Re: [AVT] comments on section 10 ofdraft-ietf-avt-rapid-acquisition-for-rtp-01

["Ali C. Begen (abegen)" <abegen at cisco.com>]

> -----Original Message-----
> From: Roni Even [mailto:Even.roni at huawei.com]
> Sent: Wednesday, June 17, 2009 3:00 AM
> To: Ali C. Begen (abegen); avt at ietf.org
> Subject: RE: [AVT] comments on section 10 ofdraft-ietf-avt-rapid-acquisition-for-rtp-01
> 
> Ali,
> Thanks, I understand the RAMS-R and RAMS-T port usage and the logic behind
> it.
> As for the RAMS-I section 6.2 says
> 
> " Note that RS learns the IP address information for RR from the
>        RAMS-R message it received.  (This description glosses over the
>        NAT details.  Refer to Section 10 for a discussion of NAT-related
>        issues.)"
> 
> So according to the above if using RTP/RTCP multiplexing, the RTP unicast
> stream is sent to the address from which the RAMS-R has arrived.

Yes. Whether there is a NAT or not (or whether muxing is used or not), the RAMS-R will always indicate RR's public IP address and RS sends its packets to that IP address. But, this part does not say anything regarding the ports. The ports to be used depend on whether there is a NAT or not and the signaling in the RAMS-R/pubports/etc.

-acbegen

> Roni
> 
> -----Original Message-----
> From: Ali C. Begen (abegen) [mailto:abegen at cisco.com]
> Sent: Wednesday, June 17, 2009 12:13 AM
> To: Roni Even; avt at ietf.org
> Subject: RE: [AVT] comments on section 10
> ofdraft-ietf-avt-rapid-acquisition-for-rtp-01
> 
> Inline.
> 
> > -----Original Message-----
> > From: Roni Even [mailto:Even.roni at huawei.com]
> > Sent: Tuesday, June 16, 2009 1:46 PM
> > To: Ali C. Begen (abegen); avt at ietf.org
> > Subject: RE: [AVT] comments on section 10
> ofdraft-ietf-avt-rapid-acquisition-for-rtp-01
> >
> > Ali,
> > From figure 2 and the text that follows
> >
> > " A Retransmission Source may equally act as a Burst Source.  The
> >    Retransmission Source may also incorporate the Feedback Target
> >    ([I-D.ietf-avt-rtcpssm] permits the feedback target to be a
> >    retransmission server, since it is a logical function to which RRs
> >    send their unicast feedback), and we will use the term Retransmission
> >    Server (RS) in the remainder of the document to refer to a single
> >    physical entity comprising these three entities that share state.
> >    Note that the same method (with the identical message flows) would
> >    also apply in a scenario where rapid acquisition is performed by a
> >    feedback target co-located with the media source."
> >
> > I assumed that we are only dealing with the case that the RS is a single
> > entity and not three different entities with different addresses
> 
> You are correct. There is a single retransmission server that does all the
> work. Other types of scenarios may be considered in the future.
> 
> > I also thought that this was agreed in previous discussions
> 
> Yup.
> 
> 
> > If my understanding is not correct I will review the draft since the
> current
> > text is not explicit enough to specify which part is doing each message. I
> > saw that RAMS-R is going to feedback target but RAMS-T is going to RS
> which
> > is not specifying a specific address according to you.
> 
> Right, RAMS-T goes to RS as well but it goes to the RTCP port of the unicast
> session not the FT of the primary session (since it is to terminate the
> unicast burst). What I am trying to say below is different, though, which is
> that we cannot make an assumption on the port RR wants to use in the unicast
> session (e.g., to receive the burst) based on the port it used for the
> primary session.
> 
> -acbegen
> 
> 
> > Roni
> >
> > -----Original Message-----
> > From: Ali C. Begen (abegen) [mailto:abegen at cisco.com]
> > Sent: Tuesday, June 16, 2009 10:00 PM
> > To: Roni Even; avt at ietf.org
> > Subject: RE: [AVT] comments on section 10
> > ofdraft-ietf-avt-rapid-acquisition-for-rtp-01
> >
> > Remember that the RAMS-R (RR->RS) message is NOT on the retransmission
> > (unicast) session, it's on the primary session since it is sent to the
> > feedback target of the primary SSM session. Thus, the source port RR uses
> to
> > send RAMS-R "cannot" be assumed to be the destination port it wishes to
> > receive the unicast burst on.
> >
> > If you agree with this statement, it is clear why we need port signaling.
> > Muxing will not help much here. It will just reduce the number of signaled
> > ports from 2 to 1.
> >
> > -acbegen
> >
> >
> > > -----Original Message-----
> > > From: avt-bounces at ietf.org [mailto:avt-bounces at ietf.org] On Behalf Of
> Roni
> > Even
> > > Sent: Tuesday, June 16, 2009 10:08 AM
> > > To: avt at ietf.org
> > > Subject: [AVT] comments on section 10
> > ofdraft-ietf-avt-rapid-acquisition-for-rtp-01
> > >
> > > Hi,
> > >
> > > I looked at section 10 and have some comments
> > >
> > >
> > >
> > > 1.       If RTP/RTCP multiplexing is used, there is no need for any
> > specific operation
> > > from the RR side. The RR sends the RAMS-R message to the RS from the
> port
> > it wants to
> > > receive the RAMS-I and RTP payload. The RS just sends the information to
> > the port from
> > > which it received the RAMS-R and not to the one in the SDP
> > >
> > > 2.       In the case where there is no RTP/RTCP multiplexing, the RAMS-R
> > RTCP message will
> > > go to the RS and the RAMS-I will go to the port on the RR from where the
> > RAMS-R was
> > > received. For the RTP, the RR does not know if it has a NAT on the way
> to
> > the RS and
> > > should try to get a routable address (using STUN for example) and
> > providing the port to
> > > the RS ( we still need to agree on how to do it)
> > >
> > > 3.       If the above two points are correct than the RR receive port in
> > the SDP is not
> > > really useful
> > >
> > >
> > >
> > > Roni Even