First, and very quick, impressions. This approach requires not so minor change in WiFi driver: - normally, in the infrastructure network, multicasts are transmitted via Access Point. Client transmit its multicast datagram as an unicast, directed to AP, and then AP retransmits is as a multicast to everybody - To change this normal behavior, driver changes are required. I'm not even sure that all existing 802.11 chipsets can in principle support this mode. The decision how to transmit broadcast packet may be implemented in the MAC firmware, not in the driver. - By default, if encryption is enabled, non-encrypted packets will be dropped on reception. Changing this behavior requires driver patch, and, even worse, it opens station to the unwanted unencrypted traffic. - Usually multicasts are transmitted at very low transmit rate (so everybody will have chance to receive them). I'm not sure that for every chipset this is possible to change it in the driver. - All participating stations must disable 802.11 powersaving. 802.11 power saving depends on multicast queuing implemented by Access Point.
The requirement to patch the driver may make this technology very difficult to implement on MS Windows, where driver sources are generally hard to obtain. If there is interest, I can propose changes to the approach, which will allow Windows stations with unpatched drivers at least to receive traffic from such a network (transmission and feedback will not be possible without driver modifications). Andy Green wrote: > Hi folks - > > Sergeui Osokine suggested posting here about a quite unusual network > concept I have started working on. > > The basic concept is that all those machines you see around you on your > wifi applet or iwlist wlan0 scan could participate together to form a > large and fast, if patchy network completely outside the Internet, using > addressless unencrypted broadcast packets, at the same time they remain > associated and using crypto for their internal traffic as usual. > > I have written up the concept here: > > http://penumbra.warmcat.com > > The state at the moment is I am working on two Linux wifi drivers, for > zd1211rw and ipw3945 to add the Penumbra packet transfer stuff as a > proof of concept, and that the usermode daemon SSL and upload stuff is > done and under GPL. So it is quite early days but there is progress. > > The main questions remaining are about how to discover content and route > it around in such a strange network, where there are no addresses or > other identifying information about the stations, and anyone can inject > content anonymously. > > I am very interested to hear peoples' ideas or questions! > > -Andy _______________________________________________ p2p-hackers mailing list [email protected] http://lists.zooko.com/mailman/listinfo/p2p-hackers
