tcp retransmission

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emanueletrapani
Contributor III

hi, i use mqx 4.2, cw 10.6 and frmk64f.

when i use this board for a comunication on ethernet lan i see that there are a lot of retransmission packets: about 30% of transmitted packet. i try to write a simple application that send several packets on lan from my board to my pc at hercules application. while it is transfering i use wireshark to see the traffic on the lan. my question is:

- is it normal to have about 30% of ethernet traffic composed by [TCP RETRANSMISSION] packets?

- there is a way to avoid it?

thanks

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Carlos_Musich
NXP Employee
NXP Employee

Hi Emanuele,

please set _TCP_rto_min value to 250 just after RTCS_create().

error = RTCS_create();

_TCP_rto_min = 250;

This issue is related to Retransmission's Time Out (RTO) and Retransmission-Time Trip (RTT). I will write a small document explaining the details.


Regards,
Carlos

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emanueletrapani
Contributor III

hi carlos,

i did another test but i see always the retransmission packets. i do this:

i create a new bsp cloned from frdmk64f not modified bsp

i created a new projet mqx4.2 starting from example: eth_to_serial

i replace the demo.c file with the same file i sent you

i set the bsp with ENABLE_ITTYA and ENABLE_IO_SUBSYSTEM

i compiled bsp, psp and rtcs lib.

i compiled the code

i run on my device and i see always the retransmission packet.

is it possible?

are you using a not modified version of frdmk64f bsp?

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emanueletrapani
Contributor III

hi,

it appears strange to me but i will do some other tests.

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