1. This draft consistently refers to the use of Replaces header in an
attended (3way) call scenario only. The call transfer draft (transfer-05)
has a discussion on the usage of Replaces in an Unattended Consulation Hold
with protection of transfer target in 7.5.1. The previous versions of the
transfer drafts had a section (4.6 in transfer-04) deferring the discussion
of Attended Call Transfer but the current one does not have any reference to
this. Since Replaces is envisaged as a good candidate to do protected call
transfer where the transferee does not have the capability of accepting
multiple call appearances, the Replaces draft should not restrict itself to
attended transfers and possibly even discuss and show an example of its use
for Unattended transfers.
2. Section 4 of Replaces draft-01 discusses about ignoring the Replaces
header if there is a match on more than one leg. How is it possible to have
multiple legs on a single call (identified by its call-Id) to have identical
from/to tags? Are not the tags which help distinguish one leg of a call from
another?
3. Section 5 - The call flow should show the call-Id in each message
exchange. It is not evident that the 3rd INVITE has a new Call-Id. It is
also not clear why the Replaces Header in the INVITE to the Transfer Target
is referring to Call-Id 1 when it has no knowledge of that call. It may
better help understanding the use of this header if there are full message
examples, in addition to the call-flows.
Regards,
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