RE: [SIP] 3PCC and REFER method
<ferreiro_j@tsm.es> Wed, 03 January 2001 10:45 UTC
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From: ferreiro_j@tsm.es
Subject: RE: [SIP] 3PCC and REFER method
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Date: Wed, 03 Jan 2001 11:31:34 +0100
Thank you for your reply, Eric. Comments below >I'd worry about a third-party directing an end-point to establish a call. >In particular, there are interesting billing issues (although one could say >this solves a billing issue). For example, if the HTTP server sends the "Go >call the controller" message to Terminal A, the network sees a call >origination from Terminal A. That may, or may not, be the intention of the >service provider. IMHO I do not find the billing issue as a cons for using REFER to replace the scenario of generating two outbound calls from the controller. I cannot imagine a SIP based network billing policy less flexible than the one currently offered in the traditional telecom environment -i.e. with IN and 800 numbers. Anyway, in case of dealing with such a restrictive billing policy, the controller can send the REFER to Terminal B instead, and it makes sense with the Click-to-dial example, since the web portal will a) own also the service representative/customer care site b) have a bussiness relationship with the company that runs the service representative/customer care site. The main reason for my suggestion is to avoid the complexities related to make the controller try to stablish two outbound calls. In the cellular operator I work for, I just can think on one such a service currently deployed, that is USSD-to-dial. The cellular prepaid customers when roaming, and since the charging policy MUST be applied in real time, are not allowed to perform explicit outbound calls (due to barrings included in their user profile) since these calls will not be charged in the Home Prepaid Apliccation Server; so the prepaid user is forced to send a USSD/SMS message to the Home Prepaid Application Server including the B number in the body text. The Home Prepaid.. acts as a controller and makes two outbound calls to terminal B and terminal A. Due to billing constraints -both A leg and B leg are charged to the caller, A leg is always international, and B leg is 70% likely to belong to the home country-, the controller makes the outbound call to B first, and if B is not reachable (busy, disconnected, network congestion, etc.) notifies A number -tipically SMS based-. If, and only if the second leg is properly stablished, the call to A is performed. This is currently the only way to perform calls for prepaid roamers in many countries, so they have to deal with really curious scenarios: a) the A user gets annoied when receiving a failure notification after 20-60 seconds waiting; people are more used to listen busy tones, and tend to think the service offered is failing, it is clearly a "mediterranean" psicological attitude :) b)if the B number is an IVR menu (tipically when you try to reach your own voice mailbox) since the B leg is the first leg to be stablished, the first piece of information provided by the IVR menu is lost (imagine losing "Press 1 to listen your messages, press 2 to change your settings") c) User A may receive an inbound call while waiting for the controller to stablish the A leg, i.e. busy; and reject the attempt performed by the controller. Who should pay for the B leg already stablished? (b. t. w. a "nice" hacking with the proposed scenario for click-to-dial is to answer a different SDP to the RE-INVITE at the A leg as warned in draft-rosenberg-sip-3pcc-01.txt page 12; Amazon customer representative could be K.O. quite fast after several attacks) It sounds to me more natural, from the A user point of view, to receive a REFER -this means the SIP browser will interact with A in order to ask for permission to make the outbound call- and follow the progress of the call to B through the controller. -b.t.w. there is a new approach to solve this prepaid roaming problem based on Wireless IN (CAMEL) standards but this is not the point discussed here- Anyway, there must be any other reasons not to use REFER in the 3PCC scenario rather than billing ... or is it billing and I am wrong? regards Javier >What precisely is the issue with having the controller issuing the INVITEs >to A and B? >> -----Original Message----- >> From: sip-admin@lists.bell-labs.com >> [mailto:sip-admin@lists.bell-labs.com]On Behalf Of >> Javier_Ferreiro_Garcia/UT03329/PLATAFORMAS_DE_SERVICIOS/TSM@tsm.es >> Sent: Friday, December 29, 2000 6:00 AM >> To: sip@lists.bell-labs.com >> Subject: [SIP] 3PCC and REFER method >> >> >> Hi >> I would like to open again the issue discussed in >> http://lists.bell-labs.com/pipermail/sip/2000q4/004739.html >> >> >>What happens when there is not an active SIP (INVITE) session >> between the >> >>referer and referee ? Sending an INVITE in this case may have unwanted >> >>effects (like initiating a call). Are you proposing that either a) you >> would >> >>only send the INVITE/BYE if a corresponding SIP (INVITE) sessions exists >> or >> >>b) that REFERS are not allowed outside of a SIP session? >> >> > What does a REFER outside of a session mean? >> >> and apply this idea to the scenario proposed in >> draft-rosenberg-sip-3pcc-01.txt Figure 1 and specifically the >> example included for Click-to-dial application. >> >> In this alternative scenario for Click-to-dial, the controller, after >> receiving the request via HTTP, do not INVITE both A and B, but >> rather send >> a REFER to A, asking A to INVITE the CONTROLER ITSELF. When the controller >> receives the INVITE SDP A from A, checks in its internal database who is >> supposed to be contacted by A (in this case B) and sends INVITE >> SDP A to B. >> In this case I think the re-INVITE loop could be avoided by applying this >> scenario which is more similar to a normal INVITE between two parties. >> >> In this alternative scenario the referer (i.e. the controller) and the >> referee (i.e. the web-surfer) are OUTSIDE of a SIP session, but INSIDE an >> HTTP session. It could also be decided the referee to be the IP phone from >> the customer service representative, if the web-surfer IP phone >> either does >> not support REFER or is a PSTN endpoint. >> >> The reason to include as content of Refer-To header not B but the >> controller itself is to let the controller do its job in a more >> general way >> (i.e. imagine click-to-dial + mid-call-announcement) >> >> If the scenario is not the one described for Click-to-dial, but for Mid >> Call AnnouncementCapability, the controller does not either set >> up the call >> to A or send the REFER method to A, but rather receive the INVITE from A >> and act as a "termination and reinitiation point" for control purposes >> (i.e. disconnect and reconnect A to a media server under certain >> conditions) as defined in draft-rosenberg-sip-3pcc-01.txt >[snip] _______________________________________________ SIP mailing list SIP@lists.bell-labs.com http://lists.bell-labs.com/mailman/listinfo/sip _______________________________________________ SIP mailing list SIP@lists.bell-labs.com http://lists.bell-labs.com/mailman/listinfo/sip
- RE: [SIP] 3PCC and REFER method ferreiro_j
- [SIP] 3PCC and REFER method Javier_Ferreiro_Garcia/UT03329/PLATAFORMAS_DE_SERVICIOS/TSM
- RE: [SIP] 3PCC and REFER method Eric Burger