On Thu, Dec 16, 2010 at 8:24 AM, Mohan R <mohan@mro-tek.com> wrote:
Hi Ashwin,

I have verified that I am not dropping any packets.
It is just that occasionally packets are reordered.

Statistics on the wired or the wireless interface do not report any lost or
dropped packets


-----Original Message-----
From: Ashwin [mailto:ashwin.lists@gmail.com]
Sent: Thursday, December 16, 2010 4:55 PM
To: madwifi-users@lists.sourceforge.net
Subject: Re: [Madwifi-users] [SPAM] Madwifi v0.9.4 latest release: Frames
transmitted out of sequence

Hi Mohan,

As it seems, the issue is more with the setup that you have. Maybe you
can try tweaking (increasing) buffers settings under sysctl ?

Could also be an issue with the "wired" interface with low buffers (in
the hardware itself). Use a very high quality ethernet card.

with Regards,

On 12/16/2010 01:21 PM, Mohan R wrote:
> Hi Dennis&  Wayne,
> Thanks for your response.
> In my application I receive UDP/IPV4 packets from a wired interface. I
> no control on this protocol.
> My application has a peek of the data in frame, collects some statistics
> just forwards the frame over the wireless interface using dev_queue_xmit.
> One of the nodes is configured as AP&  the other as Station. There is a
> sequence number associated with the payload. That is how I know that the
> packets are out of order when I receive them at the far end.
> I have Linux version 2.6.18 running on MIPS platform with AR5414A chipset
> based mini-PCI.
> When I started work on this application, I had examined the packet
> from the wired i/f. They seemed to be in order. I will verify this once
> again.
> My question now is are there any circumstances under which madwifi or
> dev_queue_xmit can reorder packets ?
> Regards
> R.Mohan
> -----Original Message-----
> From: Wayne Johnson [mailto:wayne@zk.com]
> Sent: Wednesday, December 15, 2010 11:52 PM
> To: Dennis Borgmann; MOHAN.R.
> Cc: madwifi-users@lists.sourceforge.net
> Subject: RE: [Madwifi-users] [SPAM] Madwifi v0.9.4 latest release: Frames
> transmitted out of sequence
>> -----Original Message-----
>> From: Dennis Borgmann [mailto:dennis.borgmann@googlemail.com]
>> Sent: Wednesday, December 15, 2010 5:39 AM
>> To: MOHAN.R.
>> Cc: madwifi-users@lists.sourceforge.net
>> Subject: Re: [Madwifi-users] [SPAM] Madwifi v0.9.4 latest release:
>> Frames transmitted out of sequence
>> Hi Mohan!
>> Maybe this is not an issue of madwifi, but an issue of you IP
> protocol?
>> Are you using UDP? If so, try TCP since it guarantees the sequence of
>> packet transmission.
>> HTH,
>> Dennis Borgmann
> I don't think your statement is necessarily correct. With TCP, data
> leaving the transport layer and entering the application layer is
> guaranteed to be in order but packets can still arrive on the network
> layer out of order.
> It has been some time since I have done a lot of TCP/IP work but it is
> my understanding the out of order typically not a problem unless there
> is routing going on.
>> MOHAN.R. schrieb:
>>> Dear All,
>>> Occasionally I find that frames are being transmitted out of
> sequence
>> by
>>> both AP as well as Station.
>>> This is not desirable for my application.
>>> Can anyone tell me why this happens and how to ensure that frames
> are
>>> always sent in sequence.
> Without making quite a few assumptions it's not possible to even
> understand what you are asking here. A lot more detail is required. How
> are you sending the packets? How are you determining they are out of
> order? What hardware and software are you using on both ends? What are
> you trying to do?
> I don't want you to take this the wrong way, I am still trying to be
> helpful. Even though engineers are known for their literary skills ;-),
> answering questions still takes quite a bit of effort. I have found that
> most people try hard to be helpful when they can see that you are trying
> hard to figure it out. Most likely you are working very hard to figure
> out your problem but your email does not convey that and will probably
> be ignored by the people who (unlike me) can be most helpful.
> Wayne


Can you please test UDP performance of your system with iperf?  iperf -s -u -i 1 will launch a test server, and iperf -c <address of server> -b 2M -i 1 will launch a client sending a 2Mbps stream to the server (adjust throughput as you see fit).  The server will report statistics on dropped and out of order packets every second.  You can also adjust the packet size to more closely reflect what your application is doing.  I haven't seen more than the occasional out of order packet, and I'd like to see what a standard test tool reports.