171 lines
4.8 KiB
Groff
171 lines
4.8 KiB
Groff
.\" $NetBSD: tbrconfig.8,v 1.6 2009/04/08 13:37:43 joerg Exp $
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.\" $KAME: tbrconfig.8,v 1.2 2001/04/09 16:26:30 thorpej Exp $
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.\"
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.\" Copyright (C) 2000
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.\" Sony Computer Science Laboratories Inc. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY SONY CSL AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL SONY CSL OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd July 25, 2000
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.Dt TBRCONFIG 8
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.Os
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.\"
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.Sh NAME
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.Nm tbrconfig
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.Nd configure a token bucket regulator for an output queue
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.\"
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.Sh SYNOPSIS
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.Nm
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.Ar interface
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.Oo
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.Ar tokenrate
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.Op Ar bucketsize
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.Oc
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.Nm tbrconfig
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.Fl d
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.Ar interface
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.Nm tbrconfig
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.Fl a
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.Sh DESCRIPTION
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.Nm
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configures a token bucket regulator for the output network
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interface queue.
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A token bucket regulator limits both the average amount and
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instantaneous amount of packets that the underlying driver can dequeue
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from the network interface within the kernel.
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.Pp
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Conceptually, tokens accumulate in a bucket at the average
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.Ar tokenrate ,
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up to the
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.Ar bucketsize .
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The driver can dequeue packets as long as there are positive amount
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of tokens, and the length of the dequeued packet is subtracted from
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the remaining tokens. Tokens can be negative as a deficit, and
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packets are not dequeued from the interface queue until the tokens
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become positive again.
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The
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.Ar tokenrate
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limits the average rate, and the
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.Ar bucketsize
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limits the maximum burst size.
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.Pp
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Limiting the burst size is essential to packet scheduling, since the
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scheduler schedules packets backlogged at the network interface.
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Limiting the burst size is also needed for drivers which dequeues more
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packets than they can send and end up with discarding excess packets.
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.Pp
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When the
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.Ar tokenrate
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is set to higher than the actual transmission rate, the transmission
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complete interrupt will trigger the next dequeue.
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On the other hand, when the
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.Ar tokenrate
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is set to lower than the actual transmission rate, the transmission
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complete interrupt would occur before the tokens become positive.
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In this case, the next dequeue will be triggered by a timer event.
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Because the kernel timer has a limited granularity, a larger
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.Ar bucketsize
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is required for a higher
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.Ar tokenrate .
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.Pp
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The
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.Ar interface
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parameter is a string of the form
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.Dq name unit ,
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for example,
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.Dq en0 .
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.Pp
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The
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.Ar tokenrate
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parameter specifies the average rate in bits per second, and
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.Dq K
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or
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.Dq M
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can be appended to
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.Ar tokenrate
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as a short hand of
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.Dq Kilo-bps
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or
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.Dq Mega-bps ,
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respectively.
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When
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.Ar tokenrate
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is omitted,
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.Nm
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displays the current parameter values.
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.Pp
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The
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.Ar bucketsize
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parameter specifies the bucket size in bytes, and
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.Dq K
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can be appended to
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.Ar bucketsize
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as a short hand of
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.Dq Kilo-bytes .
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When
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.Ar bucketsize
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is omitted,
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.Nm
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assumes the regulator is driven by transmission complete interrupts
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and, using heuristics, assigns a small bucket size according to the
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.Ar tokenrate .
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When the keyword
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.Dq auto
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is given as
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.Ar bucketsize ,
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.Nm
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assumes the regulator is driven by the kernel timer, and
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computes the bucket size from
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.Ar tokenrate
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and the kernel clock frequency.
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.Pp
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If the
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.Fl d
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flag is passed before an interface name,
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.Nm
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will remove the token bucket regulator for the specified interface.
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.Pp
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Optionally, the
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.Fl a
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flag may be used instead of an interface name. This flag instructs
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.Nm
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to display information about all interfaces in the system.
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.Sh EXAMPLES
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To configure a token bucket regulator for the interface en0 with
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10Mbps token rate and 8KB bucket size,
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.Bd -literal -offset indent
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# tbrconfig en0 10M 8K
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.Ed
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.Pp
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To rate-limit the interface en0 up to 3Mbps,
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.Bd -literal -offset indent
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# tbrconfig en0 3M auto
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.Ed
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.Sh SEE ALSO
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.Xr altq.conf 5 ,
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.Xr altqd 8
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.Sh HISTORY
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The
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.Nm
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command first appeared in WIDE/KAME IPv6 protocol stack kit as part of
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ALTQ tools.
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