---
title: "TCP spurious retransmission"
url: "https://maker.wiznet.io/forum/13984"
markdown_url: "https://maker.wiznet.io/forum/13984/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "MPulse"
created: "2020-08-24T15:57:13+09:00"
last_activity: "2020-08-24T15:57:13+09:00"
language: "en"
views: 500
replies: 0
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# TCP spurious retransmission

## Question

Asked by MPulse on 2020-08-24 in Ethernet Chips.

Hello,

I use a W5100S over SPI with ioLibrary_Driver.
Configuration is done via DHCP and works fine

when testing my application with putty and wireshark I experience lot’s of
TCP retransmissions in both directions . These are send despite an ACK being sent already.

After approx 40s the connection times out and is resetted.

What could cause this problem?

Best Regards

---

Source: https://maker.wiznet.io/forum/13984