Original text:
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>  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> 

Reviewer comments:
This proposal consolidates normative language into the section on design principles (now requirements), using the suggestions in .
Please review the latest updates!
Early art-art review of draft-ietf-taps-architecture My first observation and request is that the group rethink the separation of the architecture and interface documents. It is a warning-sign that the interface document is a normative reference for the architecture document. As the documents are currently constructed, a new reader cannot grasp the architecture without inferring some of it through reading the interface. Consider reformulating the architecture document as an overview - introduce principles, concepts, and terminology, but don't attempt to be normative. (There are signs that this may already be, or have been, a path the document was being pushed towards). If nothing else, rename it, and acknowledge that the actual architecture is specified using the interface definition. Note that the first sentence of the Overview in the interface document also highlights the current structural problem.
I don't entirely agree with this ART-ART comment: I think I might well agree with moving more of the description to this Arch document, but as discussed before, I also think it useful here to set the actual requirements for the architecture, and to define the architecture. It may need to be much clearer that this architecture consists of more the API.
For completeness, this is the first statement of the interface document review: This document reads fairly well. I have some structural concerns (see the early review of the architecture document). In particular I think this document contains the actual definition of the architecture and some of that is inferential.
Discussion at September 2021 interim: pass through this document with a view toward making it a high level introduction, not an architecture definition: "An Introduction to the Transport Services Architecture". remove normative language from this document (moving it to API, where necessary). move details not useful in a high level intro to API.
I disagree with this conclusion at first pass—we did a specific analysis and pass on this over a year ago, with PR . The normative language and the standards-track aspect was very intentional and something the WG had consensus on. The point is that the API is a specific incarnation of the TAPS architecture, but there are overarching architectural properties that go beyond a specific abstract API.
I completely agree with Tommy here, and recommend we fix this in . We should also of course check for any stray text or missing concepts. 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}}. A Transport Services system automates the selection of protocols and features and network, based on a set of Properties supplied through the TAPS interface. It is RECOMMENDED that a Transport Services system offers Properties that are common to multiple transport protocols. Specifying common Properties enables a system to appropriately select between protocols that offer equivalent features. This design permits evolution of the transport protocols and functions without affecting the programs using the system. Specifying common Properties enables a Transport Services system to appropriately select an appropriate network interface. It is RECOMMENDED that a system offers Properties that are common to a variety network layer interfaces and paths. This design permits racing of different network paths without affecting the programs using the system. Applications using the Transport Services system interface are REQUIRED to be robust to the automated selection provided by the system, including the possibility to express requirements and preferences that constrain the choices that can be made by the system. If two different Protocol Stacks can be safely swapped, or raced in parallel (see Section 4.2.2), by the Transport Services system then they are considered to be "equivalent". Equivalent Protocol Stacks need to meet the requirements for racing specified in section XX. Applications using a Transport Services system MAY explicitly require or prevent the use of specific transport features (and transport protocols) and XXXinterfaces using the "REQUIRED" and "PROHIBIT" preferences. This allows an application to constrain the set of protocols and features that will be selected for the transport service. It is RECOMMENDED that the default usage by applications does not necessarily restrict this selection, so that the system can make informed choices (e.g., based on the availability of interfaces or set of transport protocols available for the specified remote endpoint). When a Transport Services system races between two different Protocol Stacks, both SHOULD use the same security protocols and options. However, a Transport Services system MAY race different security protocols, e.g., if the application explicitly specifies that it considers them equivalent. Transport Services systems MUST NOT automatically fall back from secure protocols to insecure protocols, or to weaker versions of secure protocols. A Transport Services system MAY allow applications to specify that fallback to a specific other version of a protocol is allowed. It is RECOMMENDED that in normal use, a Transport Services system is designed so that all selection decisions result in consistent choices for the same network conditions when they have the same set of preferences. This is intended to provide predictable outcomes to the application using the transport service. I would then suggest to use lower case within other parts of the document - except were pointed to from here, (we could refer to the requirements subsection, if we thought necessary).
for discussion at the interim, but IMO we could start the interim with a PR based on these suggestions and work from there.
I suspect that we need more protocol-specific properties to be able to talk to various kinds of native protocol peers (other than TCP and UDP: these should already work fine with what we have, I believe). A concrete example: we're hiding stream numbers. In NEAT, we needed to make them configurable though, because we wanted a NEAT client to be able to talk to a native SCTP server, where an application may expect certain type of data to arrive via a certain stream number. I suspect that we may need something similar for a QUIC peer. Should we address this? (I'd say yes) How .. is it a protocol-specific (per-Message) property? (I'd say yes... and perhaps a per-Connection property too, with text explaining that the per-Message one automatically becomes the Connection default unless otherwise specified) What other such things are we missing... what other expectations may e.g. a native QUIC or SCTP application have that we just cannot fulfil with our current system?

Revised text:
QUIC, and applications ought not to use private keys intended for server authentication as keys for client authentication.  <ins> Moreover, Transport Services systems must not automatically fall back </ins> from secure protocols to insecure protocols, or to weaker versions of  <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>