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Changing Scheduling order of Queues on SRX 650

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  • 1.  Changing Scheduling order of Queues on SRX 650

    Posted 10-10-2017 12:36

    Hi everyone,

    Please consider the following set up:

     

    Let say we have mapped 8 traffic class to queues on our SRX 650

    Traffic 0—Q0

    Traffic 1-q1

    Traffic2-q2

    Traffic3 q3

    Traffic4-q4

    Traffic5-q5

    Traffic-q6

    Network Control-q7

     

    If we do not define any scheduler,  will SRX  service queues from high to low queue using default scheduler?

    How about if we want to modify this order for example:

     

    Traffic 0—Q0

    Traffic 1-q1 Scheduler 1, priority high

    Traffic2-q2 Scheduler 2 priority low

    Traffic3 q3 Scheduler 3 priority low

    Traffic4-q4 Scheduler 4 priority low

    Traffic5-q5 Scheduler 5 priority medium

    Traffic-q6 scheduler 6 priority low

    Network Control-q7 scheduler 7 priority low

     

    Will the above config cause queues be serviced in following order?

    Q1 first ( because Scheduler priority is high)

    Q5 second ( because Scheduler priority is medium)

     

    Then rest of them in these order

    Q7

    Q6

    Q4

    Q3

    Q2

    Q0

     

     

     

    Thanks and have a nice day!!



  • 2.  RE: Changing Scheduling order of Queues on SRX 650

     
    Posted 10-10-2017 14:31

    Default schedulers looks like that:

    [edit class-of-service]
    schedulers {
    	network-control {
    		transmit-rate percent 5;
    		buffer-size percent 5;
    		priority low;
    		drop-profile-map loss-priority any protocol any drop-profile terminal;
    	}
    	best-effort {
    		transmit-rate percent 95;
    		buffer-size percent 95;
    		priority low;
    		drop-profile-map loss-priority any protocol any drop-profile terminal;
    	}
    }
    drop-profiles {
    	terminal {
    		fill-level 100 
    		drop-probability 100;
    	}
    }

    It is implicit. It doesn't show in the configuration.

     

    best-effort is assigned to queue 0 and network-control to queue 3. No other queues have resources assigned to them.

    Assigning forwarding-classes to queues will do nothing untill you also assign resources.

     

    If you assign resources and priorities traffic will be forwarded based on WRR Weighted Round Robin. From hight to low (strict-high is an exception and is always serviced first). Priorities matter as logn as traffic is in profile (doesn't exceed assigned resources).

     

    Regards, Wojtek

     



  • 3.  RE: Changing Scheduling order of Queues on SRX 650

    Posted 10-10-2017 14:41

    Thanks,

     I just edited this post based on the" Day one book on COS"

     

    Basically , I am trying to understand what controls the order,  queues  are serviced by scheduler? Is it scheduler's  priority ? is the queue's  priority?

     

    Queue priority:

     

    class-of-service { forwarding-classes {

    class NC queue 7 priority high;

    class EF queue 5 priority high;

    class AF11 queue 4 priority low;

    class AF13 queue 3 priority low;

    class AF22 queue 2 priority low;

    class AF42 queue 1 priority low;

    class BE queue 0 priority low;

    class LBE queue 6 priority low;

     

     

     

    Scheduler priority:

    TR-t.PNG

     

     

    2) How are the queues seviced if the all scedulers are configured same low priority? will then Queue's prioprity decding factor? How about if all queues are low priority low i.e q0 through q7 are configured as low priority?

     

     

    Thanks for your response.

     

     

     

     

     

     



  • 4.  RE: Changing Scheduling order of Queues on SRX 650
    Best Answer

     
    Posted 10-11-2017 01:12

    Traffic is serviced based on priority configured under schedulers.

    Priority configured under forwarding-class is a "fabric priority". It can be either low or high. It is used when you have fabric oversubscription.

     

    Regards, Wojtek



  • 5.  RE: Changing Scheduling order of Queues on SRX 650

    Posted 10-11-2017 15:25

    Thanks for your response.

     What if all schedulers for tarffic classes, (mapped to queues 0-7), have same priority? Will in that case Queues are serviced from Q7 to Q0?

     

     

    Thanks nad have a nice day!!