Code change:
Require SETTINGSH3DATAGRAM and maxdatagramframe_size TP
Interesting thought. One way to do that replaces the entire section with this: This is certainly more concise, although it does also remove some of the explanations that help people understand the various layers involved. Or perhaps we should include those same additional details but just turn those paragraphs into bullets?
While technically true, I thought we'd said that we wanted to require all the features all of the time, but agreed, let's take that to an editorial issue if needed.
My point is that the server could support both regular HTTP and WebTransport. If a client comes in without webtransport settings and only sends GETs, that's fine. If a client comes in with webtransport settings and makes a webtransport request, that's fine. If a client comes in without webtransport settings and makes a webtransport request, that's not fine. In that case the server needs to reject the webtransport request, not kill the connection.
Ah, that makes more sense, thank you
Per discussion at IETF 114, we should explicitly require support for each layer of capabilities that are needed. There was also a discussion about whether or not we needed to require datagram support, since requiring capsules technically means that you could use a datagram capsule and implementations may exist that do not want to have datagram support at all. Documenting some of that discussion in replies to this issue, as well.
Specific to datagrams and capsules: WT supported means that capsule protocol is supported, thus you must always support capsules. Proposal: You need to have datagrams in order to do WT over HTTP/3 Adding additional signaling to negotiate datagram support introduces a lot of additional complexity and different configurations that may harm interoperability. Dropping a datagram is about as easy as doing any other error path HTTP Datagrams must already be supported in the receive direction for capsules (and you need capsules for WT) either way Intermediaries will need to be able to either translate for upstream or ensure that upstream can provide an equivalent feature set More generally: We want to explicitly call out dependencies/prerequisites so that we don't need to teach layers about other layers. For example, WT being supported doesn't mean that the layers that implement capsules, H3 datagrams, or QUIC datagrams should have any idea about the existence of WebTransport
Discussed at IETF 115, consensus in room to require all the relevant settings and transport parameters to be sent individually
So we need: HTTP Setting: SETTINGSH3DATAGRAM (0x33) with a value of 1 for HTTP datagrams QUIC TP: maxdatagramframesize with a value greater than 0 for QUIC datagrams Capsule protocol support is implicit in the upgrade token, as explicitly called out by RFC 9297 or we can require to be sent on every extended connect request as well. to be added to the existing HTTP Setting: SETTINGSENABLEWEBTRANSPORT = 1 HTTP Setting: SETTINGSWEBTRANSPORTMAXSESSIONS > 0 (although we may be removing SETTINGSENABLEWEBTRANSPORT)
SGTM I think we can skip mentioning Capsule-Protocol to match CONNECT-UDP
Would this be easier to process as a list rather than multiple separate requirements?The list text in that comment isn't correct - the server shouldn't close the connection because it's legal for the client to not support datagrams if it only sends GETs and POSTs. However, the text in this PR is correct. I propose we land the PR as-is and can make editorial changes later.

Related discussion:
text: meaning that the server is not willing to receive any WebTransport sessions. <ins> Because WebTransport over HTTP/3 requires support for HTTP/3 datagrams and the Capsule Protocol, both the client and the server MUST indicate support for HTTP/3 datagrams by sending a SETTINGS_H3_DATAGRAM value set to 1 in their SETTINGS frame (see Section 2.1.1 of HTTP-DATAGRAM). WebTransport over HTTP/3 also requires support for QUIC datagrams. To indicate support, both the client and the server MUST send a max_datagram_frame_size transport parameter with a value greater than 0 (see Section 3 of QUIC-DATAGRAM). </ins> 3.2. RFC8441 defines an extended CONNECT method in Section 4, enabled by