Re: [MMUSIC] draft-ietf-ice-rfc5245bis-00: Impacts due to ICE solution for indicating exclusive support of RTP/RTCP-mux.

[Paul Kyzivat <[e-mail]>]

Christer,

The new text seems to imply there is a valid situation where RTP is used 
but RTCP is not *used*. Is that intended? Does RTP allow that?

(I realize it is done in the wild, but this would legitimize it.)

	Thanks,
	Paul

On 12/7/15 8:52 AM, Christer Holmberg wrote:
> Hi,
>
> In order to clarify that the absence of an RTCP component does NOT by
> default mean that RTCP is not used, I suggest some additional text to
> the new text.
>
> Regards,
>
> Christer
>
> Section 4.1.1.1:
>
> --------------------
>
> OLD TEXT:
>
>     Each component has an ID assigned to it, called the component ID.
>
>     For RTP-based media streams, the RTP itself has a component ID of 1,
>
>     and RTCP a component ID of 2.  If an agent is using RTCP, it MUST
>
>     obtain a candidate for it.  If an agent is using both RTP and RTCP,
>
>     it would end up with 2*K host candidates if an agent has K IP
>
>     addresses.
>
> NEW TEXT (based on e-mail discussion):
>
> Each component has an ID assigned to it, called the component ID.
>
> For RTP-based media streams, unless RTP and RTCP are multiplexed on
>
> the same port (RTP/RTCP multiplexing), the RTP has a component ID of 1
>
> and RTCP a component ID of 2. In case of RTP/RTCP multiplexing, a
>
> component ID of 1 is used for both RTP and RTCP.
>
> When candidates are obtained, unless the agent knows for sure that
>
> RTP/RTCP multiplexing will be used (i.e. the agent knows that the
>
> other agent also supports, and is willing to use, RTP/RTCP multiplexing),
>
> or unless the agent only supports RTP/RTCP multiplexing,
>
> the agent MUST obtain a separate candidate for RTCP. If an agent has
>
> obtained a candidate for RTCP, and end up using RTP/RTCP multiplexing,
>
> the agent does not need to perform connectivity checks on the RTCP
> candidate.
>
> If an agent is using separate candidates for RTP and RTCP, it will end up
>
> with 2*K host candidates if the agent has K IP addresses.
>
> NOTE: The responding agent, when obtaining its candidates, will
> typically know
>
> whether the other agent supports RTP/RTCP multiplexing, in which case it
> will
>
> not need to obtain a separate candidate for RTCP.
>
> <new>NOTE: There needs to be a signalling mechanism to indicate whether
>
> the absence of a component ID of 2 means that RTCP is not used, or that
>
> RTP/RTCP multiplexing is used. Such mechanism is outside the scope of
>
> this document.</new>
>
> Section 4.2:
>
> ---------------
>
> OLD TEXT:
>
> Each component has an ID assigned to it, called the component ID.
>
>        For RTP-based media streams, the RTP itself has a component ID of 1,
>
>        and RTCP a component ID of 2.  If an agent is using RTCP, it MUST
>
>        obtain candidates for it.
>
> NEW TEXT:
>
> Each component has an ID assigned to it, called the component ID.
>
>        For RTP-based media streams, the RTP itself has a component ID of 1,
>
>        and RTCP a component ID of 2.  If an agent is using RTCP, it MUST
>
>        obtain candidates for it<new>, unless the agent only supports
> multiplexing
>
>        of RTP and RTCP on the same port</new>.
>
> <new>NOTE: There needs to be a signalling mechanism to indicate whether
>
> the absence of a component ID of 2 means that RTCP is not used, or that
>
> RTP/RTCP multiplexing is used. Such mechanism is outside the scope of
>
> this document.</new>
>
>
>
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