Personal Notes on Qos on Cisco 2960

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.

noLimit

 

Here is the WWW trafic limited to 10 Mb (1/10 of the 100Mb link)
10 Mb shape

The other traffic got the remaining bandwidth

85Mb share- 10 mb shape ook bezig

The default cos-output-q mapping

mls qos maps cos-output default

Default traffic in Queue1 (Cos0)

queue

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 :

http://www.cisco.com/c/en/us/support/docs/switches/catalyst-3750-series-switches/91862-cat3750-qos-config.html

 

The basiq QOS model:

BasicQos

Qos flow :

QosOverview

 

Ingress:

Default Queuing:QosDefaultScheduling

Classification and Marking:

QosPortInput

With Policed dscp mapping :

QosPolicedDSCP

With Policing :

QosPolicing

Queuing, and Scheduling :

QosQueueingSchedulingDropping

 

Egress:

 

QosDefaultMapIngress

Be the first to comment

Leave a Reply

Your email address will not be published.


*