Broaden language to include alternate-host Alt-Svc uses

draft-ietf-quic-http.md

@@ -99,31 +99,29 @@ defined in {{!RFC2119}}.
 
 # QUIC Advertisement
 
-A server advertises that it can speak HTTP/QUIC via the Alt-Svc ({{!RFC7838}})
-HTTP response header (or the semantically equivalent Alt-Svc HTTP/2 Extension
-Frame Type), using the ALPN token defined in {{connection-establishment}}.
+An HTTP origin advertises the availability of an equivalent HTTP/QUIC endpoint
+via the Alt-Svc HTTP response header or the HTTP/2 ALTSVC frame ({{!RFC7838}}),
+using the ALPN token defined in {{connection-establishment}}.
 
-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:
+For example, an origin could indicate in an HTTP/1.1 or HTTP/2 response that
+HTTP/QUIC was available on UDP port 443 at the same hostname by including the
+following header in any response:
 
     Alt-Svc: hq=":443"
 
 On receipt of an Alt-Svc header indicating HTTP/QUIC support, a client MAY
-attempt to establish a QUIC connection on the indicated port and, if successful,
-send HTTP requests using the mapping described in this document. Servers SHOULD
-list only versions which they support, but MAY omit supported versions for any
-reason.
+attempt to establish a QUIC connection to the indicated host and port and, if
+successful, send HTTP requests using the mapping described in this document.
 
 Connectivity problems (e.g. firewall blocking UDP) can result in QUIC connection
-establishment failure, in which case the client should gracefully fall back to
-HTTP/2.
+establishment failure, in which case the client SHOULD continue using the
+existing connection or try another alternative endpoint offered by the origin.
 
 
 ## QUIC Version Hints {#alt-svc-version-hint}
 
-This document defines the "quic" parameter for Alt-Svc, which is used to provide
-optional version-negotiation hints to HTTP/QUIC clients. QUIC versions are
+This document defines the "quic" parameter for Alt-Svc, which MAY be used to
+provide version-negotiation hints to HTTP/QUIC clients. QUIC versions are
 four-octet sequences with no additional constraints on format. Syntax:
 
     quic = version-number
@@ -138,6 +136,8 @@ header:
 
 Where multiple versions are listed, the order of the values reflects the
 server's preference (with the first value being the most preferred version).
+Origins SHOULD list only versions which they support, but MAY omit supported
+versions for any reason.
 
 # Connection Establishment {#connection-establishment}