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

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

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. 

Dan
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