[lwip-users] RE: lwip-users Digest, Vol 60, Issue 3

[Gary Olson]

Hi,
Thank You all for your very good input.  I was able to get my packet size up
to 2500 bytes which
Should be good for what I am trying to do.    My Xilinx board will only be
hooked to a PC so 
The extra long packets will not be affected by network components.  If
interested I have a thread
At Xilinx website you could take a look at.

http://forums.xilinx.com/xlnx/board/message?board.id=EDK&thread.id=4361

and there is a second thread I created earlier about PBUF length that is no
longer a problem since
I increased the size of my packets to 2500 bytes in UDP transfers.


Thanks,
  Gary Olson



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Today's Topics:

   1. Xilinx Board LWIP UDP Packet Length limitation (Gary Olson)
   2. Re: Xilinx Board LWIP UDP Packet Length limitation
      (address@hidden)
   3. RE: Xilinx Board LWIP UDP Packet Length limitation (Bill Auerbach)


----------------------------------------------------------------------

Message: 1
Date: Wed, 6 Aug 2008 13:37:36 -0400
From: "Gary Olson" <address@hidden>
Subject: [lwip-users] Xilinx Board LWIP UDP Packet Length limitation
To: <address@hidden>
Message-ID: <address@hidden>
Content-Type: text/plain; charset="us-ascii"

Hi,

  I am working with Xilinx EDK and LWIP I think it is version 1.2.   I am
able to use the uecho test to send UDP packets less that length 1460 bytes
or so. 

 But when I try to increase the UDP Packet length to 2000 it fails.  My
desire is to at least be able to send packets that are 

2500 bytes in length.  This is because I am trying to send  a whole packet
of data with the length of one packet to be about 2020 bytes maximum.

 

 

I tried increasing the TCP_MSS value from 1460 to 3000 (in the lwip software
settings).  This did not make it work however.

 

Does anyone know what I can do to send larger packets using LWIP.

 

Thank You,

  Gary Olson

 

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Message: 2
Date: Wed, 06 Aug 2008 22:33:24 +0200
From: "address@hidden" <address@hidden>
Subject: Re: [lwip-users] Xilinx Board LWIP UDP Packet Length
        limitation
To: Mailing list for lwIP users <address@hidden>
Message-ID: <address@hidden>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I don't have experience with ethernet packets bigger than1514 bytes, but 
I think the main limitations are:
- netif->mtu (you have to set this when initializing the netif)
- TCP_MSS (as you already have discovered)
- IP fragmentation: either turn it off (define IP_FRAG to 0) or set 
IP_FRAG_MAX_MTU higher than its default (1500)

there may be more though...

Simon



Gary Olson wrote:
>
> Hi,
>
>   I am working with Xilinx EDK and LWIP I think it is version 1.2.   I 
> am able to use the uecho test to send UDP packets less that length 
> 1460 bytes or so. 
>
>  But when I try to increase the UDP Packet length to 2000 it fails.  
> My desire is to at least be able to send packets that are
>
> 2500 bytes in length.  This is because I am trying to send  a whole 
> packet of data with the length of one packet to be about 2020 bytes 
> maximum.
>
>  
>
>  
>
> I tried increasing the TCP_MSS value from 1460 to 3000 (in the lwip 
> software settings).  This did not make it work however.
>
>  
>
> Does anyone know what I can do to send larger packets using LWIP.
>
>  
>
> Thank You,
>
>   Gary Olson
>
>  
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> lwip-users mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/lwip-users





------------------------------

Message: 3
Date: Wed, 6 Aug 2008 18:08:28 -0400
From: "Bill Auerbach" <address@hidden>
Subject: RE: [lwip-users] Xilinx Board LWIP UDP Packet Length
        limitation
To: "'Mailing list for lwIP users'" <address@hidden>
Message-ID: <address@hidden>
Content-Type: text/plain;       charset="us-ascii"

> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden On
> Behalf Of address@hidden
> Sent: Wednesday, August 06, 2008 4:33 PM
> To: Mailing list for lwIP users
> Subject: Re: [lwip-users] Xilinx Board LWIP UDP Packet Length
> limitation
> 
> I don't have experience with ethernet packets bigger than1514 bytes,
> but
> I think the main limitations are:
> - netif->mtu (you have to set this when initializing the netif)
> - TCP_MSS (as you already have discovered)
> - IP fragmentation: either turn it off (define IP_FRAG to 0) or set
> IP_FRAG_MAX_MTU higher than its default (1500)
> 
> there may be more though...

You have to be sure all devices on the switch are Jumbo Frame enabled too.

2 packets come in back to back within microseconds of each other.  I don't
really think there is any significant benefit to large frames.  In our
application using them improved bandwidth a negligible amount.  We don't
want network compatibility issues or requirements for Jumbo Frame supporting
hardware to be installed to work with our device, so we stuck with the
industry standard normal packet size.

Bill






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