Not The request is denied because of the version of the Supported The request is denied because the size of the SIP 513 Message Too Large message is too great. Table 2.12. 5xx-type responses Response Description 600 Busy Everywhere The network is saturated. 603 Decline The call is refused. The SIP URI of the callee does not exist 604 Does Not Exist Anywhere anywhere. Some aspects of the session are not 606 Not Acceptable acceptable. Table 2.13. 6xx-type responses 60 VoLTE and ViLTE 2.7. SDP protocol The session description protocol (SDP) gives a description of the flow for which the establishment of the session is implemented by the SIP. The SDP message constitutes the message body attached to the SIP message. It, generally appears in the INVITE request and in the response 200 OK. The parameters which characterize the media flows are as follows: - the type of media (audio, video, data); - the transport protocol (e.g. RTP); - the format of the media (e.g. the type of codec for voice and video); - the IP address to which the media need to be transmitted; - the number of the destination port. The SDP message is a set of lines of code in the format <type>=<value>. The field <type> contains a character (Table 2.14). The content of the field <value> depends on the type. Field <type> Description Version of the protocol <value> = <0> Identifier of the origin and of the session Name of the session <value> = <-> Information about the connection Activity time of the session <valeur> = <0 0> Description of the media Complementary attribute of the media Table 2.14. Structure of SDP message Signaling Protocols 2.8. DIAMETER protocol DIAMETER protocol is used by evolved packet system (EPS), IMS and policy and charging control (PCC) networks to ensure authentication, authorization and accounting. 2.8.1. Application to EPS network Table 2.15 summarizes the DIAMETER messages exchanged over the S6a interface between the MME and HSS entities. Request Response Authentication-Information-Request (AIR) Authentication-Information-Answer