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+.\"	$OpenBSD: tbrconfig.8,v 1.1 2001/06/27 18:23:36 kjc Exp $
+.\"	$KAME: tbrconfig.8,v 1.2 2001/04/09 16:26:30 thorpej Exp $
+.\"
+.\" Copyright (C) 2000
+.\" Sony Computer Science Laboratories Inc.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY SONY CSL AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL SONY CSL OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.Dd July 25, 2000
+.Dt TBRCONFIG 8
+.Os KAME
+.\"
+.Sh NAME
+.Nm tbrconfig
+.Nd configure a token bucket regulator for an output queue
+.\"
+.Sh SYNOPSIS
+.Nm
+.Ar interface
+.Oo
+.Ar tokenrate
+.Op Ar bucketsize
+.Oc
+.Nm tbrconfig
+.Fl d
+.Ar interface
+.Nm tbrconfig
+.Fl a
+.Sh DESCRIPTION
+.Nm
+configures a token bucket regulator for the output network
+inteface queue.
+A token bucket regulator limits both the average amount and
+instantaneous amount of packets that the underlying driver can dequeue
+from the network interface within the kernel.
+.Pp
+Conceptually, tokens accumulate in a bucket at the average
+.Ar tokenrate ,
+up to the
+.Ar bucketsize .
+The driver can dequeue packets as long as there are positive amount
+of tokens, and the length of the dequeued packet is subtracted from
+the remaining tokens.  Tokens can be negative as a deficit, and
+packets are not dequeued from the interface queue until the tokens
+become positive again.
+The
+.Ar tokenrate
+limits the average rate, and the
+.Ar bucketsize
+limits the maximum burst size.
+.Pp
+Limiting the burst size is essential to packet scheduling, since the
+scheduler schedules packets backlogged at the network interface.
+Limiting the burst size is also needed for drivers which dequeues more
+packets than they can send and end up with discarding excess packets.
+.Pp
+When the
+.Ar tokenrate
+is set to higher than the actual transmission rate, the transmission
+complete interrupt will trigger the next dequeue.
+On the other hand, when the
+.Ar tokenrate
+is set to lower than the actual transmission rate, the transmission
+complete interrupt would occur before the tokens become positive.
+In this case, the next dequeue will be triggered by a timer event.
+Because the kernel timer has a limited granularity, a larger
+.Ar bucketsize
+is required for a higher
+.Ar tokenrate .
+.Pp
+The
+.Ar interface
+parameter is a string of the form
+.Dq name unit ,
+for example,
+.Dq en0 .
+.Pp
+The
+.Ar tokenrate
+parameter specifies the average rate in bits per second, and
+.Dq K
+or
+.Dq M
+can be appended to
+.Ar tokenrate
+as a short hand of
+.Dq Kilo-bps
+or
+.Dq Mega-bps ,
+respectively.
+When
+.Ar tokenrate
+is omitted,
+.Nm
+displays the current parameter values.
+.Pp
+The
+.Ar bucketsize
+parameter specifies the bucket size in bytes, and
+.Dq K
+can be appended to
+.Ar bucketsize
+as a short hand of
+.Dq Kilo-bytes .
+When
+.Ar bucketsize
+is omitted,
+.Nm
+assumes the regulator is driven by transmission complete interrupts
+and, using heuristics, assigns a small bucket size according to the
+.Ar tokenrate .
+When the keyword
+.Dq auto
+is given as
+.Ar bucketsize ,
+.Nm
+assumes the regulator is driven by the kernel timer, and
+computes the bucket size from
+.Ar tokenrate
+and the kernel clock frequency.
+.Pp
+If the
+.Fl d
+flag is passed before an interface name,
+.Nm
+will remove the token bucket regulator for the specified interface.
+.Pp
+Optionally, the
+.Fl a
+flag may be used instead of an interface name.  This flag instructs
+.Nm
+to display information about all interfaces in the system.
+.Sh EXAMPLES
+To configure a token bucket regulator for the interface en0 with
+10Mbps token rate and 8KB bucket size,
+.Bd -literal -offset
+# tbrconfig en0 10M 8K
+.Ed
+.Pp
+To rate-limit the interface en0 up to 3Mbps,
+.Bd -literal -offset
+# tbrconfig en0 3M auto
+.Ed
+.Sh SEE ALSO
+.Xr altq.conf 5 ,
+.Xr altqd 8
+.Sh HISTORY
+The
+.Nm
+command first appeared in WIDE/KAME IPv6 protocol stack kit as part of
+ALTQ tools.