Removed stream feature for advertising mere protocol support, using it only for advertising support for enhanced error handling.
Support for the server dialback protocol can be indicated in two ways:
-The former method is preferred, and XMPP 1.0 servers MUST support and send the stream feature. However, the latter method is also specified herein for the purpose of backward-compatibility with older "XMPP 0.9" deployments.
-The server dialback stream feature is advertised by including in any given set of stream features a <dialback/> element qualified by the 'urn:xmpp:features:dialback' namespace; the
Note: If the Sender Domain was authenticated using SASL, the <dialback/> element SHOULD NOT be present in stream features. If a server offers both SASL and dialback, dialback SHOULD be mandatory-to-negotiate and SASL SHOULD be voluntary-to-negotiate as those terms are described in RFC 6120.
-As mentioned, support for the server dialback protocol can also be advertised by including the dialback namespace declaration in a stream header.
-Support for the server dialback protocol is indicated by inclusion of the dialback namespace declaration in the stream header.
+Although this method of advertising protocol support has been superseded by the use of stream features as originally defined in RFC 3920, the server dialback protocol predates the existence of stream features and therefore the namespace declaration method is still used in this instance.
+ +If a server supports graceful handling of dialback errors as described in Section 2.4, it MUST advertise that via a stream feature which is a <dialback/> element qualified by the 'urn:xmpp:features:dialback' namespace, including an empty <errors/> element.
+