New draft: HTTP Version Translation of the Capsule Protocol

Hi HTTPBIS

Last year, Kazuho asked us to consider whether an intermediary can translate unrecognized HTTP Upgrade Tokens across HTTP versions [1].  The discussion concluded that this is not possible: an unrecognized Upgrade Token might have an arbitrary interaction with an HTTP extension, and the choice of method in HTTP/1.1 is not defined.

A few days ago, Kazuho and I considered the narrower question of whether this translation is possible within the context of the Capsule Protocol.  We have written a draft that would enable such translations:

https://www.ietf.org/archive/id/draft-kb-capsule-conversion-00.html

This draft would enable forward-compatible implementation of Capsule Protocol gateways by committing to some invariants about the Capsule Protocol.

--Ben Schwartz

[1] https://lists.w3.org/Archives/Public/ietf-http-wg/2023OctDec/0005.html