TX error due to colision or erroneous TX

[Amit Jain]

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.

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)

Kindly help, as my whole experimentation are based on this event handling.

I did this experiment in my apartment (rather than lab) so I was quite
sure thre no effects due to other wireless stations. Below is the
information regarding system paramaters.

iwconfig output:
	eth1: IEEE 802.11-DS ESSID:"JAS Network" Nockname:"sagar"
	      Frequency:2.457 Ghz  Sensitivity:1/3   Mode:Ad-Hoc
              Acces Point : 02:02:2D:4a:33:23
	      Bit Rate:2Mb/s RTS thr:off  Fragment thr: off
              Encryption Key:off
              Power Management:off
              LInk Quality:0 Signal:0 Noise Level:0
	      Rx invalid nwid:0 invalid crypt:0 invalid misc:0

Also, there was some strnage thing happening. when I was sding the pa kes
thru eth1 my loopback interface also showed increment in TX and RX ??



On Thu, 21 Feb 2002, David Gibson wrote:

> On Wed, Feb 20, 2002 at 04:47:17AM -0500, Amit Jain wrote:
> >
> > Thanks for your reply.
> >
> > Can you provide one more clarification.
> >
> > Since 802.11 protocol requires ACK for every TX packet that means card
> > waits for the ACK. So, does this mean that interrupt TX_EXC is based on a
> > timeout (smaller and different from tx_timeout, which detects h/w lockups
> > or missing interrupts)
>
> Yes.
>
> --
> 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
>
>