A solution for vertical handover of multimedia sessions using SIP

This document proposes a solution for handling vertical handovers among different network technologies using SIP, fulfilling a set of requirements discussed in the document "Requirements for vertical handover of multimedia sessions using SIP" (draft-niccolini-sipping- siphandover-03). The solution requires a new header field (named "Handover") and a new parameter in the Via header field (named "MMID").