3750-SRR

PAUL CHEN · ‎12-08-2009

Hi,

I am trying to understand srr on the 3750 switches.

Say, if I need to assign cos values to queues

For example, Cos 1 to PQ, Cos 2,3,4 to Queue 2, Cos 5,6 to Queue 3 and Cos 1 to Queue 4.

Would this be correct ? What threshold number can I use, I am just arbitarily using 3 . I don't really understand the use of threshold here.

I was just following some example posted on the web.

mls qos srr-queue output cos-map queue 1 threshold 3 1
mls qos srr-queue output cos-map queue 2 threshold 3 2,3,4
mls qos srr-queue output cos-map queue 3 threshold 3 5,6
mls qos srr-queue output cos-map queue 4 threshold 3 1

Then if I need to assign bandwidth in percentages

Q1-33,Q2-20,Q3-40, Q4 (adding 40 myself to make it a 100%)

I assume bandwidth share should all add up to 100%

I am not sure if the output here is correct ?

int fa 1/0/11
queue set 1
srr-queue bandwidth share 1 20 40 40
srr-queue bandwidth shape 3 0 0 0
priority-queue out

switch #sh mls qos interface fastEthernet 1/0/11 queueing
FastEthernet1/0/11
Egress Priority Queue : enabled
Shaped queue weights (absolute) : 3 0 0 0
Shared queue weights : 1 20 40 40
The port bandwidth limit : 100 (Operational Bandwidth:100.0)
The port is mapped to qset : 1

Any help appreciated.

Thank you.

Reza Sharifi · ‎12-08-2009

Hi Paul

Please refer to Cisco Config Guide (link below) for some examples on how to configure your COS values.

http://www.ciscosystems.org.ro/en/US/docs/switches/lan/catalyst3750/software/release/12.2_25_sea/command/reference/3750CR.pdf

HTH

Reza

PAUL CHEN · ‎12-08-2009

Hi Reza,

Thanks for the reply. I have seen that document. My Cos values are random. I just want to know if the method and configuration is correct.

I don't understand how thresholds are used.

Regards,

Paul

Jon Marshall · ‎12-08-2009

pjchen wrote:

Hi Reza,

Thanks for the reply. I have seen that document. My Cos values are random. I just want to know if the method and configuration is correct.

I don't understand how thresholds are used.

Regards,

Paul

Thresholds in a queue are in effect a way to specify a drop probability if there are multiple CoS values mapped to the same queue. Sorry to point to another link but have a quick read of this specific section and see if it makes more sense. If it doesn't then come back -

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_46_se/configuration/guide/swqos.html#wp1160918

Jon

lamav · ‎12-16-2009

Interesting topic...

Was just reading some QoS material...

So, is SRR a queueing mechanism like WRR, WFQ, CQWFQ, etc?

Is it used in conjunction with others?

Is it used with classicifaction and marking, as in an MQC architecture?

trying to figure out where this specifric technology comes into play and on what platforms and what circumstances it is used...

Thanks

TodirascuOvidiu · ‎02-21-2010

lamav wrote: