On Apr 25, 2017, at 18:46, Julian Reschke <julian.reschke@xxxxxx> wrote: > > Do you have a specific problem in mind? This work was done half a decade ago (May 18, 2012, that is), so I don’t remember all the details. RFC 6690 says: In order to convert an HTTP Link Header field to this link format, first the "Link:" HTTP header is removed, any linear whitespace (LWS) is removed, the header value is converted to UTF-8, and any percent- encodings are decoded. So we get rid of all that fun before it becomes RFC 6690 (and CoAP of course is all UTF-8 in any case). So far, we have run into one real case where that approach is a limitation, and that is in URIs: The link coap://example.com?stupid%3Dkey=4711 is not distinguishable from coap://example.com?stupid=key=4711 (The typical reaction of an implementer is “then don’t do that!” [1,2].) We know that because the CoAP protocol itself also completely runs in the UTF-8 domain (there is no percent encoding on the wire); I’m not sure that simplification actually hurt in RFC 6690 use cases yet. (Note that it is rather likely to see user-visible strings in DNS-SD instance names, which turn into “ins” link attributes, so this is not only a URI/IRI/WVUS [3] issue.) We don’t have a lot of experience with lingering legacy charsets in HTTP headers in the constrained space, so I’m sure there are other side effects. Grüße, Carsten [1]: http://www.condenaststore.com/-sp/Then-don-t-do-that-New-Yorker-Cartoon-Prints_i14788077_.htm [2]: http://www.catb.org/~esr/jargon/html/D/Don-t-do-that-then-.html [3]: https://url.spec.whatwg.org/#valid-url-string (WHATWG Valid URL String, or WVUS for short)