Re: [rohc] 答复: Re: Feedback formats

[Klaus Warnke <[e-mail]>]

Cai,
 > non mode transitions: should we send feedback with mode parameter?
No, I don't think so. Why?
If there is no mode transition in progress, there is no need to
send a mode parameter.  But if there is a need to send a feedback
option (clock resolution, for example) you  must use feedback-2
and then the mode parameter must set correct.

 > if YES, which case we could use feedback-1 in profile RTP?
Where do you see a problem to use feedback-1 together with the
RTP profile?
If the decompressor ACKs an context update, a feedback-1 packet
is ok.  This could be done with a feedback-2 packet too, but why
sending larger packets than needed?  The only exception I know is
using RTP profile in optimistic mode with sparse ACK (5.7.6.) and
sending no ACK.  If you sending no ACK, no feedback-1 is
needed, because NACK is always a feedback-2 packet. But for
reliable mode you need feedback-1.

br
Klaus Warnke

[e-mail] wrote:
>
> Klaus, Calle,
>
> Thank you for the detailed interpretation and sorry for joining the 
> discussion so late.
>
> I think there is no doubt that when mode transitions, any feedback 
> should be sent with mode transition parameter;
>
> i.e., use feedback-2
>
> the question is that the feedback logic of non mode transitions: 
> should we send feedback with mode parameter?
>
> if YES, which case we could use feedback-1 in profile RTP?
>
> Thanks
> 	
> *caiwei 167981*
> LTE Development Department | LTE开发部
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>
> *Klaus Warnke <[e-mail]>*
>
> 2009-07-16 22:15
>
> 	
> 收件人
> 	Carl Knutsson <[e-mail]>, [e-mail]
> 抄送
> 	[e-mail]
> 主题
> 	Re: [rohc] Feedback formats
>
>
>
> 	
>
>
>
>
>
> Calle, Cai,
>
> yes, I'm wrong.
> "short cut" means, there is no handshake procedure needed, but using
> feedback-1 was too short.
>
> br
> Klaus
>
> Carl Knutsson wrote:
> > Klaus, Cai,
> >
> > Using the "short cut" as Klaus describes below is not really allowed in
> > RFC3095. Section 5.6.1 is quite clear that all feedback during a mode
> > transition must carry a CRC option. The mode parameter must also be set
> > to O to transfer from U-mode to O-mode. FEEDBACK-1 doesn't have a mode
> > field and cannot carry feedback options.
> >
> > Klaus, I guess you refer to the last paragraph of section 5.6.2. It
> > should not be interpreted by its own. I agree that the wording is a bit
> > unfortunate, but I can still not see how it can be interpret it this
> > way. FEEDBACK-1 cannot be used for mode transfer between U-mode and
> > O-mode. The compressor simply don't have the information to which mode
> > to transfer to.
> >
> >
> > Cheers,
> >
> > /Calle
> >
> >
> > Klaus Warnke wrote:
> >  
> >> Hello cai,
> >>
> >> I'm not completely sure what your mean.
> >>
> >> First, there is a "short cut" to switch from U to O
> >> mode (5.6.2.). In this case, a feedback-1 is sufficient, because
> >> the receiving of any feedback shows to compressor that a feedback
> >> channel is available and this is the precondition for bidirectional
> >> optimistic mode.
> >>
> >> Ideally the mode transition should be profile independent. But for the
> >> IR/IR-DYN packet it isn't due to a design flaw. Only the dynamic chain
> >> of the RTP Header contains the 'M' (5.7.7.6.) flag to transmit a
> >> compression mode. For the other profiles you must use a extension-3.
> >>
> >> Hope that helps.
> >>
> >> If not, could you please explain the problem more detailed?
> >>
> >> br
> >> Klaus Warnke
> >>
> >>
> >> [e-mail] wrote:
> >>    
> >>> RFC 3095 describes that when mode transitions, any feedback should be
> >>> sent with mode transition parameter;
> >>>
> >>> at the same time, the feedback logic of decompressor in U/O/R mode
> >>> also send feedback with mode parameter.
> >>>
> >>> there is a doubt that which case we could use feedback-1 in 
> profile RTP?
> >>>
> >>> Thanks
> >>>                  
> >>> *caiwei 167981*
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