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RED drops non congested AE link

  • 1.  RED drops non congested AE link

    Posted 01-26-2021 13:06
    Howdy.  Is it possible to have RED tail drops on a non congested AE link. We have a cluster of EX4550 with an AE link to a MX PE router. The below output suggest RED drops on a 20G AE that is not congested. This is on the output queue towards the MX. We dont see any other link or physical issues as we have swapped the link and also the optics. The drops are seen on both member interfaces. 

    Interface: ae11, Enabled, Link is Up

    Encapsulation: Ethernet, Speed: 20000mbps

    Traffic statistics:                                              Current delta

      Input bytes:            39356980740060 (5229445888 bps)        [10760491059]

      Output bytes:           61840660176773 (9700835840 bps)        [18059658838]

      Input packets:             39467416568 (643979 pps)               [10642756]

      Output packets:            53397022640 (982784 pps)               [15164634]

    Error statistics:

      Input errors:                        0                                   [0]

      Input drops:                         0                                   [0]

      Input framing errors:                0                                   [0]

      Carrier transitions:                 2                                   [0]

      Output errors:                       0                                   [0]

      Output drops:                 48981479                               [26405]


      Queue counters:       Queued packets  Transmitted packets      Dropped packets

        0                                0          53433737407             49036582

        1                                0                    0                    0

        5                                0                    0                    0

        7                                0              1267216                    0

  • 2.  RE: RED drops non congested AE link

    Posted 02-03-2021 09:01

    Can you check if any tail-drops?

    show interfaces queue ae11



  • 3.  RE: RED drops non congested AE link

    Posted 02-04-2021 13:45

    Regarding output utilization in bps

    Output bytes: 61840660176773 (9700835840 bps)

    Please check if one child link is overutilized, untill another one has no traffic.

    Best regards


  • 4.  RE: RED drops non congested AE link

    Posted 02-09-2021 16:13
    Did you get this sorted? You have a 2 x 10 G link that is loaded to 50 %. I often see links less loaded that experience packet loss due to tail drops. The EX4550 has quite small interface buffers so you need to take that into account. I'd say you're experiencing microbursts where occasionally traffic from several interfaces hit the LAG and you get a queue of packets that grows and in a few milliseconds fills the buffer. Working with class of service/QoS might mitigate this. Start by setting the shared buffer pool to 100 % and see if it makes a difference. If you want more help, please report back!