Unicode HTTP Host: Header Field?

Question

What does the Host: header look like for a Unicode domain. e.g. æon.com in the MOST STANDARD format (assuming RFC 5987? or is it something else?)?

I am developing a transparent proxy that will need to work across different browsers and languages.

Could you paste an example of a Host: æon.com HTTP header, same as a Wireshark Packet Dump would produce, un-decoded and specifically the Host: field.

Answer 1

International domain names are encoded in Punycode. "æon.com" is represented by "xn--on-0ia.com".

Answer 2

a) RFC 5987 is only applicable to certain header field parameters, not entire header fields.

b) The host header field should be whatever the host name in the HTTP URI (!!!, not IRI), was (as explained by deceze, puny-coded).