking in account your suggestions!

mls qos

class-map match-all VoIP
match ip dscp ef
class-map match-all VoIP-SIGNALING
match ip dscp cs5

policy-map QoS-SW3560
class VoIP
set dscp ef
class VoIP-SIGNALING
set dscp cs3

mls qos map cos-dscp 0 8 16 24 34 46 48 56

mls qos srr-queue input cos-map queue 2 threshold 3 3 5

mls qos srr-queue output cos-map queue 1 threshold 3 5
mls qos srr-queue output cos-map queue 2 threshold 1 2 4
mls qos srr-queue output cos-map queue 2 threshold 2 3
mls qos srr-queue output cos-map queue 2 threshold 3 6 7
mls qos srr-queue output cos-map queue 3 threshold 3 0
mls qos srr-queue output cos-map queue 4 threshold 3 1
mls qos srr-queue output dscp-map queue 1 threshold 3 40 41 42 43 44 45 46 47
mls qos srr-queue output dscp-map queue 2 threshold 1 16
mls qos srr-queue output dscp-map queue 2 threshold 1 18 20 22
mls qos srr-queue output dscp-map queue 2 threshold 1 25
mls qos srr-queue output dscp-map queue 2 threshold 1 32
mls qos srr-queue output dscp-map queue 2 threshold 1 34 36 38
mls qos srr-queue output dscp-map queue 2 threshold 2 24
mls qos srr-queue output dscp-map queue 2 threshold 3 48 56
mls qos srr-queue output dscp-map queue 3 threshold 3 0
mls qos srr-queue output dscp-map queue 4 threshold 1 8
mls qos srr-queue output dscp-map queue 4 threshold 3 10 12 14

mls qos queue-set output 1 threshold 1 138 138 92 138
mls qos queue-set output 1 threshold 2 70 80 100 100
mls qos queue-set output 1 threshold 4 40 100 100 100

interface range GigabitEthernet0/X

no mls qos trust dscp

no auto qos voip trust
queue-set 1
srr-queue bandwidth share 1 70 25 5
srr-queue bandwidth shape 3 0 0 0
service-policy input QoS-SW3560
priority-queue out

Now, taking into consideration other comments you have done, what will take precedence for this interface configuration? the queue-set 1 or the priority queue out? should i remove one? and, This whole config looks ok to you?

Thanks again.

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