Re: [AVT] WGLC comments on draft-ietf-avt-ports-for-ucast-mcast-rtp-11: Part 1 SSRC spaces

["Ali C. Begen (abegen)" <[e-mail]>]

> -----Original Message-----
> From: Magnus Westerlund [mailto:[e-mail]]
> Sent: Monday, January 17, 2011 10:15 AM
> To: Ali C. Begen (abegen)
> Cc: IETF AVT WG; [e-mail]
> Subject: Re: [AVT] WGLC comments on draft-ietf-avt-ports-for-ucast-mcast-rtp-11: Part 1 SSRC spaces
> 
> Ali C. Begen (abegen) skrev 2011-01-17 14:23:
> >> Lets try again to describe the above paragraph, as we clearly
> >> missunderstanding each other.
> >>
> >> The client has an SSRC that is uses for regular RTCP feedback to the
> >> Retransmission server. If is want to send a NACK, then it include a
> >> Token Verification Request. In that message it include the SSRC of the
> >> client. This SSRC comes from the Multicast RTP sessions SSRC space.
> >
> > Right.
> >
> >> Then the Retransmission server may send an RTCP message back to the
> >> client in a form of the Token Verification Failure message. This message
> >> include the SSRC of the requesting client. As this Token Verification
> >> Failure message is sent in the RS -> Client leg of the created unicast
> >
> > Yes, and the server simply gets this SSRC from the request message.
> >
> >> session, but is in reality a response to the message in the multicast
> >
> > Yes, maybe it was a NACK sent for the multicast session.
> >
> >> RTP session. This creates a case where it is uncertain which SSRC space
> >> the SSRCs in the failure message belong to. Based on network selectors,
> >> e.g. UDP ports this message is in the unicast space. But semantically it
> >> belongs to the Multicast channel.
> >>
> >> Please make it clear in the description in 4.4 what space the SSRC
> >> values belongs to.
> >
> > In the failure message:
> >
> > SSRC of Packet Sender: This is server's SSRC, which equals the SSRC of the respective primary multicast stream.
> > SSRC of Requesting Client: This SSRC is directly copied from the Token Verification Request message (this text already
> exists in 4.4).
> >
> > Is the "packet sender SSRC" definition fine with you?
> 
> I think I would like to have extra warning: "Note, theis SSRC value are
> from a different SSRC space than the one used in the Unicast RTP session."

OK.

-acbegen
 
> >> Yes, for mapping message that is fine. The thing I can complain about is
> >> why the SSRC fields aren't there own bullets and instead hidden in the
> >> pre-facing text to the figures?
> >
> > We can move them to the bullets. We probably did not so because, they are pretty much part of the baseline format.
> 
> I think it has its point when we do have some irregularities here in
> some cases.
> 
> Cheers
> 
> Magnus Westerlund
> 
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