%% You should probably cite rfc3665 instead of this I-D. @techreport{ietf-sipping-basic-call-flows-02, number = {draft-ietf-sipping-basic-call-flows-02}, type = {Internet-Draft}, institution = {Internet Engineering Task Force}, publisher = {Internet Engineering Task Force}, note = {Work in Progress}, url = {https://datatracker.ietf.org/doc/draft-ietf-sipping-basic-call-flows/02/}, author = {Steve Donovan and Robert Sparks and Kevin Summers and Alan Johnston and Chris Cunningham}, title = {{Session Initiation Protocol (SIP) Basic Call Flow Examples}}, pagetotal = 94, year = 2003, month = apr, day = 7, abstract = {This document gives examples of Session Initiation Protocol (SIP) call flows. Elements in these call flows include SIP User Agents and Clients, SIP Proxy and Redirect Servers. Scenarios include SIP Registration and SIP session establishment. Call flow diagrams and message details are shown.}, }