Author Topic: 2 packets send for 1 ack??  (Read 4278 times)

mconnell

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2 packets send for 1 ack??
« on: July 10, 2007, 06:54:52 PM »
I am monitoring data sent from the sbc65.  We see the data packet being sent, then the ACK, then we see another being sent that is a 0 data length packet.  So we send one valid packet and receive an ACK.  What is this extra packet being sent that is bogus?

OmarZ

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Re: 2 packets send for 1 ack??
« Reply #1 on: July 11, 2007, 12:06:55 AM »
Which realease of sbc65 are you using? 3.04,3.05,3.06?
In my experience 3.04 is the "clean and clear one"; other versions has got a different working mode. If you try to send from board long tcp messages you will immediately see differences.
http://forum.modtronix.com/index.php?topic=592.msg1794#msg1794

modtro2

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Re: 2 packets send for 1 ack??
« Reply #2 on: July 11, 2007, 05:03:45 PM »
Hello Omar

I thought we resolved the issue about the messages longer than 970 bytes long ago already. The fact is that V3.06 is very stable, and can send messages longer than 970 bytes. Of course it can, how else do you explain all the files sent by the HTTP server. Most of these files are much longer than 970 bytes, and are send via standard TCP streams. You were using the stack in the wrong way, that is why it did not send messages longer than 970 bytes. It was just a variation in the code in V3.04 that tollerated the wrong method used to send long messages. Please refer to the following post, in which you acknoledged that you have resolved the problem of sending long messages with V3.06.
http://forum.modtronix.com/index.php?topic=592.15

Our current online web server, which gets "abbused" daily by 1000s of hits, has been running for months now without a reset. The only thing that causes it to go offline each couple of days (weeks) is when the Billion router it is connected to locks up. The online demo uses V3.06, and is at http://www.modtronix.com/links/onlinemxws. By viewing this page you will have a couple of files sent to your PC that are much longer than 970 bytes. Take a look in Ethereal, and you will see.

mconnell

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Re: 2 packets send for 1 ack??
« Reply #3 on: July 11, 2007, 06:06:03 PM »
The long packet problem was not my question.  We seem to be sending 2 packets out for every ACK received.  See below.

Can I ask you about a problem we are having with our IP stack.  We seem to be sending a version of our data twice.  We send a valid data packet from the SBC65 board that is being received by our server just fine.  Then we receive a proper ACK back from our server to the SBC65.  Then the SBC65 sends a shortened version of the origional data packet with 0 length for the data to our server.  Things are working however where is this extra packet coming from?  See example below.
 
Data from SBC to our server.
00 07 E9 23 AB F4 00 E0 52 CE B3 2C 08 00 45 00 00 88 A0 42 40 00 54 06 ED 0C 18 7E BB 35 C6 B1 FE BB 04 31 04 00 00 AC 73 D6 73 79 F3 23 50 18 04 00 67 A3 00 00 55 AA FE 0C B5 42 2A 2A 55 6E 52 65 67 2A 2A 32 30 39 B2 55 AA 01 08 B5 43 23 ED 87 E6 FD 00 00 40 46 55 AA 02 11 C5 29 23 ED 87 ED 87 00 00 00 00 00 00 00 00 ED 87 ED 87 0D 55 AA 04 07 B5 41 23 00 00 00 00 00 00 DD 55 AA 0B 11 C5 20 23 ED 87 E6 FD 00 00 00 00 00 07 00 BF 00 BF DB 00 26
Our data starts at 55 AA that is underlined
 
The server responds back with the ACK
00 E0 52 CE B3 2C 00 07 E9 23 AB F4 08 00 45 00 00 29 4E 6E 40 00 80 06 00 00 C6 B1 FE BB 18 7E BB 35 04 00 04 31 73 79 F3 23 00 AC 74 36 50 18 FC 30 99 3C 00 00 01
 
The SBC then sends this mysterious packet back to our server
00 07 E9 23 AB F4 00 E0 52 CE B3 2C 08 00 45 00 00 28 A0 43 40 00 54 06 ED 6B 18 7E BB 35 C6 B1 FE BB 04 31 04 00 00 AC 74 36 73 79 F3 24 50 10 04 00 2F 02 00 00 2F 00 00 00 00 00
We can not find where this is coming from.  It is not in our code.
 
This process repeats for every packet sent by the SBC65

modtro2

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Re: 2 packets send for 1 ack??
« Reply #4 on: July 11, 2007, 08:53:19 PM »
Can you please help me reproduce the reported condition. Have you modified the code, or is this happening when you request a HTTP page from the standard SBC65EC Web Server? If this is the case, please tell me what I must do to reproduce the condition.