A redirect server is a user agent server that generates 3xx (redirection) responses to requests it gets, directing the consumer to Get hold of an alternate set of URIs. A redirect server allows proxy servers to immediate SIP session invitations to external domains. Registrar[edit] SIP is usually a text-centered protocol http://buzzgram.de/die-evolution-der-kommunikation-eine-einfuhrung-in-sip-trunking-voip-handys-softphones-und-voip-telefonanlagen/