Ericsson Ericsson This document specifies a new protocol value, called 'SIP-Warning', for the Session Initiation Protocol (SIP) Reason header. The values for the name space of 'SIP-Warning' are taken from the Warning codes (warn-codes) of SIP. In addition, this document also defines one new SIP Warning code to be used in situations where User Agent Server (UAS) does not accept calls from an anonymous source.