Code change:
QUIC, and applications ought not to use private keys intended for server authentication as keys for client authentication. <del> Moreover, Transport Services systems MUST NOT automatically fall back </del> <ins> Moreover, Transport Services systems must not automatically fall back </ins> from secure protocols to insecure protocols, or to weaker versions of <del> secure protocols.  For example, if an application requests a specific version of TLS, but the desired version of TLS is not available, its connection will fail.  Applications are thus responsible for implementing security protocol fallback or version fallback by creating multiple Transport Services Connections, if so desired. Alternatively, a Transport Services system MAY allow applications to specify that fallback to a specific other version of a protocol is allowed. </del> <ins> secure protocols (see equivalence).  For example, if an application requests a specific version of TLS, but the desired version of TLS is not available, its connection will fail.  Applications are thus responsible for implementing security protocol fallback or version fallback by creating multiple Transport Services Connections, if so desired.  Alternatively, a Transport Services system MAY allow applications to specify that fallback to a specific other version of a protocol is allowed. </ins>

Related discussion:
text: I think it would also be useful to somehow better explain that in figure 3 the API function is ONE part of the system.
See linked PR first please to see if this resolves this?
A PR was merged that addressed important text issues with separation of requirements and overview, and should more clearly set out that the requirements are for the system. The question of whether the overall TAPS systems requirements belong in this ID; the API; or a separate RFC needs some discussion based on the review, before this can be closed.
Many good text improvements in the PR NAME but I noticed two smaller updates in the PR that I think were incorrect. Fixed in
The review comment showed were many places where the wording of architecture can be improved. There are some high level principles that I think should remain in the architecture document. The decision in today's interim is to review the architecture to get this more into a shape that is valuable as a reference, and then check the updated draft.
I now suggest the issues are addressed and we close this issue without moving text between documents
I agree with that; closing.
Overall review: I think we need to keep the normative language for the key features that differentiate the API. I'd really like to use REQUIRED, RECOMMENDED, rather MUST and SHOULD - because these are not protocol operation requirements, but are implementation requirements to conform. This includes requirements based on Minset - where the WG dervied this API: This is after all why the WG worked on Minset as the basis of the API. I suggest we group all the requirements on architecture as short one or two sentence blocks (preferably as a bullet or definition list) collected into a single subsection, so they are easy to find and read and we say that these are the key architectural requirements. We insert this new requirements text either their own section, or in section 1.3 (although I am open to other places where we can call-out the architectural requirements). The following are key requirements, that define the TAPS architecture: It is RECOMMENDED that functionality that is common across multiple transport protocols is made accessible through a unified set of TAPS interface calls. As a baseline, a Transport Services system interface is REQUIRED to allow access to the minimal set of features offered by transport protocols {{?I-D.ietf-taps-minset}}.