Re: [Sipping] Request for Open discussion about SIP mobility

[Paul Kyzivat <[e-mail]>]

Interesting document. I am happy to see more exploration of the subject 
area.

The a=bicast approach only seems sufficient when there is a single media 
stream to deal with. If there are multiple media streams, then it gets 
tricky to match them all up. The grouping framework is a better 
solution. It would be helpful to see an example where there there are 
two media streams that each need to be bicast.

One thing that isn't clear to me is now the recipient of the bicast 
traffic matches up the two streams and decides what media to render. Is 
there enough information in RTP, even when transcoding has been 
performed on one or both of the streams, to allow this to work reliably? 
(Disclaimer - I know little about RTP.)

And related to that - what about non-RTP media? This same scenario is 
applicable to less conventional media, such as IM. While technically it 
is possible to follow the pattern you have outlined to establish bicast 
MSRP, the identification of duplicate messages will require a different 
solution.

I also would be interested to hear your thoughts about the urgency of 
cutover and the mechanics of doing it. I know you state an assumption 
that there is some overlap in coverage of the two access networks. And 
without that things get very difficult. But the overlap may not be very 
extensive, so it may be wise to quickly get from one to the other 
entirely - for signaling as well as media. So for instance it might be 
desirable to switch the signaling path to AN2 ASAP, before bicasting 
ceases. Or, it may be prudent to find a way to maintain "bicast" 
signaling paths as well for the time when it is uncertain which AN might 
remain available.

	Thanks,
	Paul



Haruki Izumikawa wrote:
> Hello folks,
> 
> I'd like to have an open discussion about SIP-based mobility in this ML.
> Mobility managements using SIP have been actively studied and developed
> worldwide since "Mobility Support Using SIP" (by Elin and Henning) was
> published. SIP-based mobility would have strong advantages such as its
> great affinity for an application as well as flexibility, i.e., terminal
> mobility can be optimally supported independent from underlying network.
> On the other hand, despite many advantages, it is not used for
> large-scale commercial yet. In addition, the discussion about SIP-based
> mobility in IETF seems to be undynamic.
> These days, a multimode terminal is getting popular. Each access
> networks, e.g., cellular and WLAN, have different characteristics in
> terms of throughput or delay. In such a heterogeneous network, SIP
> becomes more useful tool for mobility management because of its
> flexibility. The quality of a multimedia service can be adaptively
> changed in accordance with a nature of an access networks even after
> changing an access network. I think it is time to resume discussing
> about SIP-based mobility. For your information, I have submitted I-D
> regarding seamless session handoff by SIP-based bicasting.
> http://www.ietf.org/internet-drafts/draft-izumikawa-sipping-sipbicast-01.txt
> I would be happy to hear frank opinions of SIP specialists.
> 
> Best regards,
> 
> Haruki
> 
> 
_______________________________________________
Sipping mailing list  https://www.ietf.org/mailman/listinfo/sipping
This list is for NEW development of the application of SIP
Use [e-mail] for questions on current sip
Use [e-mail] for new developments of core SIP