{
    "mode": "man",
    "parameter": "tc-drr",
    "section": "8",
    "url": "https://www.chedong.com/phpMan.php/man/tc-drr/8/json",
    "generated": "2026-06-15T14:27:22Z",
    "synopsis": "tc qdisc ... add drr [ quantum bytes ]",
    "sections": {
        "NAME": {
            "content": "drr - deficit round robin scheduler\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "tc qdisc ... add drr [ quantum bytes ]\n\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "The  Deficit  Round  Robin  Scheduler is a classful queuing discipline as a more flexible re‐\nplacement for Stochastic Fairness Queuing.\n\nUnlike SFQ, there are no built-in queues -- you need to add classes and then set  up  filters\nto classify packets accordingly.  This can be useful e.g. for using RED qdiscs with different\nsettings for particular traffic. There is no default class -- if a packet cannot  be  classi‐\nfied, it is dropped.\n\n",
            "subsections": []
        },
        "ALGORITHM": {
            "content": "Each class is assigned a deficit counter, initialized to quantum.\n\nDRR  maintains an (internal) ''active'' list of classes whose qdiscs are non-empty. This list\nis used for dequeuing. A packet is dequeued from the class at the head of  the  list  if  the\npacket  size  is  smaller or equal to the deficit counter. If the counter is too small, it is\nincreased by quantum and the scheduler moves on to the next class in the active list.\n\n\n",
            "subsections": []
        },
        "PARAMETERS": {
            "content": "quantum\nAmount of bytes a flow is allowed to dequeue before the scheduler moves  to  the  next\nclass. Defaults to the MTU of the interface. The minimum value is 1.\n\n",
            "subsections": [
                {
                    "name": "EXAMPLE & USAGE",
                    "content": "To attach to device eth0, using the interface MTU as its quantum:\n\n# tc qdisc add dev eth0 handle 1 root drr\n\nAdding two classes:\n\n# tc class add dev eth0 parent 1: classid 1:1 drr\n# tc class add dev eth0 parent 1: classid 1:2 drr\n\nYou also need to add at least one filter to classify packets.\n\n# tc filter add dev eth0 protocol .. classid 1:1\n\nLike  SFQ,  DRR  is only useful when it owns the queue -- it is a pure scheduler and does not\ndelay packets. Attaching non-work-conserving qdiscs like tbf to it does  not  make  sense  --\nother  qdiscs  in  the active list will also become inactive until the dequeue operation suc‐\nceeds. Embed DRR within another qdisc like HTB or HFSC to ensure it owns the queue.\n\nYou can mimic SFQ behavior by assigning packets to the attached classes using the  flow  fil‐\nter:\n"
                },
                {
                    "name": "tc qdisc add dev .. drr",
                    "content": ""
                },
                {
                    "name": "for i in .. 1024;do",
                    "content": "tc class add dev .. classid $handle:$(print %x $i)\ntc qdisc add dev .. fifo limit 16"
                },
                {
                    "name": "done",
                    "content": "tc  filter add .. protocol ip .. $handle flow hash keys src,dst,proto,proto-src,proto-dst di‐‐"
                },
                {
                    "name": "visor 1024 perturb 10",
                    "content": ""
                }
            ]
        },
        "SOURCE": {
            "content": "o      M. Shreedhar and George Varghese \"Efficient Fair Queuing using Deficit  Round  Robin\",\nProc. SIGCOMM 95.\n\n",
            "subsections": []
        },
        "NOTES": {
            "content": "This  implementation  does  not drop packets from the longest queue on overrun, as limits are\nhandled by the individual child qdiscs.\n\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "tc(8), tc-htb(8), tc-sfq(8)\n\n",
            "subsections": []
        },
        "AUTHOR": {
            "content": "scheddrr was written by Patrick McHardy.\n\n\n\niproute2                                    January 2010                                       TC(8)",
            "subsections": []
        }
    },
    "summary": "drr - deficit round robin scheduler",
    "flags": [],
    "examples": [],
    "see_also": [
        {
            "name": "tc",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/tc/8/json"
        },
        {
            "name": "tc-htb",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/tc-htb/8/json"
        },
        {
            "name": "tc-sfq",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/tc-sfq/8/json"
        }
    ]
}