srr-queue bandwidth & qos on a 3560

[phil_carter]

Hello,

I have a WS-C3560C-8PC-S running c3560c405-universalk9-mz.122-55.EX3 (ipbaase licence) and have the below qos configured:

interface FastEthernet0/5

description Q-in-Q to <cust-network>

switchport access vlan 20

switchport mode dot1q-tunnel

speed 100

duplex full

mls qos cos 1

mls qos cos override

!

interface FastEthernet0/1

description facing eth-WAN-link-to-far-end

switchport trunk encapsulation dot1q

switchport mode trunk

speed 100

duplex full

srr-queue bandwidth share 12 5 1 2

mls qos trust cos

!

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

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

mls qos srr-queue output cos-map queue 3 threshold 1 0 4 6 7

mls qos srr-queue output cos-map queue 4 threshold 1 5

!

mls qos queue-set output 1 buffers 60 25 5 10

!

I have marked a customer in a particular cos value for all packets coming into my switch, and then mapped that cos value to a queue and threshold within that queue-set (assigned 60% of available buffers). I have then applied SRR share output queueing on the uplink to ensure the customer gets 60% of bandwidth effectively in times of congestion (it gets served 12 times out of every 20 packets if all queues are full).Nothing else is on the switch currently, just this one end customer.

Before applying QoS I could run an ethernet tester at 80m through the link to the far end with no loss of perfomance issues (80m seen at far end). Now I have applied the above QoS config however, the QoS settings kick in immediately, with the tester dropping down to 4m max. The threshold is being hit and dropping packets on the egress queue on the uplink.

My questions are:

1) why is QoS kicking in anyway given the link isnt congested?

2) why is is reducing it to 4m only given the buffers/srr-queue bandwidth are set to 60%?

Help much appreciated, thanks

Phil

[phil_carter]

Also - if I place the customer in cos 4 (for instance), and into another output queue, it runs at 80m fine with no drops.... seems to be a problem with queue 1 only....

Any help/advice appreciated.

[Joseph W. Doherty · Accepted solution]

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Posting

Is the default shaping enabled for Q1, at 4%?

PS:

Trying adding

srr-queue bandwidth shape 0 0 0 0

to your interface.