{
    "mode": "info",
    "parameter": "tc-pfifo_fast",
    "section": "",
    "url": "https://www.chedong.com/phpMan.php/info/tc-pfifo_fast/json",
    "generated": "2026-07-05T13:24:36Z",
    "sections": {
        "NAME": {
            "content": "pfifofast - three-band first in, first out queue\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "pfifofast is the default qdisc of each interface.\n\nWhenever an interface is created, the pfifofast qdisc is automatically\nused as a queue. If another qdisc is attached, it preempts the  default\npfifofast,  which  automatically  returns to function when an existing\nqdisc is detached.\n\nIn this sense this qdisc is magic, and unlike other qdiscs.\n",
            "subsections": []
        },
        "ALGORITHM": {
            "content": "The algorithm is very similar to that of the classful tc-prio(8) qdisc.\npfifofast is like three tc-pfifo(8) queues side by side, where packets\ncan be enqueued in any of the three bands based on their Type  of  Ser-\nvice bits or assigned priority.\n\nNot  all  three  bands  are  dequeued simultaneously - as long as lower\nbands have traffic, higher bands are never dequeued. This can  be  used\nto prioritize interactive traffic or penalize 'lowest cost' traffic.\n\nEach  band  can  be  txqueuelen packets long, as configured with ifcon-\nfig(8) or ip(8).  Additional packets coming in are not enqueued but are\ninstead dropped.\n\nSee tc-prio(8) for complete details on how TOS bits are translated into\nbands.\n",
            "subsections": []
        },
        "PARAMETERS": {
            "content": "txqueuelen\nThe length of the three bands depends on the interface  txqueue-\nlen, as specified with ifconfig(8) or ip(8).\n",
            "subsections": []
        },
        "BUGS": {
            "content": "Does  not maintain statistics and does not show up in tc qdisc ls. This\nis because it is the automatic default in the absence of  a  configured\nqdisc.\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "tc(8)\n",
            "subsections": []
        },
        "AUTHORS": {
            "content": "Alexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru>\n\nThis manpage maintained by bert hubert <ahu@ds9a.nl>\n\niproute2                        10 January 2002                  PFIFOFAST(8)",
            "subsections": []
        }
    },
    "summary": "pfifofast - three-band first in, first out queue",
    "flags": [],
    "examples": [],
    "see_also": [
        {
            "name": "tc",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/tc/8/json"
        }
    ]
}