Re: [MMUSIC] draft-ejzak-mmusic-msrp-usage-data-channel

["Makaraju, Maridi Raju (Raju)" <[e-mail]>]

>> Suppose the intent is to close one MSRP session and immediately open a
> >> new one. Is it permissible to simply update the SDP to describe the new
> >> MSRP session, reusing the channel number, without first doing an O/A to
> >> confirm the closure of the old one?
> > <Raju>
> > The intent is not to reuse a datachannel (same or a different subprotocol)
> > before close. We will clarify that such a reuse is not supported.
> > The problem with such reuse is, previous datachannel MUST be reset before
> > it is used for new subprotocol, else the data from previous data channel
> use
> > will interfere with the new data channel use.
> 
> My question is: Can I just close it in-band (with a reset) and then send
> an offer for the new usage of the channel?

<Raju>
No. To reuse a closed data channel, a new SDP offer/answer, to convey the 
data channel closure (which excludes the corresponding a=dcmap and may include
other new data channels via new a=dcmaps), must be done. This can be done either 
in a new offer initiated from this end or in an SDP answer this end generates.
The reason for this is to avoid various race conditions between SDP offer/answer
and SCTP reset arrival times.
Also, this is not a limiting thing as a new data channel can easily be created 
using a new stream id, range is for which is large, without restarting underlying
SCTP/DTLS association.

If you agree I will update draft-ejzak-mmusic-data-channel-sdpneg and
draft-ejzak-mmusic-msrp-usage-data-channel with these clarifications.
</Raju>

BR
Raju