Invalid Track Alias/Subscribe ID are a protocol violation (#616)

Fixes: #458

Author: ianswett

draft-ietf-moq-transport.md

@@ -2247,6 +2247,12 @@ the datagram.
 An endpoint that receives an unknown stream or datagram type MUST close the
 session.
 
+The publisher only sends Objects after receiving a SUBSCRIBE or FETCH.  The
+publisher MUST NOT send Objects that are not requested.  If an endpoint receives
+an Object it never requested, it SHOULD terminate the session with a protocol
+violation. Objects can arrive after a subscription or fetch has been cancelled,
+so the session MUST NOT be teriminated in that case.
+
 Every Track has a single 'Object Forwarding Preference' and the Original
 Publisher MUST NOT mix different forwarding preferences within a single track.
 If a subscriber receives different forwarding preferences for a track, it