I wanted to see what happens when you configure egress Qos with SRR. To accomplish this, I create a policy-map which set the DSCP 40 for WWW traffic.
ip access-list extended ACL_HTTP permit tcp any any eq www
class-map match-all CM_HTTP match access-group name ACL_HTTP ! ! policy-map PM_QOS class CM_HTTP set dscp cs5
interface FastEthernet0/1 description laptop mls qos trust device cisco-phone service-policy input PM_QOS
I got a PC and Laptop connected via a Cisco 2960. On the PC I run iperf.exe on the default port and on port 80. On the laptop I have also 2 client iperf running.
Normal traffic is marked as cos-0 and www traffic with DSCP 40. Cos 0 is going to the queue 2 of the egress and DSCP is going to queue 1.
On the PC interface I configured :
interface FastEthernet0/3 description PC srr-queue bandwidth share 10 20 30 40 srr-queue bandwidth shape 10 0 0 0 mls qos trust device cisco-phone
The www traffic is now only 10 Mb/s because shape is limiting also the traffic.
srr-queue bandwidth shape 10 0 0 0 means that Queue 1 is 1/10 of the bandwidth. This is guaranteed and limit.
ssr-queue bandwidth share 10 20 30 40 means that Queue 2 is 20/100 Queue3 is 30/100 and Queue4 is 40/100 of the remaining bandwidth.
Normally all PC traffic is set to COS0 and this will be going into queue 2.
SW2960#sh mls qos maps dscp-out Dscp-outputq-threshold map: d1 :d2 0 1 2 3 4 5 6 7 8 9 ------------------------------------------------------------ 0 : 02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 1 : 02-01 02-01 02-01 02-01 02-01 02-01 03-01 03-01 03-01 03-01 2 : 03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 3 : 03-01 03-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 4 : 01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 04-01 04-01 5 : 04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 6 : 04-01 04-01 04-01 04-01
SW2960#sh mls qos maps cos-out Cos-outputq-threshold map: cos: 0 1 2 3 4 5 6 7 ------------------------------------ queue-threshold: 2-1 2-1 3-1 3-1 4-1 1-1 4-1 4-1
My lab :
Testing the link without any www traffic.
Here is the WWW trafic limited to 10 Mb (1/10 of the 100Mb link)
The other traffic got the remaining bandwidth
The default cos-output-q mapping
Default traffic in Queue1 (Cos0)
I did also some more testing with different queue’s and iperf instances and the bottem line is :
SHAPE = 1/xx of the bandwidth Guaranteed and Limits
SHARE = x / w+x+y+z weight Balance the remaining bandwidth over the queue.
Background information about Qos can be found at :
The basiq QOS model:
Qos flow :
Ingress:
Default Queuing:
Classification and Marking:
With Policed dscp mapping :
With Policing :
Queuing, and Scheduling :
Egress:
