TX error due to colision or erroneous TX

[David Gibson]

On Wed, Feb 27, 2002 at 12:30:43PM +1100, Bruce Janson wrote:
>     From wireless-admin at lists.samba.org Wed Feb 27 12:16:31 2002
>     ...
>     From: David Gibson <david at gibson.dropbear.id.au>
>     ...
>     On Tue, Feb 26, 2002 at 07:09:00PM -0500, Amit Jain wrote:
>     ...
>     > 
>     > Just to check whats happening, I configured my laptop to run in Ad-hoc
>     > mode with just it as the node in the network. And I ran 'ping' to some
>     > hosts and obviously the ping reprted  "Destination unreachable" since the
>     > network has only one node.
>     
>     Specifically "destination unreachable" means that your machine
>     received no reply to its ARP query.
>     
>     > But the surprising thing is that card raised the interrupts corresponding
>     > to HERMES_EV_TX and not HERMES_EV_TXEXC. ??
>     > 
>     > Since there are no other stations in the n/w, it is impossible for my
>     > laptop to recevie an ACK for the transmitted packet. So if TX is
>     > based on 802.11 ACK protocl, then in this cse function handler
>     > corresponding to EV_TXC  should have been called. I do not understand why
>     > I am getting "Successful transmission signal" as indicated by EV_TX.
>     > (in 802.11 succesfull packet trnasmission means that the packet was
>     > trnamitted correctly and subsequent ACK received correctly)
>     
>     I think this must be because the ARP is failing.  ARP requests are
>     broadcast packets, and for obvious reasons these wouldn't be ACKed.
>     ...
> 
> David,
>   Well, not entirely obvious.  If I didn't know in detail how an 802.11 WAN
> worked (which I don't, and when did WAN stop meaning Wide Area Network???),

Where di you get the term "WAN" from.  WLAN if the term usually used.

> I could imagine an asymmetric network architecture where nominated
> central locations (access points?) did acknowledge ARP packets as part
> of their provision of a synthetic carrier sense.  But I am perfectly
> happy to take your word for it. :-)

But this is an ad-hoc network.  Actually I'm not sure what the details
of the correct behaviour are here - and I don't feel like ploughing
through the standard to work out at the moment - but I imagine that's
what's making the difference.

-- 
David Gibson			| For every complex problem there is a
david at gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.  -- H.L. Mencken
http://www.ozlabs.org/people/dgibson