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Groups > comp.arch.embedded > #28838

Re: High packet rate ethernet with LwIP

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On Sat, 21 Sep 2019 19:00:16 +0200, David Brown
<david.brown@hesbynett.no> wrote:

>On 20/09/2019 18:27, Stef wrote:
>> For transportation of several high speed serial ports, we want to use a
>> serial over ethernet approach. At a minimum I need to transfer four ports
>> with 512 byte packets that come in every 40 ms at 2 Mbps.
>
>If you can consider USB instead of Ethernet, an FTDI 4232H chip will 
>handle 4 ports at 3 Mbps without trouble.
>
>But there are no limits in LWIP speed for what you need.  I have run a 
>board with a Modbus TCP/IP server handling 6 simultaneous connections 
>each with a transaction (request and reply) every millisecond - far more 
>packets than you need here.

That is essentially a half duplex environment with inherit flow
control. So if there is some congestion issues, it will clear sooner
or later.

The OP did not specify if those 2 Mbit/s streams had some kind of flow
control. If not, a congestion problem could cause an overflow and
possibly lockup.

Anyway, I did not notice that the packets came with such low duty
cycle, so even a 10baseT connections should be able to handle four
streams even with TCP/IP  even with some retransmissions, provided
that a missed frame is reacted upon in less than 40 ms.

>
>Your problem might be limiting parameters in the LWIP configuration, or 
>it might be in the basic structure of the code.  You can try increasing 
>configuration parameters to see if it helps.  You can also enable 
>statistics for LWIP, which can give you a clue - if you are getting 
>something on the failure counters, that will let you know what you need 
>to increase.
>
>Another poster suggested using WireShark to see the traffic - that is 
>definitely a useful tool.
>
>> 
>> Search for a ready to use (for test at least) device has turned up nothing.
>> Standard devices usually go up to 230 kbps, some to 1 Mbps. Most faster
>> ones are single port only. And it should be a small device, embeddable,
>> logic level is all that is needed. If anyone knows of a usable device...
>> 
>> Since the board that this is on incorparates an ethernet capable controller
>> (LPC4088) that has not that much work to do richt now, I thought it should
>> be possible to add ethernet to it.
>> 
>> For testing I got an LPC4088 demo board with ethernet interface and got
>> LwIP running on it (stand alone, no OS).
>> 
>> Got it working OK to simulate 4 ports sending slow data to 4 TCP ports
>> that can be opened with a PC terminal program.
>> 
>> But when I turn up the data volume and packet rate, it stops working.
>> In some cases stuck in the hard fault handler, in other cases in a
>> timed waiting loop in the LwIP stack.
>> 
>> At this moment it is running fine with 2 ports open and a 512 byte packet
>> every 100 ms on each. When I increase the speed to 50 ms, it stops after
>> a while.
>> 
>> I have no previous experience with LwIP so where to start looking?
>> - First of all does it sound feasable over a 100 Mbit ethernet
>>    connection using TCP?
>> - What can be tuned in LwIP to improve this?
>>    I have already increased PBUF_POOL_SIZE from default 7 to 64 and
>>    MEM_SIZE from 12k to 32k
>> 
>> 

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Thread

High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-20 18:27 +0200
  Re: High packet rate ethernet with LwIP upsidedown@downunder.com - 2019-09-20 21:20 +0300
    Re: High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-23 10:37 +0200
      Re: High packet rate ethernet with LwIP Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2019-09-23 14:08 +0300
      Re: High packet rate ethernet with LwIP Richard Damon <Richard@Damon-Family.org> - 2019-09-23 07:13 -0400
        Re: High packet rate ethernet with LwIP Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2019-09-23 18:55 +0300
      Re: High packet rate ethernet with LwIP David Brown <david.brown@hesbynett.no> - 2019-09-23 14:04 +0200
        Re: High packet rate ethernet with LwIP Dimiter_Popoff <dp@tgi-sci.com> - 2019-09-23 17:03 +0300
          Re: High packet rate ethernet with LwIP David Brown <david.brown@hesbynett.no> - 2019-09-23 18:37 +0200
            Re: High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-24 14:22 +0200
              Re: High packet rate ethernet with LwIP upsidedown@downunder.com - 2019-09-25 07:55 +0300
                Re: High packet rate ethernet with LwIP David Brown <david.brown@hesbynett.no> - 2019-09-25 09:51 +0200
                Re: High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-25 16:03 +0200
                Re: High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-25 11:59 +0200
                Re: High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-25 13:16 +0200
              Re: High packet rate ethernet with LwIP David Brown <david.brown@hesbynett.no> - 2019-09-25 09:42 +0200
                Re: High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-25 13:41 +0200
                Re: High packet rate ethernet with LwIP David Brown <david.brown@hesbynett.no> - 2019-09-25 14:10 +0200
                Re: High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-25 15:22 +0200
      Re: High packet rate ethernet with LwIP upsidedown@downunder.com - 2019-09-23 22:26 +0300
        Re: High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-23 22:16 +0200
          Re: High packet rate ethernet with LwIP David Brown <david.brown@hesbynett.no> - 2019-09-23 23:08 +0200
  Re: High packet rate ethernet with LwIP Joe Chisolm <jchisolm6@earthlink.net> - 2019-09-20 13:44 -0500
    Re: High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-23 10:46 +0200
  Re: High packet rate ethernet with LwIP David Brown <david.brown@hesbynett.no> - 2019-09-21 19:00 +0200
    Re: High packet rate ethernet with LwIP upsidedown@downunder.com - 2019-09-22 00:01 +0300
      Re: High packet rate ethernet with LwIP David Brown <david.brown@hesbynett.no> - 2019-09-22 09:06 +0200
        Re: High packet rate ethernet with LwIP upsidedown@downunder.com - 2019-09-22 11:29 +0300
          Re: High packet rate ethernet with LwIP David Brown <david.brown@hesbynett.no> - 2019-09-22 23:24 +0200
        Re: High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-23 11:10 +0200
    Re: High packet rate ethernet with LwIP Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2019-09-23 11:03 +0200

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