Constant MIXED_PREFERENCE_11 

const MIXED_PREFERENCE_11: &str = "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 \
                                   Objects via both Subgroup streams and Datagrams in response to \
                                   a SUBSCRIBE, it SHOULD close the session with an error of \
                                   'Protocol Violation'";