---
title: "W5100 and high latency links"
url: "https://maker.wiznet.io/forum/14054"
markdown_url: "https://maker.wiznet.io/forum/14054/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "JLCJoe"
created: "2020-10-27T23:35:15+09:00"
last_activity: "2020-10-27T23:35:15+09:00"
language: "en"
views: 480
replies: 0
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# W5100 and high latency links

## Question

Asked by JLCJoe on 2020-10-27 in Ethernet Chips.

Hi, we have been using the W5100 in TCP Server Mode for quite some time. It works well over the internet in low latency (<100 ms) situations. However, when we attempt to use the W5100 in higher latency (>200 ms) situations, the W5100 immediately resets the connection after the host attempt to connect.

We are using a custom [VB.net](http://VB.net) application to connect to the W5100. When we attempt to connect over a high latency (>200 ms) link, the following happens:

Host sends SYN
W5100 sends SYN/ACK
~ 300mS
Host sends ACK
W5100 sends RST

[![ACK_then_RST](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/3/3a9bb5ee162d73416eb44079b907fa30cbb70232.png) ACK_then_RST822×94 4.69 KB](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/3/3a9bb5ee162d73416eb44079b907fa30cbb70232.png)

We have set the Retry Time Register to 800ms (1F40 hex) and the Retry Count Register to 255 (FF hex) and the issue still occurs. The round trip ping time is about 290 ms. This same setup works when the round trip ping time is under 100 ms.

Here’s the Wireshark capture.
[ACK_then_RST.zip](https://maker.wiznet.io/forum/legacyFile.asp?path=pjjMU0sBccz5kYKAoDUXMdgaRHk.zip) (699 Bytes)

Can anyone point us in the right direction?

Thanks,
Joe

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Source: https://maker.wiznet.io/forum/14054