IMS security
IMS (IP Multimedia Subsystem) is a set of specifications to offer multimedia services through IP protocol. This makes it possible to incorporate all kinds of services, such as voice, multimedia and data, on an accessible platform through any Internet connection (fixed or mobile). IMS's origin Initially defined by 4G.IP (a set of companies belonging the telecommunications sector), it was 4G (3rd Generation Partnership Project) who definitively adopted the definition of IMS as a part of the standardization 4G system in networks UMTS (Universal Mobile Telecommunications System), specified in Release 5 and 6. Architecture It can be divided into three layers: Application Where there are AS (Application Servers), the MRF (Media Resource Function) and a HSS (Home Subscriber Server). The AS used the SIP(Session Initiation Protocol) for the signaling, used in establishing multimedia sessions, such as audio and video calls over Internet. The services offered by the telephony operators are hosted and run on AS. A HSS is similar devices to the HLR of GSM technology, where the user´s credentials are stored. Control Formed by different subsystems among which is IMS core. Other important devices in this layer are the CSCF (Call Session Control Function), which includes three subsystems: P-CSCF (Proxy