IP: more on Intel wants to turn PCs into wireless LAN accesspoints

[Dave Farber <dave () farber net>]

------ Forwarded Message
From: "Christian Huitema" <huitema () windows microsoft com>
Date: Sat, 13 Apr 2002 11:23:23 -0700
To: <farber () cis upenn edu>
Subject: RE: more on  Intel wants to turn PCs into wireless LAN
accesspoints 

There are two ways to use 802.11 wireless cards on a PC today:
infrastructure mode, i.e. connected to a base station, and ad hoc mode,
i.e. a direct connection between two PC. Both modes are supported in
Windows XP. Windows XP also include two networking components that can
be used in wireless networks: the Internet Connection Sharing software
which is a NAT, and allows you to share an Internet connection, and the
bridge, which is an implementation of the IEEE 802 specification,
including the spanning tree algorithm. The  bridge also include
proprietary technology to enable bridging on networks where it is not
possible to place the network interface card in promiscuous mode, such
as IEEE 1394 buses or 802.11. It is definitely possible to use two
Windows XP laptops in the configuration described by Christopher Davis.
One laptop will have a modem connection and enable ICS; the 802.11
connection will be used in "ad hoc" mode. In fact, some of my colleagues
have donated laptops for a similar usage at the UW Hospital extended
care maternity ward.

The problem with the access point functionality is strictly a MAC issue.
The access point implements a slightly different MAC algorithm than a
plain "client" card. To use a PC as an access point (by opposition to ad
hoc mode) requires either rewriting the firmware on the card, or using a
card that only implements the radio procedures and implementing the
access point MAC functions in the driver. Both are possible; people who
speak of a "software access point" typically refer to the second
approach.

-- Christian Huitema



------ End of Forwarded Message

For archives see:
http://www.interesting-people.org/archives/interesting-people/