3750-SRR

Unanswered Question
Dec 8th, 2009
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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.

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PAUL CHEN Tue, 12/08/2009 - 06:46
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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 Tue, 12/08/2009 - 06:59
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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


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 Wed, 12/16/2009 - 08:08
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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 Sun, 02/21/2010 - 16:10
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lamav wrote:


Interesting topic...


Was just reading some QoS material...


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


Yep


Is it used in conjunction with others?


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


It has it's own structure but you can use some of the MQC elements but only on input


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


On switches such as 3560/3750 etc


Thanks

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