Alt-Svc text -- starts to address #87

draft-ietf-quic-http.md

@@ -97,27 +97,71 @@ defined in {{!RFC2119}}.
 
 # QUIC advertisement
 
-A server advertises that it can speak HTTP-over-QUIC via the Alt-Svc HTTP
-response header.  It does so by including the header in any response sent over a
-non-QUIC (e.g. HTTP/2) connection:
+A server advertises that it can speak HTTP/QUIC via the Alt-Svc
+({{!RFC7838}}) HTTP response header, using the ALPN token "hq".
 
-   Alt-Svc: quic=":443"
+Thus, a server could indicate in an HTTP/1.1 or HTTP/2 response that HTTP/QUIC
+was available on UDP port 443 by including the following header in any
+response:
 
-In addition, the list of QUIC versions supported by the server can be specified
-by the v= parameter.  For example, if a server supported both version 33 and 34
-it would specify the following header:
+   Alt-Svc: hq=":443"
 
-   Alt-Svc: quic=":443"; v="34,33"
+## Draft version identification
+
+> **RFC Editor's Note:**  Please remove this section prior to publication of a
+> final version of this document.
 
-On receipt of this header, a client may attempt to establish a QUIC connection
+Only implementations of the final, published RFC can identify themselves as 
+"hq". Until such an RFC exists, implementations MUST NOT identify themselves 
+using these strings. 
+
+Implementations of draft versions of the protocol MUST add the string "-" and 
+the corresponding draft number to the identifier. For example, 
+draft-ietf-quic-http-01 is identified using the string "hq-01". 
+
+Non-compatible experiments that are based on these draft versions MUST append 
+the string "-" and an experiment name to the identifier. For example, an 
+experimental implementation based on draft-ietf-quic-http-09 which reserves an 
+extra stream for unsolicited transmission of 1980s pop music might identify
+itself as "hq-09-rickroll". Note that any label MUST conform to the "token"
+syntax defined in Section 3.2.6 of [RFC7230]. Experimenters are encouraged to
+coordinate their experiments on the ietf-quic-wg@w3.org mailing list.
+
+## QUIC version hints {#alt-svc-version-hint}
+
+This document defines the "v" parameter for Alt-Svc, which is used to provide
+version-negotiation hints to HTTP/QUIC clients.
+
+In addition, a list of QUIC versions supported by the server can be specified by
+the v= parameter.  Syntax:
+
+    v = quoted-versions
+    quoted-versions = DQUOTE *( version-string "," ) version-string DQUOTE
+    version-string = token; percent-encoded QUIC version
+
+For example, if a server supported both version Q033 and Q034 it would specify
+the following header:
+
+    Alt-Svc: hq=":443"; v="Q034,Q033"
+
+Where multiple versions are listed, the order of the values reflects the
+server's preference (with the first value being the most preferred version).
+
+QUIC versions are four-octet sequences with no additional constraints on format. 
+Octets not allowed in tokens ({{!RFC7230}}, Section 3.2.6) MUST be 
+percent-encoded as per Section 2.1 of {{!RFC3986}}. Consequently, the octet 
+representing the percent character ("%", hex 25) MUST be percent-encoded as 
+well. 
+
+On receipt of this header, a client MAY attempt to establish a QUIC connection
 on port 443 and, if successful, send HTTP requests using the mapping described
-in this document.
+in this document.  Servers SHOULD list only versions which they support, but MAY
+omit supported versions for any reason.
 
 Connectivity problems (e.g. firewall blocking UDP) may result in QUIC connection
 establishment failure, in which case the client should gracefully fall back to
 HTTP/2.
 
-
 # Connection establishment
 
 HTTP-over-QUIC connections are established as described in {{QUIC-TRANSPORT}}.
@@ -747,6 +791,35 @@ HTTP/2.
 
 # IANA Considerations
 
+## Registration of HTTP/QUIC Identification String
+
+This document creates a new registration for the identification of HTTP/QUIC in
+the "Application Layer Protocol Negotiation (ALPN) Protocol IDs" registry
+established in {{?RFC7301}}.
+
+The "hq" string identifies HTTP/QUIC:
+
+  Protocol:
+  : HTTP over QUIC
+
+  Identification Sequence:
+  : 0x68 0x71 ("hq")
+
+  Specification:
+  : This document
+
+## Registration of Version Hint Alt-Svc Parameter
+
+This document creates a new registration for version-negotiation hints in the
+"Hypertext Transfer Protocol (HTTP) Alt-Svc Parameter" registry established in
+{{!RFC7838}}.
+
+  Parameter:
+  : "v"
+
+  Specification:
+  : This document, {{alt-svc-version-hint}}
+
 ## Existing Frame Types
 
 This document adds two new columns to the "HTTP/2 Frame Type" registry defined in