Codec Freedom -- Specifications -- Redirecting the Voice Connection with SIP

Just like it is possible to change the codec of the communication at hand, so it is possible to modify the signaling properties.  To this end, the treatment of MIME-type message/sip should be interpreted as aimed at the local phone, provided that its Content-Disposition is set to session.  The addresses used in field like From: and To: may be tel: URIs and may or may not need renaming before forwaring to local infrastructure.  The remote party may also drop the headers describing the partners, in which case each local end would substitute an address that is understood by the local endpoint to indicate transition over the modified G.711 connection.

Remote SIP inquiries should never be taken lightly, and be scrutinised for security impact.  It is probably safe to consider an incoming SIP message over AMQP as compatible with the SIP message that would pass over the Internet, and through our local proxies.  Any SDP attachments can be treated in the same manner as when they would have been passed over AMQP.