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<P><FONT SIZE=2 FACE="Arial">Hi,</FONT>
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<P><FONT SIZE=2 FACE="Arial">We are developing an application which is based on a 802.11 wireless backbone</FONT>
<BR><FONT SIZE=2 FACE="Arial">as described below:</FONT>
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<P><FONT SIZE=2 FACE="Arial"> 0(------------)0(------------)0(-- . . . --)0--------[control center]</FONT>
<BR><FONT SIZE=2 FACE="Arial"> node 1 node 2 node 3 node N</FONT>
<BR><FONT SIZE=2 FACE="Arial"> data source data destionation</FONT>
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<P><FONT SIZE=2 FACE="Arial">The nodes are based on SBC (single board computer) running linux. Each node will</FONT>
<BR><FONT SIZE=2 FACE="Arial">run 2 802.11 radio lan cards and each card will be connected to one branch of the backbone.</FONT>
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<P><FONT SIZE=2 FACE="Arial">The backbone will be used to transmit MULTIMEDIA (image, voice) contents.</FONT>
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<P><FONT SIZE=2 FACE="Arial">At first, I thought There were 2 options to accomplish this:</FONT>
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<P><FONT SIZE=2 FACE="Arial">1) Using N routers. Each node pair forming a network and constructing</FONT>
<BR><FONT SIZE=2 FACE="Arial"> routing rules on each node of the backbone.</FONT>
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<P><FONT SIZE=2 FACE="Arial">2) Replacing each node's couple wavelan card by a logical adapter forming </FONT>
<BR><FONT SIZE=2 FACE="Arial"> bridge. So, each node of the backbone will be on the same network.</FONT>
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<P><FONT SIZE=2 FACE="Arial">Constraints on the above options where found:</FONT>
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<P><FONT SIZE=2 FACE="Arial">1) The number of Wireless routers on a network is limited to a maximum of 3. More than 3 hopes will lead to a timeout of ACK packages in level 2. This will collapse the whole </FONT></P>
<P><FONT SIZE=2 FACE="Arial">network performance.</FONT>
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<P><FONT SIZE=2 FACE="Arial">2) 802.11 protocol has some architectural differences from standard ethernet protocol. Standard bridge setup on linux I have tried have failed.</FONT></P>
<P><FONT SIZE=2 FACE="Arial">Some research on the Internet lead me to some possible alternatives:</FONT>
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<P><FONT SIZE=2 FACE="Arial">1) On some forum emails I have read that some firmware modifications could be done but will demand a "very strong 802.11 protocol knowledge". </FONT></P>
<P><FONT SIZE=2 FACE="Arial">2) Using vtun tunnel. Further details on </FONT><A HREF="http://vtun.sourceforge.net"><U><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">http://vtun.sourceforge.net</FONT></U></A>
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<P><FONT SIZE=2 FACE="Arial">3) Creating a bridge using cards having the prism chipset onboard (manufactured by Harris Intersil). There are drivers for those cards available at </FONT><A HREF="www.linux-wlan.com"><U><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">www.linux-wlan.com</FONT></U></A><FONT SIZE=2 FACE="Arial"> (which is the website from Absoval), and I found a mail that says that there is the necessary firmware and an upload tool available for Linux to the public. If you need additional features of an access point you should also talk to Absoval. </FONT></P>
<P><FONT SIZE=2 FACE="Arial">4) Vladimir Ivaschenko has created parprouted, a daemon for transparent IP (Layer 3) proxy ARP bridging. This allow to do "IP bridging" on any 802.11 card (instead of MAC bridging). </FONT><A HREF="http://www.hazard.maks.net/"><U><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">http://www.hazard.maks.net/</FONT></U></A></P>
<P><FONT SIZE=2 FACE="Arial">5) InfoTech was developing a 802.11 software stack for Linux, including the Access Point functionality. </FONT>
<BR><A HREF="http://www.instant802.com/openap1.htm"><U><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">http://www.instant802.com/openap1.htm</FONT></U></A>
<BR><A HREF="http://opensource.instant802.com/what_is_openap.php"><U><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">http://opensource.instant802.com/what_is_openap.php</FONT></U></A><FONT SIZE=2 FACE="Arial"> (Opensource version)</FONT>
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<P><FONT SIZE=2 FACE="Arial">6) Jouni Malinen has developed a driver for the PrismII cards supporting Host AP mode and bridging.</FONT>
<BR><A HREF="http://hostap.epitest.fi/"><U><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">http://hostap.epitest.fi/</FONT></U></A>
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<P><FONT SIZE=2 FACE="Arial">We demand some urgent solution for our backbone solution. </FONT>
<BR><FONT SIZE=2 FACE="Arial">Any comments, suggestions or advice will be very appreciated</FONT>
<BR><FONT SIZE=2 FACE="Arial">and useful.</FONT>
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<P><FONT SIZE=2 FACE="Arial">Regards,</FONT>
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<P><FONT SIZE=2 FACE="Arial">Andre Moutinho</FONT>
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