Re: [Sipping] SIP call transfer as in draft-ietf-sipping-service-examples-02.txt

[Alan Johnston <[e-mail]>]

(trimmed to just the sipping list)

Hi Matthew,

Thanks for your comments on the draft.  You have found a typo in the 
document.  All references to Call-ID=[e-mail] should be changed 
to [e-mail].  Through cut and paste, the error is also present in 
the following messages in the document:

Section 2.5: F15, F16, F22, F23, F24, F25
Section 2.9: F7, F8, F12, F12, F14, F15, F16
Section 2.10: F20, F21, F22, F23

In answer to your second question, even when the REFER message F15 in flow 
2.5 has the correct Call-ID to make it part of the dialog between A&B, 
there is no specific reference to the held session between A&B.  This is 
not an error but the way that SIP primitives (such as REFER) work.  The 
target of the REFER does not need to understand what type of transfer is 
taking place, but only needs to know how to implement the primitive as 
requested.  The design principles behind this are described in the 
Multiparty Framework document:

    http://www.ietf.org/internet-drafts/draft-ietf-sipping-cc-framework-01.txt

Also, note that anyone implementing transfer should use the SIP Call 
Control - Transfer document as the primary reference.  Note that the next 
version of this document will actually be a sipping wg document.

    http://search.ietf.org/internet-drafts/draft-ietf-sip-cc-transfer-05.txt

Thanks,
Alan Johnston
sip:[e-mail]

At 09:43 AM 7/16/2002 +0100, [e-mail] wrote:
>Hi All,
>
>A colleague and I are currently trying to design call transfer into a system
>and are therefore consulting draft-ietf-sipping-service-examples-02.txt to
>assist us. We are finding the example of "Attended transfer" a little
>confusing; we can understand messages F1 to F14, but we do not understand
>how message F15 is able to confer to user A any useful information.
>
>1) At this stage user A has a call held (id=[e-mail]) with user B,
>but the REFER (F15) message uses a new callid ([e-mail]).
>2) Furthermore the REFER message itself does not seem to have any fields
>which relate to the held call at user A.
>
>If anyone understands how SIP call transfer is achieved, with regard to the
>"Attended transfer" example in draft-ietf-sipping-service-examples-02.txt,
>could they possibly send me an explanation?
>
>Thanks for your time,
>
>Matthew Gardiner
>Software Engineer
>Aculab
>Tel: [phone]
>Fax: [phone]
>Email: [e-mail]>
>Website: http://www.aculab.com
>
>
>
>
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