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RE: [Sip] B2BUA question.
I agree that we might want to limit our discussion only within SIP
properties
of B2BUA to get some common understanding of B2BUA as a SIP logical entity.
In addition to few queries which Chinmay has pointed out,I can think of
some basic points that need to be clarified/discussed about B2BUA :
- Can B2BUA behave as a forwarding agent like Proxy, witout initiating
a new dialog ?
- Can B2BUA decide to Fork like a Proxy ?
- Can B2BUA decide to switch between UAC/UAS and Proxy functionality like
Proxy and Redirect functionality.
- Is it mandatory for B2BUA to be always call-stateful ?
- Since a UA can be stateless (RFC3261 Sec 8.2.7), is stateless B2BUA
also possible ?
- Finally, can B2BUA be called as a combination of "Proxy and UAS/UAC"
or just "UAS/UAC" combo ?
I know that the above list is not complete and possibly might have been
answered
before, but I do hope that this thread will bring some consensus on the more
concrete "SIP definition" of B2BUA.
I suggest that, to start with, there be some kind of FAQ regarding B2BUA
documented somewhere. Any Comments ?
thanks
__amit
> -----Original Message-----
> From: Padhye, Chinmay [mailto:chinmay.padhye@intel.com]
> Sent: Friday, November 08, 2002 12:26 AM
> To: Bert Culpepper; Gonzalo Camarillo; Jonathan Rosenberg; Juan Luis
> Esteban
> Cc: sip@ietf.org
> Subject: RE: [Sip] B2BUA question.
>
>
> Hello,
>
> My response is inline starting with [Chinmay].
>
> Regards,
>
> Chinmay
>
> -----Original Message-----
> From: Gonzalo Camarillo [mailto:Gonzalo.Camarillo@lmf.ericsson.se]
> Sent: Thursday, November 07, 2002 12:04 AM
> To: Padhye, Chinmay
> Cc: Bert Culpepper; sip@ietf.org
> Subject: Re: [Sip] B2BUA question.
>
>
> Hi,
>
> I do not understand what you mean by "ONLY", but I will take
> a stab at a
> response anyway. If by "ONLY" you mean that it does not
> implement other
> protocols, the answer is no. A B2BUA can receive a SIP
> request acting as
> a SIP UAC, send an LDAP query acting as an LDAP client, and
> then send a
> SIP request acting as a SIP UAC.
>
> ----------------------------------
> [Chinmay]
>
> I think its better if we separate logical entities with
> physical entities or applications that contain/behave as
> multiple logical entities. An application may contain a B2BUA
> logical entity, a LDAP client, a proxy entity, a registrar
> entity, etc. A physical entity may contain many such applications.
>
> My statement - 'the B2BUA logical entity is a
> combination of "ONLY" the UAC and UAS logical entities. Is
> this an accurate statement?', was meant only for the B2BUA
> logical entity and not for the application.
>
> Hence in the above example the B2BUA logical entity
> cannot send the LDAP query. The LDAP client, which is part of
> the same application, sends the LDAP query.
> ----------------------------------
>
> A B2BUA handles two dialogs, and it behaves as a UA for both dialogs.
> The B2BUA typically uses information in requests or responses in one
> dialog to create requests or responses in the other one. An
> example of a
> B2BUA is a 3rd party call controller.
>
> ----------------------------------
> [Chinmay]
>
> I need some more clarifications on some scenarios.
>
> Consider the following scenarios.
>
> Scenario 1 -
>
> UA1 B2BUA UA2
> |-- INVITE -------> | |
> | CID:1 | -- INVITE ---->|
> CID:x
>
> In the above scenario can 'x' take the value 1?
>
> IMO this x MUST not be equal to 1, because the UAC part
> of the B2BUA must not use CID:1 to generate the outgoing
> INVITE. Is this right.
>
> Scenario 2 -
>
> I am not sure if this part of the email belongs here or
> in the implementers list. Let me know if I should move this
> part of the email to the implementers list.
