neeraj gupta wrote:
I have looked at the
draft-ietf-sipping-cc-transfer-05.txt
All the call flows show a HOLD before the REFER.
Is it necessary ? Can there be call transfer -
therefore
REFER sent before HOLD ?
( QSIG allows call transfer with out hold)
IMO, as far as all the sip specs go, there is no need for the hold.
However, if you don't do the hold, some UA will have to deal with both
old and new media streams that are both active, and make some workable
decision about what to render.
I guess this isn't a big deal with audio - there will be some sort of
glitch at the transition, but its probably no big deal. It may be more
of a problem with other media.
For video I gather there may be a training period which could cause more
difficulty. Somebody posted a draft not too long ago about this.
When people start using MSRP for IM it will present a different set of
problems. Unlike voice, or even video, where a few packets can be lost
without much impact, with IM people will not tolerate the loss of even a
single packet. So the handoff during a transfer needs to be perfect.
Paul
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