On Wed, 2006-01-25 at 07:43 +0000, Matthew Gardiner wrote:
> Furthermore, would I be right in saying that INVITE and SUBSCRIBE are the
> only requests which are able to create dialogs?

Let me add my two cents:

Some SIP systems create implicit subscriptions, usually when UAs
register, they are given subscriptions to the MWI, etc.  In a case like
this, the NOTIFYs still should be inside dialogs, one for each
subscription, and so the first NOTIFY of a subscription will establish
the call-id/to-tag/from-tag.

There is an internet-draft going around that codifies setting up
implicit subscriptions, IIRC.

Also, REGISTERs are done in sequences which look a lot like dialogs, in
that they maintain a call-id/to-tag/from-tag and CSeq count, but they do
not keep a route set.  Or at least, they maintain a call-id; it seems
from RFC 3261 that each REGISTER and response have to-tag and from-tag,
but it's not clear whether they're expected to be the same between
REGISTERs with the same call-id.

Dale

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