LwI 2.1.2: Cant ping data greater than 1472 bytes

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LwI 2.1.2: Cant ping data greater than 1472 bytes

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Contributor III

Hello,

I am using s32K148. I am running the lwIP example given in s32DesignStudio SDK. I have a problem which I want to share. I am trying to ping my controller with data greater than 1472 bytes but I am not getting any response. What should I do. Also If there is a lot of traffic on my ethernet port my board hangs and gets stuck into Default ISR. 

Waiting for your reply.

Regards,

Saad.

2 Replies

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NXP Employee
NXP Employee

Hello Saad,

Standard Ethernet frame is 1518 bytes long. There are 14 bytes for Layer 2 header (Source and destination MAC + type) + 4 bytes for CRC check. So, 1500 bytes remains for IPv4 packet itself.

IPv4 packet header has 16 bytes, so, 1484 bytes remains. And if you use TCP or UDP protocol on transport layer, there is also some header (UDP header is 4 bytes long, TCP header is 16 bytes long), so 1472 bytes for data itself seems to be correct.

Typically frames greater then 1518 bytes (Giant frames) are discarded by device, because they need some special implementation for handling.

Regards,

Martin

5 Views
Contributor III

Ok Martin,

Thanks.

Do you have any idea why my board gets stuck in the 'Default ISR; mode as I have mentioned this in my question too.

Plus, is there any chance you can port FNET with your  s32 design studio SDK. Reason is there is no little or no help available regarding lwIP.  

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