This is widely confusing. Once upon a time the dialog concept wasn't
very well defined. REGISTER and INVITE use some of the same elements, so
it looks a bit like REGISTER establishes a dialog. Since then the
fundamentals of dialogs have been clarified, and new uses of dialogs
(e.g. SUBSCRIBE) have been defined. While REGISTER uses some of the
elements of a dialog, it doesn't use them all, and just doesn't qualify
as a dialog establishing request.
You should just view REGISTER as following its own set of rules, without
regard for the rules defined for dialog establishment.
Paul
[EMAIL PROTECTED] wrote:
> Hi
>
> I have a doubt about the dialog concept in RFC 3261.
>
> In Section 4 Overview of Operation, it says that the combination of the To
> tag, From tag, and Call-ID completely defines a peer-to-peer SIP
> relationship between two user agent (Alice and Bob) and is referred to as
> a dialog.
>
> In section 12, it says that a dialog is identified at each UA with a
> dialog ID, which consists of a Call-ID value, a local tag and a remote
> tag.
>
> In section 10.2 Constructing the REGISTER Request, it says that a REGISTER
> request does not establish a dialog.
>
> A REGISTER request contains From tag and a Call-ID. The 200 response to
> the REGISTER typically contains To tag. As a result, a registration
> transaction when completed has Call-ID, From tag and To tag to define a
> peer-to-peer SIP relationship between a SIP endpoint and the Registrar.
> Why this peer-to-peer relationship is not considered as a dialog?
>
> Thanks
>
> Guang
>
>
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