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How to stop Tail drop and Red Drop in MX204?

  • 1.  How to stop Tail drop and Red Drop in MX204?

    Posted 02-06-2023 04:50
    Hello my friends,

    I noticed recently that my Juniper MX204 et interface has some tail drop and red drop as image below:



    I have also checked my class-of-service drop-profile and found:
    Drop profile: <default-drop-profile>, Type: discrete, Index: 1
    Fill level                         Drop probability
    100                                  100

    I have not set up any Fill Level on my MX204, I know that if the queue buffer size fill level is 100, the probability of packet drop is also 100%. We use MX204 as a BNG and noticed that some customers are complaining for packet loss and low bandwidth. 

    What will be the possible solution? If anybody can guide me please.

    Thanks

    ------------------------------
    Nazmus Sakib
    ------------------------------


  • 2.  RE: How to stop Tail drop and Red Drop in MX204?

    Posted 02-06-2023 10:09
    Hello Sakib, 

    By default, even if you do not configure COS on your device, RED is still in effect and functions as the primary mechanism for managing congestion. In the default RED drop profile, when the fill level is 0 percent, the drop probability is 0 percent. When the fill level is 100 percent, the drop probability is 100 percent. The TAIL drop profile is also active by default acting as backup mechanisms to tackle congestion with the same principles of 0 % fill level means 0% drop probability and 100% fill level suggesting 100 % drop probability . When you have packets enqueued which is more than you could send, you might see RED drop. If the enqueueing packets come too fast and it even can't be enqueued (ie. the current queue size is reaching max), you will see tail drop.
     
    In the situation when you RED and/or TAIL drops are observed on an interface and no COS configuration is made on the box you have a number of solutions:
     
    • Increase bandwidth on egress interfaces - this can be done by replacing the interface where you observe the drops with an AE bundle
    • Use traffic shaping to throttle traffic from the source
    • Configure a classifier to put mission critical applications data to a queue other than the best effort queue. Then, allocate enough bandwidth and buffer to that queue. This effectively allows less drops on mission critical applications data at the expense of other application data that are using the best effort queue
    Thanks 
    Ruban Johnson

    ------------------------------
    RUBAN JOHNSON
    ------------------------------

    Original Message


  • 3.  RE: How to stop Tail drop and Red Drop in MX204?

    Posted 02-07-2023 12:18
    Thanks Ruban,
    Our configuration is already on et interface and the pic has been configured at 40G. We are using CoS shaping on MX204.
    One thing I doubt that we recently changed our whole FPC, PIC settings on MX204. Among the four on PIC0, port0: 40G, Port1: 40G, Port2: 100G and port3: 100G
    Although we are not using 100G ports at this moment.
    If we use classifier or policer COS shaping on QFX instead of MX204, is there any improvement can we expect?

    Thanks for your cooperation

    ------------------------------
    Nazmus Sakib
    ------------------------------

    Original Message


  • 4.  RE: How to stop Tail drop and Red Drop in MX204?

    Posted 02-08-2023 07:10
    Hello Sakib, 

    Can you please provide your cos and the interface configurations ? 

    i dont see the drops are regular as we dont see any at the time you have taken the output. Do you see your interface graphs for any micro bursts happening ?

    Do you see drops only at best effort or its happening in all your queues ?

    If we use classifier or policer COS shaping on QFX instead of MX204, is there any improvement can we expect?

    yes, you can try that as well 

    Thanks 
    Ruban Johnson


    ------------------------------
    RUBAN JOHNSON
    ------------------------------

    Original Message


  • 5.  RE: How to stop Tail drop and Red Drop in MX204?

    Posted 02-10-2023 06:25

    This is the interface which is used for customer downlink to Juniper QFX5110:

    show configuration interfaces et-0/0/0
    description "DOWNLINK SW2 et-0/0/48 40Gb";
    enable;
    traceoptions {
        flag all;
    }
    hierarchical-scheduler maximum-hierarchy-levels 3 implicit-hierarchy;
    flexible-vlan-tagging;
    auto-configure {
        stacked-vlan-ranges {
            dynamic-profile vlan-ps {
                accept pppoe;
                ranges {
                    any,any;
                }
            }
        }
        vlan-ranges {
            dynamic-profile vlan-ps {
                accept pppoe;
                ranges {
                    any;
                }
            }
        }
        remove-when-no-subscribers;
    }
    mtu 2000;
    encapsulation flexible-ethernet-services;
    unit 1 {
        vlan-id 1;
        family inet {
            address 192.168.100.2/24;
        }
        family iso;
    }
    unit 202 {
        encapsulation vlan-bridge;
        vlan-tags outer 202 inner 4093;
    }
    unit 203 {
        encapsulation vlan-bridge;
        vlan-tags outer 203 inner 4093;
    }
    unit 4093 {
        encapsulation vlan-bridge;
        vlan-id 4093;
    }

    We have configured Class of Service under the dynamic profile like that:

    class-of-service {
                traffic-control-profiles {
                    50m {
                        shaping-rate 50m;
                    }
                    200m {
                        shaping-rate 200m;
                    }
                    1g {
                        shaping-rate 2g;
                    }
                    100m {
                        shaping-rate 110m;
                    }
                    250m {
                        shaping-rate 310m;
                    }
                    300m {
                        shaping-rate 310m;
                    }
                    10g {
                        shaping-rate 12g;
                    }



    ------------------------------
    Nazmus Sakib
    ------------------------------

    Original Message


  • 6.  RE: How to stop Tail drop and Red Drop in MX204?

    Posted 02-10-2023 11:26

    Hello Sakib, 

    So i understand this is a new 40g link, dont we need a new traffic-control-profile for them with a shaping rate ? i do see for 10g but nothing added for 40g ? whats been added for this interface ? you can check with the below command 

    show class-of-service interface et-0/0/0

    show class-of-service interface et-0/0/0 detail 

    Thanks

    Ruban 



    ------------------------------
    RUBAN JOHNSON
    ------------------------------

    Original Message


  • 7.  RE: How to stop Tail drop and Red Drop in MX204?