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Queue Buffer on MX5 Dynamic ?

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  • 1.  Queue Buffer on MX5 Dynamic ?

    Posted 10-28-2017 12:47

    Hi everybody


    When we define Queue buffer say 10% , for EF queue, is this queue limited to 10% even if there is unused buffer available in the pool?


    The reason I ask because I am reading  " MX series " book which says Trio based MPC, uses queue defined buffer size as maximum. But it is for MPC, I was wondering if the same is true for MX5 which is not using any MPC module.


    Thanks and have a nice weekend!!

  • 2.  RE: Queue Buffer on MX5 Dynamic ?
    Best Answer

    Posted 10-29-2017 09:32




    MX5 also belongs to Junos Trio Chipset family.




    With the Trio chipset on the MPCs, WRED drops are performed at the tail of the queue. The packet buffer is organized into 128-byte units. Before a packet is queued, buffer and WRED checks are performed, and the decision to drop is made at this time. Once a packet is queued, it is not dropped. As a result, dynamic buffer allocation is not supported on the Packet Forwarding Engines containing the Trio chipset. The buffer allocation per queue on the Packet Forwarding Engines containing the Trio chipset is considered the maximum for that queue. Once the allocated buffer becomes full, subsequent packets are dropped until space is available, even if other queues are idle. Buffering is only required during oversubscription. To provide larger buffers on Packet Forwarding Engines with the Trio chipset, the delay buffer can be increased from the default 100 ms to 200 ms of the port speed. The delay buffer can also be oversubscribed using the delay-buffer-rate configuration per port.