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Buffer size Ex9200 line card

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  • 1.  Buffer size Ex9200 line card

    Posted 05-26-2020 19:03

    Hi

    does anyone know buffer size on the Switch EX9200 line card? I can not find it from Juniper Portal

    is there any suggestion to deduct the packet drop because of the different buffer sizes between vendor devices?

     

    thanks

     



  • 2.  RE: Buffer size Ex9200 line card
    Best Answer

    Posted 05-26-2020 21:52

    Hello cuong.nguyenquoc,

     

    The buffer size is the amount of time in milliseconds of port bandwidth that a queue can use to continue to transmit packets during periods of congestion, before the buffer runs out and packets begin to drop.

     

    On EX Series switches except EX4300 switches, the default scheduler transmission rate and buffer size percentages for queues 0 through 7 are 95, 0, 0, 0, 0, 0, 0, and 5 percent, respectively. On EX4300 switches, the default scheduler transmission rate and buffer size for queues 0 through 11 are 75, 0, 0, 5, 0, 0, 0, 0, 15, 0, 0 and 5 percent, respectively, of the total available buffer.

     

    To deduct packet drop on a specific queue, you can check which queue is getting packet bursts and dropping more packets. Depending on that, you can specify the buffer-size in the scheduler configuration.

     

    Use a scheduler map to map the scheduler to the forwarding class that is mapped to the queue to which you want to apply the buffer size.

     

    For example, suppose that you want to change the dedicated buffer allocation for FCoE traffic. FCoE traffic is mapped to the fcoe forwarding class, and the fcoe forwarding class is mapped to queue 3 (this is the default configuration). To use default FCoE traffic mapping, in the scheduler map configuration, map the scheduler to the fcoe forwarding class.

    How to configure it, you can find it as below.

    https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/cos-configuring-the-scheduler-buffer-size.html

     

    Hope this answers your query.



  • 3.  RE: Buffer size Ex9200 line card

    Posted 05-27-2020 07:50
    Hi Víhaal,
    Thanks your valuable information
    Your suggestion make me more confident. Is there any public information in terms of physical buffer capacity on EX9200 Linecard?

    Good day
    Cuong


  • 4.  RE: Buffer size Ex9200 line card

    Posted 05-27-2020 22:07

    Hello Cuong,

     

    The buffer capacity usually depends on the type of the line card. By default the buffer capacity is 100ms for ports 1g and higher for an Ethernet port which is distributed to the queues configured on that port. Few of the newer line card also support 250ms as well.

     

    Just to give you an instance:

    Calculation for a single 10gig port with default config is 125MB
    100ms for interface (125MByte)=(100/1000)*10*1000000000/8

     

    I tried finding it but couldn't find a public facing document for it though.