4 ms·

WebRTC decided they liked SCTP, so... they run it over UDP (well, over DTLS over UDP). And while HTTP/2 might fail over to HTTP/1.1, what would an SCTP session

WebRTC decided they liked SCTP, so... they run it over UDP (well, over DTLS over UDP). And while HTTP/2 might fail over to HTTP/1.1, what would an SCTP session fall back to? The problem is not that Windows doesn't have in-kernel support for SCTP (there are several user-space libraries already available, you wouldn't even need to convince MS to do anything). The blocking issue is that many, many routers on the Internet, especially but not exclusively around all corporate networks, will drop any packet that is neither TCP or UDP over IP. And if you think UDP is not optimized, I'd bet you'll find that the SCTP situation is far, far worse. And regarding 0-RTT, that only works for resumed connections, and it is still actually 1 RTT (TCP connection establish). New connections still need 2-3 round trips (1 for TCP, 1 for TLS 1.3, or 2 for TLS 1.2) with TLS; they only need 1 round trip (even when using TLS 1.2 for encryption). With QUIC, you can have true 0-RTT traffic, sending the (encrypted) HTTP request data in the very first packet you send to a host [that you communicated with previously].

kbolino 2y ago
How is userspace SCTP possible on Windows? Microsoft doesn't implement it in WinSock and, back in the XP SP2 days, Microsoft disabled/hobbled raw sockets and has never allowed them since. Absent a kernel-mode driver, or Microsoft changing their stance (either on SCTP or raw sockets), you cannot send pure SCTP from a modern Windows box using only non-privileged application code.
- simiones 2y ago
  Per these Microsoft docs [0], it seems that it should still be possible to open a raw socket on Windows 11, as long as you don't try to send TCP or UDP traffic through it (and have the right permissions, presumably). Of course, to open a raw socket you need privileged access, just like you do on Linux, because a raw socket allows you to see and respond to traffic from any other application (or even system traffic). But in principle you should be able to make a Service that handles SCTP traffic for you, and a non-privileged application could send its traffic to this service and receive data back. I did find some user-space library that is purported to support SCTP on Windows [1], but it may be quite old and not supported. Not sure if there is any real interest in something like this. [0] https://learn.microsoft.com/en-us/windows/win32/winsock/tcp-ip-raw-sockets-2 https://learn.microsoft.com/en-us/windows/win32/winsock/tcp-... [1] https://www.sctp.de/sctp-download.html https://www.sctp.de/sctp-download.html
  - kbolino 2y ago
    Interesting. I think the service approach would now be viable since it can be paired with UNIX socket support, which was added a couple of years ago (otherwise COM or RPC would be necessary, making clients more complicated and Windows-specific). But yeah, the lack of interest is the bigger problem now.

kbolino 2y ago

How is userspace SCTP possible on Windows? Microsoft doesn't implement it in WinSock and, back in the XP SP2 days, Microsoft disabled/hobbled raw sockets and has never allowed them since. Absent a kernel-mode driver, or Microsoft changing their stance (either on SCTP or raw sockets), you cannot send pure SCTP from a modern Windows box using only non-privileged application code.

simiones 2y ago
Per these Microsoft docs [0], it seems that it should still be possible to open a raw socket on Windows 11, as long as you don't try to send TCP or UDP traffic through it (and have the right permissions, presumably). Of course, to open a raw socket you need privileged access, just like you do on Linux, because a raw socket allows you to see and respond to traffic from any other application (or even system traffic). But in principle you should be able to make a Service that handles SCTP traffic for you, and a non-privileged application could send its traffic to this service and receive data back. I did find some user-space library that is purported to support SCTP on Windows [1], but it may be quite old and not supported. Not sure if there is any real interest in something like this. [0] https://learn.microsoft.com/en-us/windows/win32/winsock/tcp-ip-raw-sockets-2 https://learn.microsoft.com/en-us/windows/win32/winsock/tcp-... [1] https://www.sctp.de/sctp-download.html https://www.sctp.de/sctp-download.html
- kbolino 2y ago
  Interesting. I think the service approach would now be viable since it can be paired with UNIX socket support, which was added a couple of years ago (otherwise COM or RPC would be necessary, making clients more complicated and Windows-specific). But yeah, the lack of interest is the bigger problem now.