It's not necessary that the "To" and the "username" be the same. In case of IMS, the To is the Public User Identity and the username is the Private User Identity and the user can use two devices with the same public user identity and vice versa.
There is also Third Party Registers where the core S-CSCF registers on behalf of the UE with the Application Servers. This is the mechanism where the Application Servers know that the user is registered and also know the information of the Serving CSCF to proxy the call to the UE. In the third party register, the contact is the S-CSCF, the To is the identity in the Application Server and the From is the Public User that the IMS core system uses. Regards Dutt -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Paul Kyzivat Sent: Wednesday, February 21, 2007 11:26 AM To: Gary Cote Cc: [email protected]; Thirumal Margabandhu Subject: Re: [Sip-implementors] SIP registrar info - why from and to fileds are same While perhaps not widely supported, third party registration can make sense. For instance, imagine a secretary registering to the AOR of a boss. The secretary could do so by asserting the identity and credentials of the boss (which would be first party registration), but that would require the secretary to have the credentials of the boss. Or the secretary can do so using the secretary's own identity and credentials (third party registration). Paul Gary Cote wrote: > Actually, the To and From headers may be different in the case of > third-party registration. > But in the normal case, the To and From headers are somewhat redundant. > > I suppose the protocol designers could've picked just the To header > and said the From header wasn't required, but that would've made the > REGISTER method inconsistent with every other SIP method. Or, they > could've said the From header had to be present but is to be ignored > by the registrar. > > Instead, they defined the To header as the AOR to be stored in the > address binding and the From header to be the AOR of the entity > issuing the registration. It was as reasonable a choice as any other, > and had the added benefits of making the REGISTER method consistent > with other methods, and being consistent for first-party and > third-party registrations. > > Anyway ... that's always been my take on it. 'Course, I didn't > participate in the protocol design, so I could be *way* off base :) > > - g > > On 2/20/07, Thirumal Margabandhu <[EMAIL PROTECTED]> wrote: >> Hi, >> >> While SIP registrar to register that time the From and To user name >> filed will be same. What could be a reason for that. Anyone can answer for >> this.. >> >> >> >> Thanks & Regards, >> Thirumal Margabandhu >> >> ARICENT, >> Off: +91(44)- 24330550 - Extn: 341 >> Nandanam, Chennai. >> >> *********************** Aricent-Unclassified *********************** >> "DISCLAIMER: This message is proprietary to Aricent and is intended solely for the use of >> the individual to whom it is addressed. It may contain privileged or confidential information and should not be >> circulated or used for any purpose other than for what it is intended. If you have received this message in error, >> please notify the originator immediately. If you are not the intended recipient, you are notified that you are strictly >> prohibited from using, copying, altering, or disclosing the contents of this message. Aricent accepts no responsibility for >> loss or damage arising from the use of the information transmitted by this email including damage from virus." >> _______________________________________________ >> Sip-implementors mailing list >> [email protected] >> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors >> > > _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
