Re: [AVTCORE] Comments on draft-ietf-avtcore-feedback-supression-rtp-06.txt

[Roni Even <[e-mail]>]

Hi Tom,
I reviewed this section in the 6.2 and mostly agree with your suggestion.
I also suggested to Qin to look also at the difference when there is
retransmission or not and also if the retransmission is in unicast or
multicast. 

Regards
Roni 

> -----Original Message-----
> From: Van Caenegem, Tom (Tom) [mailto:tom.van_caenegem@alcatel-
> lucent.com]
> Sent: Tuesday, September 13, 2011 5:11 PM
> To: Magnus Westerlund; Qin Wu
> Cc: [e-mail]; draft-ietf-avtcore-feedback-supression-
> [e-mail]
> Subject: RE: [AVTCORE] Comments on draft-ietf-avtcore-feedback-
> supression-rtp-06.txt
> 
> Magnus,
> 
> If you want a view of the RAMS' authors, please check:
> http://tools.ietf.org/html/draft-vancaenegem-avtcore-retransmission-
> for-ssm-00
> 
> I did ask Qin to refer to this draft which provides a detailed
> description on how feedback suppression can work for RAMS topology.
> 
> In summary:
> 
> The BRS sends a NACK or TPLR message to the DS, where the SSRC in this
> NACK or TPLR message is the one of the BRS. The DS forwards/reflects
> this message down on the primary SSM. This procedure will allow
> isolated feedback suppression, when RTP receivers only trigger FB
> suppression when recognising the SSRC as belonging to the BRS to which
> they report.
> 
> Tom
> 
> > 4. Section 6.2: "If the BRS impacted by packet loss has been told the
> > actual packet loss, the BRS MAY choose to create new Third Party Loss
> > Report message and send it to the receivers in the downstream link.
> > "
> >
> > I don't understand how the BRS can inject any message into the SSM
> > tree, as the source anchor of the SSM tree is up at the multicast
> > source. Thus a BRS needs to tell the distribution source to send
> > something down stream on its behalf.
> >
> >
> >
> >
> > [Qin]: It is possbile for BRS to tell the distrbution source to send
> > TPLR down on its BRS. My question is Is the BRS similar to
> > Distribution source as an intermediary between multicast source and
> >
> > downstream receivers? Why BRS can not inject in between while
> > Distribution Source can?
> 
> My understanding what that the BRS is in fact not owner of their own
> SSM session, only help nodes that are receiver of the SSM session but
> not DS in it. And having the BRS send something to the DS which is only
> valid for its little part of a large SSM session is strange.
> 
> But RAMS authors view would be appreciated.