With draft-ietf-dnsop-svcb-https being in WGLC in DNSOP, one feedback that has come up is that the escaping and parsing for SvcParamValues is complicated. Most of this complication comes from trying to support 8-bit clean ALPN values. Ideally in presentation format the ALPN list would be something like "h2,h3,http/1.1" but at the same time the current definition of ALPN as being a series of binary octets means that we need parsing and escaping rules. When httpbis defined Alt-Svc, quite a bit of complexity showed up there as well for supporting an 8-bit-clean ALPN value while allowing for an ascii representation for most codepoints. It seems likely that other specifications may run into the same challenge.
Would there be support for updating the ALPN registry to indicate that registered ALPN values need to conform to a subset of token characters? There is a separate question for the process of making this change, but before even exploring that it seems necessary to ask the TLS WG if there are strong opinions on this one way or the other. >From a usability perspective, non-token ALPN values will have challenges in many of the systems that may try and configure them, as well as for rendering special characters in various systems that may handle ALPNs. The codepoint space is also massive so it isn't clear that there's a compelling need to support 8-bit ALPN from a code point conservation perspective. Erik
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