slowstart

Hi Peter, are you seeing longer wait times for N-400 and citizenship processing? Can one travel out of the country for a few weeks while the application is pending or will this impact the residency requirements?

You may be interested in this: https://techcommunity.microsoft.com/t5/networking-blog/makin.... The gist is that yes QUIC has higher CPU usage but all OS platforms are investing in UDP hardware offloads and optimizations to level the playing field. While the only IETF standard that will come out is HTTP/3, our implementation MsQuic powers both HTTP/3 and SMB proving the general purpose nature of the transport. We are not there yet in terms of an application that's only powered by QUIC because UDP reachability is not 100%, so you need a fallback. Most apps will either use HTTP/3 and fallback to HTTP/2 or use QUIC directly and have to fall back to secure L7 over TCP.

Our QUIC implementation MsQuic can run in both kernel and user mode on Windows. A PAL allows the core protocol logic to be agnostic.

Thanks for the heads up. We will investigate to see what fraction of connections end up losing these options. Pacing TCP is certainly on our roadmap. Our QUIC implementation MsQuic paces by default already.

Windows historically defaulted to accepting timestamps when negotiated by the peer but didn't initiate the negotiation. There are benefits to timestamps and one downside (12 bytes overhead per packet). Re. syncookies, that's an interesting problem but under a severe syn attack, degraded performance is not going to be the biggest worry for the server. We might turn them on but for the other benefits, no committed plans. Re. pacing profile, no that's pacing implemented at the TCP layer itself (unlike fq disc) and is an experimental knob off by default.

That's not expected. Are you using loopback sockets or are these sockets on different endpoints? Is this unidirectional or bidirectional traffic, i.e. are you doing both transfers from A to B and B to A simultaneously?

I cannot comment on queuing disciplines and limits in future products. Re. TCP_NOTSENT_LOWAT, you may want to look at the Ideal Send Backlog API that allows an application to have just more than BDP queued to keep the performance at the maximum throughput while minimizing the amount of data queued: https://docs.microsoft.com/en-us/windows/win32/winsock/sio-i...

It's called R(ecent) Acknowledgement and yes the work came out of Google. This is the single biggest change to TCP loss recovery in a decade. It is now a Standards Track RFC: https://datatracker.ietf.org/doc/html/rfc8985. The Windows implementation was one of the earliest amongst a handful and Microsoft participated in the standardization.

You should look into the RSS configuration. https://docs.microsoft.com/en-us/windows-hardware/drivers/ne... and https://docs.microsoft.com/en-us/windows-server/networking/t...

You are spot on. PktMon is the next generation tool in newer Windows 10 versions and brings many of the same benefits referred to in this blog - particularly being able to view packet captures and traces together in the same text file. And WPA is also very useful when analyzing performance problems.

PktMon is the next generation tool in newer Windows 10 versions and brings many of the same benefits referred to in this blog - particularly being able to view packet captures and traces together in the same text file.

I lead the Windows TCP team. We blogged about recent TCP advancements which is very relevant: https://techcommunity.microsoft.com/t5/networking-blog/algor...

We are currently testing HTTP/3 support in IIS/http.sys internally. Cannot comment on any external product release timelines.

Connection migration is part of the current Internet-Drafts. The generalized support for multi-path (i.e. usage of more than one path at the same time) is postponed to a future version of the protocol. You can follow the standards work here: https://quicwg.org/

We do extensive testing including stress testing and make use of tooling that can catch bugs early. We also partner with internal security teams to do fuzz testing and security reviews for all networking code. That said, none of the networking stacks deployed widely today are completely immune to security vulnerabilities. Responsible disclosure also plays an important role.

There is currently no standardization for QUIC APIs. You can check out the MsQuic API here: https://github.com/microsoft/msquic/blob/master/docs/API.md

Since this had to run in kernel mode on Windows to power our HTTP stack, C was the language of choice. There exist other open source implementations of QUIC in C++ and Rust etc.

RPC/gRPC are certainly possible use cases for the QUIC transport protocol. But no, we have not yet explored the use of QUIC in this context. For now we are focused on workloads that will benefit the most from the tail latency performance and security improvements that QUIC brings.

Please fire away any questions you may have! I lead the team that built this library.

This blog has details on current development status and adoption within Microsoft: https://techcommunity.microsoft.com/t5/networking-blog/msqui...