Hi, Section 19.3 of RFC 3261 states the following:
" The tag parameter is used in the To and From header fields of SIP messages. It serves as a general mechanism to identify a dialog, which is the combination of the Call-ID along with two tags, one from each participant in the dialog. When a UA sends a request outside of a dialog, it contains a From tag only, providing "half" of the dialog ID. The dialog is completed from the response(s), each of which contributes the second half in the To header field. The forking of SIP requests means that multiple dialogs can be established from a single request. This also explains the need for the two-sided dialog identifier; without a contribution from the recipients, the originator could not disambiguate the multiple dialogs established from a single request." As the RFC clearly states that the dialog is completed from the responses thus it should be the UAS to generate the To Tag in the response not the UAC. In the case of Forking of single SIP request, to avoid the ambiguity in multiple dialogs contribution from the recipients (UAS), in our case To Tag, is necessary. Regards, Amit Kumar Singh amit2.si...@aricent.com -----Original Message----- From: sip-implementors-boun...@lists.cs.columbia.edu [mailto:sip-implementors-boun...@lists.cs.columbia.edu] On Behalf Of Arun Tagare Sent: Tuesday, August 05, 2014 11:45 AM To: sip-implementors@lists.cs.columbia.edu Subject: [Sip-implementors] : No To-Tag in INVITE why? Hi All, Can any one explain me Why there is no To-Tag in the INVITE Request? And what happens if i add To-Tag in the INVITE Request? -- With Regards Arun A. Tagare +91 9449 029729 _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors "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 Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