>
> UA1 B2BUA UA2 UA3
> |-- INVITE -------> | | |
> | CID:1 | -- INVITE ---->| |
> | | CID:2 | |
> | | | |
> | | -- INVITE ----------------->|
> | | CID:3 | |
> | | | |
> | | <-- 200 OK --- | |
> | <---- 200 OK ---- | | |
> | | <-- 200 OK -----------------|
> | <----- 200 OK --- | | |
> ?????????
> Can this be forwarded.
>
> In this scenario the B2BUA, on receiving the INVITE request
> from UA1, generates new INVITE request to two UAs, UA2 and
> UA3. (A similar scenario will occur if a downstream proxy
> forks and receives multiple 200 OKs.)
>
> - Can the B2BUA generate two INVITE/Requests, for one
> incoming INVITE/Request? Is this allowed by the
> protocol/definition of B2BUA?
>
> IMO this should be allowed.
>
> Now both the UAs respond with 200 OK responses.
>
> - Is the B2BUA allowed to generate two responses towards UA1
> (with different to-tags)?
>
> IMO this also should be allowed.
>
> ----------------------------------
>
> Regards,
>
> Gonzalo
>
>
> "Padhye, Chinmay" wrote:
> >
> > Hello,
> >
> > Thanks for the reply.
> >
> > So the B2BUA logical entity is a combination of
> "ONLY" the UAC and UAS logical entities. Is this an accurate
> statement?
> >
> > Regards,
> >
> > Chinmay
> >
> > -----Original Message-----
> > From: Bert Culpepper [mailto:bertculpepper@netscape.net]
> > Sent: Wednesday, November 06, 2002 6:23 PM
> > To: Padhye, Chinmay
> > Cc: sip@ietf.org
> > Subject: Re: [Sip] B2BUA question.
> >
> > Hi,
> >
> > I'll provide my opinion on why this term was included in
> RFC3261, other
> > folks may provide different/better reasons.
> >
> > The previous RFC defined UAC, UAS, Registar, Proxy, and
> Redirect Server
> > logical entities. As services (both legacy and new) were
> designed using
> > SIP, it was determined that a combination of defined
> logical entities
> > was needed to implement the services and still be compliant with the
> > specification. This particular combination became common
> enough that (I
> > presume) the authors thought it should be mentioned in the
> new RFC, to
> > avoid mis-interpretation.
> >
> > Regards,
> > Bert
> >
> > Padhye, Chinmay wrote:
> >
> > > Hello,
> > >
> > > This is from the definition of B2BUA from RFC 3261 -
> > >
> > > 'Since it is a concatenation of a UAC and UAS, no
> explicit definitions are needed for its behavior."
> > >
> > > Since the behavior of a B2BUA is the same as the
> behavior of a UAC/UAS, what was the need for defining a new
> logical entity - B2BUA? I am trying to understand the
> motivation behind adding this definition in the RFC.
> > >
> > > Regards,
> > >
> > > Chinmay
> > > _______________________________________________
> > > Sip mailing list https://www1.ietf.org/mailman/listinfo/sip
> > > This list is for NEW development of the core SIP Protocol
> > > Use sip-implementors@cs.columbia.edu for questions on current sip
> > > Use sipping@ietf.org for new developments on the
> application of sip
> > >
> > >
> >
> > _______________________________________________
> > Sip mailing list https://www1.ietf.org/mailman/listinfo/sip
> > This list is for NEW development of the core SIP Protocol
> > Use sip-implementors@cs.columbia.edu for questions on current sip
> > Use sipping@ietf.org for new developments on the application of sip
>
> --
> Gonzalo Camarillo Phone : +358 9 299 33 71
> Oy L M Ericsson Ab Mobile: +358 40 702 35 35
> Telecom R&D Fax : +358 9 299 30 52
> FIN-02420 Jorvas Email : Gonzalo.Camarillo@ericsson.com
> Finland http://www.hut.fi/~gonzalo
> _______________________________________________
> Sip mailing list https://www1.ietf.org/mailman/listinfo/sip
> This list is for NEW development of the core SIP Protocol
> Use sip-implementors@cs.columbia.edu for questions on current sip
> Use sipping@ietf.org for new developments on the application of sip
>
_______________________________________________
Sip mailing list https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use sip-implementors@cs.columbia.edu for questions on current sip
Use sipping@ietf.org for new developments on the application of sip