8.4. IMS Network Architecture – A Closer Look
In this section, we take a closer look at the IMS network architecture and describe the individual functional entities. Here, we focus on entities that reside on OSI layer 5 and higher, i.e. applications on top of TCP/IP or UDP/IP. Hence, IP infrastructure is not shown. DNS is not specifically shown either, as DNS is required for all IP services and therefore forms part of the IP infrastructure.
As the IMS network standard is continuously evolving, it is recommended that the reader check the latest release of 3GPP IMS specifications (see
8.4.1. Core Network Entities
18.104.22.168. Serving CSCF
The Serving Call State Control Function (S-CSCF) is the main SIP session control node in an IMS network. ...