Re: [AVTCORE] Gen-ART review of draft-ietf-avtcore-idms-09

["Brandenburg, R. (Ray) van" <[e-mail]>]

-----Original Message-----
From: Romascanu, Dan (Dan) [mailto:[e-mail]] 
Sent: maandag 10 juni 2013 16:57
To: Brandenburg, R. (Ray) van
Cc: [e-mail]; General Area Review Team; Roni Even ([e-mail]); [e-mail]
Subject: RE: Gen-ART review of draft-ietf-avtcore-idms-09





> -----Original Message-----
> From: Brandenburg, R. (Ray) van [mailto:[e-mail]]
> Sent: Monday, June 10, 2013 5:52 PM
> To: Romascanu, Dan (Dan)
> Cc: [e-mail]; General Area Review Team; Roni Even 
> ([e-mail]); [e-mail]
> Subject: RE: Gen-ART review of draft-ietf-avtcore-idms-09
> 
> Hi Dan,
> 
> See below...
> 
> Best regards,
> 
> Ray
> 
> -----Original Message-----
> From: Romascanu, Dan (Dan) [mailto:[e-mail]]
> Sent: maandag 10 juni 2013 16:35
> To: Brandenburg, R. (Ray) van
> Cc: [e-mail]; General Area Review Team; Roni Even 
> ([e-mail]); [e-mail]
> Subject: RE: Gen-ART review of draft-ietf-avtcore-idms-09
> 
> 
> Yes, we seem to get closer and closer, focus on one last issue (and 
> much agreement deleted)
> 
> Thanks and Regards,
> 
> Dan
> 
> 
> 
> > -----Original Message-----
> > From: Brandenburg, R. (Ray) van [mailto:[e-mail]]
> > Sent: Monday, June 10, 2013 5:27 PM
> > To: Romascanu, Dan (Dan)
> > Cc: [e-mail]; General Area Review Team; Roni Even 
> > ([e-mail]); [e-mail]
> > Subject: RE: Gen-ART review of draft-ietf-avtcore-idms-09
> >
> > Hi Dan,
> >
> > Please see inline. We seem to be converging:)
> >
> > Ray
> 
> > > > 7. In Section 8:
> > > >
> > > >    The timestamp is formatted based on the NTP
> > > >    timestamp format as specified in [RFC5905].  If this field is
> > > empty,
> > > >    then it SHALL be set to 0.  This field MAY be left empty if 
> > > > none
> > or
> > > >    only one of the receivers reported on presentation timestamps.
> > > >
> > > > Why a MAY here? Especially for the case when none of the 
> > > > receivers reported, what content can be set there but 0 ?
> > > >
> > > > [Ray: I believe it should be up to the implementation to decide 
> > > > how it wants to handle the case of there being only one receiver 
> > > > who reported on presentation timestamps].
> > > >
> > > [[DR]] OK, so the cases when none of the receivers reported and 
> > > one receiver only reported should be dealt with differently. This 
> > > needs to be clarified.
> > >
> > > [Ray] What exactly is the problem with the MAY here? IMO it 
> > > doesn't create any interop issues: whatever is the reason for 
> > > setting the value to 0, to the client the end result is the same: ignore it.
> > >
> >
> > [[DR]] In the case when none of the receivers reported we want to 
> > avoid leaving some garbage in this field which could be interpreted 
> > differently - don't we?
> >
> > [Ray] I think I see where we disagree. The paragraph says: "If this 
> > field is empty, then it SHALL be set to 0. This field MAY be left 
> > empty if none or only one of the receivers reported on presentation 
> > timestamps". The way I read this is as: In the case the field is 
> > declared empty (= contains NULL information), it SHALL be set to 0.
> > There can be different reasons for declaring the field empty/NULL, 
> > one of those reasons is if none or only one receiver reported on 
> > presentation timestamps. To me, the paragraph doesn't say that this 
> > is the only possible reason, but it does specify very clearly that 
> > if you decide the field should be empty, you SHALL set it to zero.
> >
> >
> 
> [[DR]] But then, why do not you take out 'if none or' - because for 
> the option of 'none' there is no alternative but the 'null' 
> information, and the MAY does not make sense.
> 
> [Ray] The fact that no receiver reported on the packet presentation 
> timestamp does not necessarily mean that the MSAS does not want to 
> indicate a proposed packet presentation timestamp. The absence of such 
> reports just means that the proposed playout moment might not be 
> realistic, or be supported by any receiver.
> 

[[DR]] yes, but is the field set to anything but 0 in such cases? 

[Ray] If the MSAS decides to leave the field empty, it is set to 0 according to the SHALL. If the MSAS decides to include a timestamp anyway, it is set to whatever value the MSAS proposes. 

Dan
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