wl -- T1 speed ISA/radio lan card
device wl0 at isa? port 0x300 irq 5
The wl driver controls a radio lan card system made originally by NCR,
then ATT, now Lucent. The system is spread-spectrum radio at around 915
MHz (or 2.4 GHz). With the supplied omni-directional antennae, about 400
feet (indoors, more outdoors) can be covered in circumference. This card
can talk to the companion (wlp0) pccard. Speeds vary from 1 megabit to
theoretically 2 megabits (roughly T1 in speed).
The card has three fundamental hardware units, a so-called PSA or programmable
storage area, a radio modem, and a ethernet lan controller.
The latter component is the ancient (and not very honorable) Intel 82586
ethernet chip. Fundamentally it appears to the operating system as an
ethernet system, and speaks IEEE MAC addresses. The radio modem simply
translates ethernet packets to/from radio packets, that are either at 2.4
GHz or 915 MHz depending on the radio modem. It supports a collision
avoidance scheme. The lan controller supports promiscuous mode, broadcast,
and multicasting (although there is a glitch in the latter). "It
thinks it is ethernet".
How it is used depends on the kind of antennae deployed with it. Point
to point applications are possible as are ethernet-like lan use. The
vendor ships an omni-directional antennae that works in the vicinity of
400 feet (indoors). Point to point antennae can be purchased that will
go miles.
The card can either be initialized with the vendor supplied DOS setup
software. Typically minimally an IRQ, port, and Network ID must be supplied.
Michael Smith's wlconfig(8) utility can now be used to do this
work from the UNIX side. The card is "not" plug and play. The network
id controls whether one set of cards can hear another. If different,
cards will read physical packets, but they will be discarded by the radio
modem.
In addition to the config utility, there are several sysctl switches that
can be used to modify runtime parameters. The sysctl(8) variables are as
follows:
machdep.wl_xmit_delay <useconds> This variable will cause the driver to
insert a delay on transmit. 250 is the default. The delay should probably
be a bit longer on faster cpus and less on slower cpus. It exists
because the 82586 was not designed to work with Pentium-speed cpu systems
and if overdriven will have copious xmit side errors.
machdep.wl_ignore_nwid <0 | 1> This switch defaults to 0; i.e., the nwid
is not ignored. It can be set to 1 to cause the nwid to not be used.
This may be useful when the device is in promiscuous mode as one can
watch for all packets and ignore nwid differences.
machdep.wl_xmit_watch <milliseconds> This switch is not currently useful.
machdep.wl_gather_snr <milliseconds> This switch is not currently useful.
There is also a signal strength cache in the driver. It may be interrogated
with wlconfig(8). Incoming packets are checked for certain hardware
radio-modem values including signal strength, silence, and quality,
which range fro 0..63, 0..63, and 0..15 respectively. Thus one can read
out signal strenth values to see how close/far peer nodes are. The signal
strength cache is indexed by sender MAC address. There are two
sysctls that change how it filters packets. Both are on by default.
machdep.wl_wlcache_mcastonly <0 | 1> By default this switch is on. It
forces the cache to filter out unicast packets. Only broadcast or multicast
packets are accepted.
machdep.wl_wlcache_iponly <0 | 1> By default this switch is on. It
forces the driver to discard non-IP packets and also stores the IP src
address. ARP packets are ignored, as are any other network protocol barring
IPv4 packets.
The 82586 has numerous defects. It may experience transmit-side errors
when modern faster cpus send packets at it faster than it can handle.
The driver (and probably the chip) does not support an all multicast
mode. As a result, it can be used with applications like mrouted(8), but
it must go into promiscuous mode for that to work. The driver is slow to
change modes from "normal" to promiscuous mode, presumably due to delays
in the configuration code.
sysctl(8), wlconfig(8)
http://www.wavelan.com
The wl driver was written by Anders Klemets (thousands of years ago?) and
appears to be based on an even older Intel 82586 driver. The 82586 controller
was one of the first (if not the first?) integrated lan controller
on the block. That does not mean it was the best either. Anders
ported and or created a driver for the ISA wavelan and PCCARD wavelan
system too (wlp). Robert T. Morris, Jr. ported the Mach drivers to BSDI.
Jim Binkley ported them to FreeBSD 2.1. Michael Smith ported the wl
driver only to 2.2.2. Jim and Michael have been maintaining them. The
current state of the driver is NOT ANYONE'S FAULT. Thanks to Bernie
Doehner and Robert Buaas for contributions.
Too numerous to mention. See above.
FreeBSD 5.2.1 July 7, 1997 FreeBSD 5.2.1 [ Back ] | 