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The inflight bandwidth limiter was removed in r212765.

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andre 2010-09-16 22:11:55 +00:00
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@ -32,7 +32,7 @@
.\" From: @(#)tcp.4 8.1 (Berkeley) 6/5/93
.\" $FreeBSD$
.\"
.Dd August 16, 2008
.Dd September 16, 2010
.Dt TCP 4
.Os
.Sh NAME
@ -383,72 +383,6 @@ code.
For this reason, we use 200ms of slop and a near-0
minimum, which gives us an effective minimum of 200ms (similar to
.Tn Linux ) .
.It Va inflight.enable
Enable
.Tn TCP
bandwidth-delay product limiting.
An attempt will be made to calculate
the bandwidth-delay product for each individual
.Tn TCP
connection, and limit
the amount of inflight data being transmitted, to avoid building up
unnecessary packets in the network.
This option is recommended if you
are serving a lot of data over connections with high bandwidth-delay
products, such as modems, GigE links, and fast long-haul WANs, and/or
you have configured your machine to accommodate large
.Tn TCP
windows.
In such
situations, without this option, you may experience high interactive
latencies or packet loss due to the overloading of intermediate routers
and switches.
Note that bandwidth-delay product limiting only effects
the transmit side of a
.Tn TCP
connection.
.It Va inflight.debug
Enable debugging for the bandwidth-delay product algorithm.
.It Va inflight.min
This puts a lower bound on the bandwidth-delay product window, in bytes.
A value of 1024 is typically used for debugging.
6000-16000 is more typical in a production installation.
Setting this value too low may result in
slow ramp-up times for bursty connections.
Setting this value too high effectively disables the algorithm.
.It Va inflight.max
This puts an upper bound on the bandwidth-delay product window, in bytes.
This value should not generally be modified, but may be used to set a
global per-connection limit on queued data, potentially allowing you to
intentionally set a less than optimum limit, to smooth data flow over a
network while still being able to specify huge internal
.Tn TCP
buffers.
.It Va inflight.stab
The bandwidth-delay product algorithm requires a slightly larger window
than it otherwise calculates for stability.
This parameter determines the extra window in maximal packets / 10.
The default value of 20 represents 2 maximal packets.
Reducing this value is not recommended, but you may
come across a situation with very slow links where the
.Xr ping 8
time
reduction of the default inflight code is not sufficient.
If this case occurs, you should first try reducing
.Va inflight.min
and, if that does not
work, reduce both
.Va inflight.min
and
.Va inflight.stab ,
trying values of
15, 10, or 5 for the latter.
Never use a value less than 5.
Reducing
.Va inflight.stab
can lead to upwards of a 20% underutilization of the link
as well as reducing the algorithm's ability to adapt to changing
situations and should only be done as a last resort.
.It Va rfc3042
Enable the Limited Transmit algorithm as described in RFC 3042.
It helps avoid timeouts on lossy links and also when the congestion window