V11 P3 Update: HTTP/3 early request processing added to kestral http3.md

[wadepickett]

Description

PR #36991 introduces the following new feature for ASP.NET Core in .NET 11 Preview 3:

The Preview 3 feature introduces an observable behavior change in Kestrel HTTP/3 connection handling — requests are now processed without waiting for the QUIC control stream and SETTINGS frame. This is important for developers troubleshooting HTTP/3 latency, understanding connection behavior, and tuning performance. The current HTTP/3 article doesn't mention control stream or SETTINGS frame behavior at all.

Suggested changes

1. Add a new section after "HTTP/3 benefits" (after line 48, before "HTTP/3 requirements")

## Early request processing

:::moniker range=">= aspnetcore-11.0"

Starting with .NET 11, Kestrel starts processing HTTP/3 requests without waiting for the control stream and SETTINGS frame first. This optimization reduces first-request latency on new HTTP/3 connections.

In previous versions, Kestrel waited to receive the QUIC control stream and its initial SETTINGS frame before processing any request streams. This is no longer required, which means the first request on a new connection completes faster.

:::moniker-end

Page URL

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/servers/kestrel/http3?view=aspnetcore-10.0

Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/fundamentals/servers/kestrel/http3.md

Document ID

d8ff0551-6287-7921-b18d-2cad70fce012

Platform Id

7276b517-7b69-3190-7a11-dd1e9db1f99e

Article author

@wtgodbe

Metadata

• ID: 57282931-0741-9ae0-1bc3-1918160769e2
• PlatformId: 7276b517-7b69-3190-7a11-dd1e9db1f99e
• Service: aspnet-core
• Sub-service: fundamentals

Related Issues

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Associated WorkItem - 569850