draft-holmberg-mmusic-oa-pt.xml

<?xml version="1.0" encoding="iso-8859-1"?>
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<!DOCTYPE rfc SYSTEM "rfc2629.dtd"[]>
<?rfc toc="yes" ?>
<?rfc compact="yes" ?>
<?rfc sortrefs="no" ?>
<rfc ipr="trust200902" category="std" docName="draft-ietf-mmusic-dtls-sdp-00.txt" updates="3264" submissionType="IETF" xml:lang="en">
  <front>
    <title>
		SDP Offer/Answer: Payload type number usage clarification
	</title>
    <author fullname="Christer Holmberg" initials="C.H." surname="Holmberg">
        <organization abbrev="Ericsson">Ericsson</organization>
        <address>
            <postal>
                <street>Hirsalantie 11</street>
                <city>Jorvas</city>
                <region></region>
                <code>02420</code>
                <country>Finland</country>
            </postal>
            <phone></phone>
            <email>christer.holmberg@ericsson.com</email>
        </address>
    </author>     	

    <date year="2016" />
    <area>RAI</area>
    <abstract>
		<t>
            This document updates RFC 3264 by clarifying the scope of a mapping from a particular 
            dynamic payload type number to a codec (or codec configuration) is for a given 
            RTP media flow direction within a session.
        </t>
    </abstract>
</front>
<middle>
    <section title="Introduction">        
        <t>
            This document updates RFC 3264 <xref format="default" pageno="false" target="RFC3264"/> 
            by clarifying the scope of a mapping from a particular dynamic payload type number 
            to a codec (or codec configuration) is for a given RTP media flow direction within a session.
        </t>
    </section>
		
    <section title="Conventions">
		<t>
			The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
			"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
			document are to be interpreted as described in <xref target="RFC2119"></xref>.
		</t>
    </section>

    <section title="Update to RFC 3264">
            <t>
                This section updates the first paragraph of section 8.3.2 of RFC 3264.
            </t>
            <figure>
                <artwork align="left" alt="" height="" name="" type="" width="" xml:space="preserve"><![CDATA[

Update to section 8.3.2
-----------------------                

OLD TEXT:

   The list of media formats used in the session MAY be changed.  To do
   this, the offerer creates a new media description, with the list of
   media formats in the "m=" line different from the corresponding media
   stream in the previous SDP.  This list MAY include new formats, and
   MAY remove formats present from the previous SDP.  However, in the
   case of RTP, the mapping from a particular dynamic payload type
   number to a particular codec within that media stream MUST NOT change
   for the duration of a session.  For example, if A generates an offer
   with G.711 assigned to dynamic payload type number 46, payload type
   number 46 MUST refer to G.711 from that point forward in any offers
   or answers for that media stream within the session.  However, it is
   acceptable for multiple payload type numbers to be mapped to the same
   codec, so that an updated offer could also use payload type number 72
   for G.711.

   
NEW TEXT:

   The list of media formats used in the session MAY be changed.  To do
   this, the offerer creates a new media description, with the list of
   media formats in the "m=" line different from the corresponding media
   stream in the previous SDP.  This list MAY include new formats, and
   MAY remove formats present from the previous SDP. The scope of a mapping 
   from a particular dynamic payload type number to a codec (or codec 
   configuration) is for a given RTP media flow direction within a session. 
   The same dynamic payload type number can be mapped to another codec in 
   another RTP media flow direction within the same session. The mapping 
   MUST NOT change to a different coded (or coded configuration) for the 
   duration of a session. Eventhough not recommended, for a given direction, 
   multiple dynamic payload type numbers can be mapped to the same codec 
   (or codec configuration). Note that a mapping has been created once an 
   endpoint has sent and offer or answer, describing the mapping for a 
   given direction. Even if the offer or answer is rejected or discarded, 
   or if RTP media associated with the mapping is never sent, the mapping 
   MUST NOT change for the given direction within the session.

   Within an offer or answer, the mapping is for the RTP media flow direction 
   towards the offerer/answerer, unless the media flow is indicated as 'sendonly' 
   in which case the mapping is for the media flow direction from the 
   offerer/answerer.
      
                ]]></artwork>
            </figure>
	</section>
    
	<section title="Security Considerations">
		<t>
            The security considerations associated with the SDP offer/answer mechanism
            are described in RFC 3264. As this document only clarifies the existing procedures,
            it does not impact the security considerations.
		</t>
	</section>
	                   
	<section title="Acknowledgements">
		<t>
            TBD
        </t>
	</section>
		
	<section title="Change Log">	
		<t>[RFC EDITOR NOTE: Please remove this section when publishing]</t>
        <t>Changes from draft-holmberg-mmusic-od-pt-xx
			<list style="symbols">
                <t>Add text</t>
			</list>
		</t>		
	</section>
    
</middle>

<back>
    <references title="Normative References">
		<?rfc include="reference.RFC.2119"?>
		<?rfc include="reference.RFC.3264"?>
        <?rfc include="reference.RFC.4566"?>
    </references>    
</back>
</rfc>