why retransmisson of TCP handshake

asked 2023-06-23 16:20:59 +0000

matthias gravatar image

updated 2023-06-23 16:50:14 +0000


I am new to wireshark and use wire on my network and capture traffic via mikrotik router "packet sniffer" and the result is my question here , in TCP handshake there is an retransmission and for all steps of the setup and i know that the Speed of my network card on my dell laptop is not 100Mb but the switch TP link is GB and the TPlink switch is managed switch. My router hace QoS and GB ports ad i see ICMP packet drop and fine tuning the max limit up from 3M to 5M that seems overkill but again i do not know the reccomended values.

where do i start ?, is it possibe to have "no retransmissions" in TCP handshake at al ? if so what is normal amount of retransmisson.

additiona linformation: when i run speedtest by ookla the download speed start low 20Mb and slowely ramps upp to 300Mb but the upload test goes directly up to 300Mb, use RB4011 router and switch is connected to the same switch chip as the ISP are and QoS is present and i am fine tuning the parameters, uses: ICM(1st), DNS(2nd), WEB(6th), VoIP(2nd), WEBEX(3rd), Email (4th)and REST(7th, remaining traffic of less interest).

Thank you

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TCP retransmissions in the 3-way handshake can happen due to server congestion, network congestion, or packet drops. Did you try removing the QOS policy?

BigFatCat gravatar imageBigFatCat ( 2023-06-24 09:58:51 +0000 )edit

Can you share us atria?

Christian_R gravatar imageChristian_R ( 2023-06-25 19:25:10 +0000 )edit

It seems my laptop sends syn and 0.000016s later also sends tcp retransmission to ip

Server Responde with syn ack at 0.253xxs AND syn ack retransmisson 0.000020s later back to my laptop.

sory but unable to incliude evidence since i do not have 60 points in this forum to be able to attach an image.

matthias gravatar imagematthias ( 2023-07-03 15:16:18 +0000 )edit