High latency with Web Application Proxy

Question

Using fresh Windows Server 2019 installs for AD FS, Web Application Proxy and Exchange 2019, I have been getting high (120000ms+) latency loading ECP and any site that requests a large number of files. Downloading a single file of large size works flawlessly.

Exchange ECP takes nearly two minutes to load and then doesn't work -- the same goes for other complex sites requiring many image/CSS/JS GETs -- see example timing from Firefox:

I have spent many days trying to debug this with numerous reinstalls of AD FS and WAP servers and finding no answer in the MS forums or Googling the issue!

Answer 1

Disable HTTP/2 in IIS manager.

Such a simple solution. I hope this can save someone else the days that I have wasted.

Answer 2

Another fix, disable HTTP/2 on WAP server. Add following reg key.

Set-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp\' -Name EnableDefaultHTTP2 -Value 0

Web Application Proxy 2019 - SharePoint 2016 and Office Online Server sites won't load