NetTcp retransmissions

[remcovhu]

Using a NetCore server as per https://github.com/CoreWCF/samples/tree/main/Scenarios/Getting-Started-with-CoreWCF/NetCoreServer and a Framework client as per https://github.com/CoreWCF/samples/tree/main/Scenarios/Getting-Started-with-CoreWCF/NetFrameworkClient both on the same windows 10 20H2 workstation. The server is configured as windows service:

var builder = Host.CreateDefaultBuilder(args) .ConfigureWebHostDefaults(w => w.UseStartup<Startup>());

        builder.ConfigureWebHost(w => w.UseKestrel());
        builder.ConfigureWebHost(w => w.UseNetTcp(rti.Port));
        
        builder.UseWindowsService();
        
        builder.Build().Run();

When first calling the server it takes about 5 seconds to get an answer. Subsequent request are answered in a few milliseconds. After some time without making a request this behavior repeats.

Wiresharking the first request gives the following:

Obviously this is not a workable situation but I'm kinda lost here. What am I doing wrong?

[remcovhu]

This issue manifests itself also in the unmodified samplecode. Using Core server and Framework client. Http works like a charm, NetTcp is slow and causes numerous TCP retransmissions.