Behaviour difference in Expect100Continue in TLS1.2 & TLS1.3

Question

Hi
We observed the following difference in sending the payload in TLS1.2 & TLS1.3.
When Expect100Continue to set to true,
TLS1.2
Send the pay load along with the header without waiting for 100 continue response.
TLS1.3
Send the empty pay load along with the header and waiting for 100 continue response.

Could you please confirm whether the behavior in TLS1.2 is a bug or not.

Answer 1

Hello there,

There are reports of some different behavior of TLS 1.3 in Windows 11 and I guess this is also one of them . You can try to share this via the feedback hub along with logs so that this can be analyzed.

These are some example threads that shares similar experience. TLS 1.3 doesn't work on Windows 11 through SChannel API https://learn.microsoft.com/en-us/answers/questions/708734/tls-13-doesn39t-work-on-windows-11-through-schanne.html

A WCF request with "Expect: 100-continue" header returns a 400 bad request. It is happening only TLS 1.3 https://learn.microsoft.com/en-us/answers/questions/1002620/a-wcf-request-with-34expect-100-continue34-header.html

I hope this information helps. If you have any questions please let me know and I will be glad to help you out.

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