Subject: Re: ifconfig for wireless LAN
To: Atsushi Onoe <onoe@sm.sony.co.jp>
From: Bill Sommerfeld <sommerfeld@orchard.arlington.ma.us>
List: tech-net
Date: 03/21/2000 22:08:07
> 1. "FH" and "DS" cannot be set at all. It just show the type of
> PHY chip on the card, and printed at attaching the interface
> would be enough.
I'm not sure I agree here; I'd prefer to see this information
available through the system call interface. Also, Murphy's Law says
that if we change this, we'll discover N months later that someone's
built a dual-mode 802.11 card.
> 2. Bit rate is not necessarily specified for most cases.
> Both for infrastructure mode and ad-hoc (IBSS) mode,
> spec says that the PHY with multirate support MUST use
> basic rate for multicast/broadcast and control frames,
> and MUST NOT transmit at a higher rate without prior knowledge
> of destination's supported rate, which are shown by beacon
> frames or association requests.
agreed. it appears as if 802.11 can operate with multiple bit rates
simultaneously (a BSS -- the lower-level RF subnet concept in 802.11
-- has a *set* of supported rates which can all be in use, not a
single rate). It may be desirable to have a knob to disable/enable
rates supported by a particular card (in the event that there are
interoperability problems at certain rates), but I don't have much
experience with multi-rate 802.11 networks..
> 3. The infrastructure mode and the ad-hoc mode are clearly different
> and cannot interoperable each other. So they cannot be "media
> options" but mutually exclusive "media types".
well, "full duplex" and "half duplex" for ethernet can't interoperate
either. i'm not sure how this follows.
> And there are some more options to be defined for wireless LAN.
> create-ibss Create its own IBSS and announce it when it fails
> to find or join existing IBSS.
> Only valid for the adhoc media type.
> Note that isolated two node with this option
> cannot talk to eath other even if they come closer
> again.
well, i don't have a copy of the wi hardware specs, but the awi
microcode supports a "background scan" mode which might be convinced
to let an IBSS leader scan for other IBSS's within range.
> no-bssid Do not use bssid nor beacons at all. It is just
> same as adhoc mode of WaveLAN (wi(4)).
> Only valid for the adhoc media type.
right, non-standard mode.
> wep Enables WEP (Wired Equivalent Privacy). It requires
> WEP encryption to communicate others.
yup.
> power-mgmt Enables power management capability. Only available
> for infrastructure media type and it requires
> additional support by access points.
yup. there may be some interop issues here as well.. I may need to
tweak various parameters on the basestation side, but turning on power
management on the wi* caused it to fail to interop with a baystack 660
DS basestation..
> Possibly more to be defined somewhere:
> desired ESSID currently can be specified by the "nwid" parameter of
> ifconfig(8). Empty string ('') means wildcard
> ESSID which allow to connect any access points.
> created ESSID used for "create-ibss". It may be the same string
> with desired ESSID but it should not be empty.
I'm not sure these two really need to be distinct.
> WEP key used for "wep" encryption/decryption.
The protocol allows for up to four different WEP keys with different
key id's; there should also be a "key id to use on transmits".
> channel/pattern used for "create-ibss" to determine the radio
> frequency (DS) or hopping pattern (FH) to be used
> to create IBSS. Also used for "no-bssid".
right..
- Bill