.\" Jean II - HPLB - 96
.\" iwconfig.8
.\"
.TH IWCONFIG 8 "31 October 1996" "net-tools" "Linux Programmer's Manual"
.\"
.\" NAME part
.\"
.SH NAME
iwconfig \- configure a wireless network interface
.\"
.\" SYNOPSIS part
.\"
.SH SYNOPSIS
.BI "iwconfig [" interface ]
.br
.BI "iwconfig " interface " [essid " X "] [nwid " N "] [freq " F "] [channel " C ]
.br
.BI "                   [sens " S "] [enc " E "] [ap " A "] [nick " NN ]
.br
.BI "                   [rate " R "] [rts " RT "] [frag " FT ]
.\"
.\" DESCRIPTION part
.\"
.SH DESCRIPTION
.B Iwconfig
is similar to
.IR ifconfig (8),
but is dedicated to the wireless interfaces. It is used to set the
parameters of the network interface which are specific to the wireless
operation (for example : the frequency).
.B Iwconfig
may also be used to display those parameters, and the wireless
statistics (extracted from
.IR /proc/net/wireless ).
.PP
All these parameters and statistics are device dependant. Each driver
will provide only some of them depending on the hardware support, and
the range of value may change. Please refer to the man page of each
device for details.
.\"
.\" PARAMETER part
.\"
.SH PARAMETERS
.TP
.B essid
Set the ESSID (or Network Name - in some products it may also called
Domain ID). The ESSID is used to identify cells which are part of the
same virtual network.
.br
As opposed to the NWID which defines a single cell, the ESSID defines
a group of cell connected via repeaters or infrastructure, where the
user may roam.  With some card, you may disable the ESSID checking
(ESSID promiscuous) with
.IR off " (and " on
to reenable it).
.TP
.BR nwid / domain
Set the Network ID (in some products it is also called Domain ID). As
all adjacent wireless networks share the same medium, this parameter
is used to differenciate them (create logical colocated networks) and
identify nodes belonguing to the same cell. With some card, you may
disable the Network ID checking (NWID promiscuous) with
.IR off " (and " on
to reenable it).
.TP
.BR freq / channel
Set the operating frequency or channel in the device. Value below 1000
are the channel number, value over this is the frequency in Hz. You
must prepend the suffix k, M or G to the value (for example, "2.46G"
for 2.46 GHz frequency), or add enough '0'.
.br
Channels are usually numbered starting at 1,
and you may use
.IR iwpriv (8)
to get the total number of channels and list the available
frequencies. Depending on regulations, some frequencies/channels may
not be available.
.TP
.B sens
Set the sensitivity threshold. This is the lowest signal level for
which we attempt a packet reception, signal lower than this are not
received. This is used to avoid receiving background noise, so you
should set it according to the average noise level. Positive values
are assumed to be the raw value used by the hardware or a percentage,
negative values are assumed to be dBm.
.br
With some hardware, this parameter also control the defer threshold
(lowest signal level for which we consider the channel busy) and the
handover threshold (lowest signal level where we stay associated with
the current access point).
.TP
.B enc
Set the encryption or scrambing key (the syntax is
.IR XXXX-XXXX-XXXX-XXXX " or " XXXXXXXX ).
Used also to control the encryption feature
.RI ( on / off ).
.TP
.B ap
Register to the Access Point given by the address, if it is
possible. When the quality of the connection goes too low, the driver
may revert back to automatic mode.
.TP
.BR nick [ name ]
Set the nickname, or the station name. Most 802.11 products do define
it, but this is not used as far as the protocols (MAC, IP, TCP) are
concerned and completely accessory as far as configuration goes. In
fact only some diagnostic tools may use it.
.TP
.BR rate / bit [ rate ]
For cards supporting multiple bit rates, set the bit-rate in b/s. The
bit-rate is the speed at which bits are transmitted over the medium,
the user speed of the link is lower due to medium sharing and
overhead.
.br
You must prepend the suffix k, M or G to the value (decimal multiplier
: 10^3, 10^6 and 10^9 b/s), or add enough '0'. Values below 1000 are
card specific, usually an index in the bit-rate list. Use
.I auto
to select the automatic bit-rate mode (fallback to lower rate on noisy
channels), which is the default for most cards, and
.I fixed
to revert back to fixed setting.
.TP
.BR rts [ _threshold ]
RTS/CTS adds a handshake before each packet transmission to make sure
that the channel is clear. This adds overhead, but increase
performance in case of hidden nodes or large number of active
nodes. This parameters set the size of the smallest packet for which
the node sends RTS, a value equal to the maximum packet size disable
the scheme. You may also set this parameter to
.IR auto ", " fixed " or " off .
.TP
.BR frag [ mentation_threshold ]
Fragmentation allow to split a IP packet in a burst of smaller
fragments transmitted on the medium. In most cases this adds overhead,
but in very noisy environment this reduce the error penalty. This
parameter set the maximum fragment size, a value equal to the maximum
packet size disable the scheme. You may also set this parameter to
.IR auto ", " fixed " or " off .
.\"
.\" DISPLAY part
.\"
.SH DISPLAY
For each device which support wireless extensions,
.I iwconfig
will display the name of the
.B MAC protocol
used (name of device for proprietary protocols), the
.B ESSID
(Network Name), the
.BR NWID ,
the
.B frequency
(or channel), the
.BR sensitivity ,
the
.B Access Point
address, the
.B bit-rate
(with
.B (f)
if fixed), the
.BR "RTS threshold" ", the " "fragmentation threshold" ,
and the
.B encryption key
(depending on availability). See above for explanations.
.PP
If
.I /proc/net/wireless
exists,
.I iwconfig
will also display its content :
.TP
.B Link quality
Quality of the link or the modulation (how good the received signal is).
.TP
.B Signal level
Received signal strength (how strong the received signal is).
.TP
.B Noise level
Background noise level (when no packet is transmited).
.TP
.B invalid nwid
Number of packets received with a different NWID. Used to detect
configuration problems or adjacent network existence.
.TP
.B invalid crypt
Number of packets that the hardware was unable to decrypt.
.TP
.B invalid misc
Other packets lost in relation with specific wireless operations.
.\"
.\" AUTHOR part
.\"
.SH AUTHOR
Jean Tourrilhes \- jt@hplb.hpl.hp.com
.\"
.\" FILES part
.\"
.SH FILES
.I /proc/net/wireless
.\"
.\" SEE ALSO part
.\"
.SH SEE ALSO
.BR ifconfig (8),
.BR iwspy (8),
.BR iwpriv (8),
.BR wavelan (4),
.BR wavelan_cs (4),
.BR xircnw_cs (4).