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3.1.5.9 Connection-Oriented Media Address Support

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In the SDP message, as specified in [RFC4566], the m= line is used to specify the transport for the given media type. The supported transport can be either User Datagram Protocol (UDP) or TCP. TCP is a connection-oriented transport by which the media is exchanged. UDP is not connection-oriented. The following is an SDP message fragment showing an m= line specifying that TCP be used as the media transport, as defined in [RFC4571].

m=audio 50004 TCP/RTP/AVP 8 97 101

However, the connection-oriented transport SHOULD NOT be used when ICE, as defined in [IETFDRAFT-ICENAT-06] or [IETFDRAFT-ICENAT-19], is not enabled on the offering application and the answering application. This applies to any offer or answer received from an application that does not support ICE.

If the offer or answer is received from an application that supports ICE, according to the ICE specifications in [IETFDRAFT-ICENAT-06] and [IETFDRAFT-ICENAT-19], the port and the transport specified in the m= line are referred to as the active address or the address that will be tried first in the ICE methodology to establish connection.

Application sharing SHOULD<11> use [MS-ICE2] over TCP.

The ICE scenario is applicable if both peers support ICE, which can be established by examining the SDP offer and SDP answer.

For audio or video media, or other media types, a connection-oriented or TCP transport for the active addresses in the first SDP offer or SDP answer MUST NOT be used. A subsequent SDP offer/SDP answer exchanged in a re-INVITE might have a connection-oriented transport for the active address, depending on the operation of ICE.

For audio or video media, or other media types, any connection-oriented transport specified in the m= line in the first SDP offer or SDP answer SHOULD<12> be rejected, as specified in [RFC3264] section 6.