FW: [MLB-WIRELESS] So how does this routing bit work?

[Bryce Letcher]

Guys,
Thx for getting the system up again.
And now on with the dance  :)


ben> -----Original Message-----
ben> From: Ben Anderson [mailto:a_neb at optushome.com.au]
ben> Sent: Thursday, 21 March 2002 14:12
ben> To: Bryce Letcher; melbwireless at wireless.org.au
ben> Subject: Re: [MLB-WIRELESS] So how does this routing bit work?

<snip>

ben>
ben> That "knowing" is done by the ARP cache of ethernet MAC's.  A
ben> router and a
ben> bridge are different technologies.  One does the
ben> re-transmission decision at
ben> the data-link layer (layer 2 OSI), and the other does the
ben> re-transmission at
ben> the network layer (layer 3 OSI).  The retransmission done at layer 2
ben> effectivly makes that look like everything is part of the same network
ben> segment to layer 3 and above, whereas when the layer 3 routing
ben> occurs, it's
ben> only layer 4 and above that appears to be part of the same network.

OSI?? I thought we were talking TCP/IP. The models are totally different and
there is no correlation between the 7 layer OSI model and the 4 layer TCP/IP
model.

<snip>

ben>
ben> Unless there's repeating done, it never will.  Most of the discussions
ben> previously have been about getting this done at layer 3 OSI.
ben> I'm designing a method that should either shim, or replace
ben> layer2/3 OSI....
ben> And hopefully this solution should solve a lot of the issues you point
ben> out...  Certainly, it's not finished, and it's not a short
ben> term project.

This is a massive project, and I foresee the need to have firmware written
to drive this concept, not just some application layer stuff. That implies
cooperation from the RF card manufacturers!!

<snip>

ben>
ben> Not really a big problem.  Any network card with a diversity
ben> antenna could
ben> for example have two antennas off the one device, when the one device
ben> transmits, both antennas get the signal (rx is turned off)..

??? Diversity is a method of using multiple antennas to improve QoS in a
poor signal situation, particularly when fading occurs. I don't understand
what you are attempting to do with the two antennas.



ben> badda bing, it
ben> works.
ben> Alternativly, if there is actually 2 real nodes, just have it
ben> so that they
ben> can't see each other, either by having a different hopping
ben> sequence on the
ben> same channel, or just using a different channel, then there's
ben> no risk of a
ben> loop as they're not receiving each others transmissions  (well...  they
ben> could interfere, depending on the quality of hte bandpass
ben> filters in the
ben> device, but due to the different hop sequences, it won't do
ben> anything but
ben> make traffic on the other interface harder to hear)

With more than 15 yrs experience in radio systems I remain totally
unconvinced.

<snip>

ben> Hopefully my comments sort this out for you...

eerrrrr no. You may think I'm just sceptical, but I have serious doubts that
this is the right approach. I think the groups would be much better off
utilising an "out of box" solution. Shouldn't we be looking to the US and
Europe for working systems that we can leverage?

rgds,
Bryce