Thank you Donat. You have confirmed my suspicions. The reference to the section in the RFC is very useful.
John Quick Smartvox Limited Tel: +44-1727-221221 > From: Donat Zenichev <donat.zenic...@gmail.com> > Sent: 03 February 2021 09:57 > To: john.qu...@smartvox.co.uk; OpenSIPS users mailling list > <users@lists.opensips.org> > Cc: Johan De Clercq <jo...@democon.be> > Subject: Re: [OpenSIPS-Users] To-tag value in ACK > > Good day John, > it looks like your own deduction is absolutely right! > > If we talk about the SIP protocol in terms of RFC 3261, then I guess it's > clear that the acknowledgement which has a To tag, > which is different from the previously defined one (in 200 OK) of the same > dialog, should be essentially considered as out of the dialog request. > Which will not be correlated with the dialog is being established (the one in > the early stage you are talking about). > > So that, it's known - "Call-ID" + "To tag" + "From tag" gives us a full > uniqueness of certain dialog/call branch (in your case it looks like it's > only one branch though). > If you change at least a To tag in the subsequent request (in-dialog request) > for the same dialog/call branch, > then the remote side will likely fail to match it to a needed dialog > (transaction check). > > Please see this section of RFC 3261 to understand the concept: > https://tools.ietf.org/html/rfc3261#section-19.3 > > I hope I was clear enough and you find my response useful. > Have a nice day! > _______________________________________________ Users mailing list Users@lists.opensips.org http://lists.opensips.org/cgi-bin/mailman/listinfo/users
