C.1 The need for security protection

33.2103GPPIP network layer securityNetwork Domain Security (NDS)Release 17TS

The security architecture of the IP multimedia Core Network Subsystem (IMS) is specified in 3GPP TS 33.203 [10]. 3GPP TS 33.203 [10] defines that the confidentiality and integrity protection for SIP-signalling are provided in a hop-by-hop fashion.

The first hop i.e. between the UE and the P‑CSCF through the IMS access network (i.e. Gm reference point) is protected by security mechanisms specified in 3GPP TS 33.203 [10].

The other hops, within the IMS core network including interfaces within the same security domain or between different security domains are protected by NDS/IP security mechanisms as specified by this Technical Specification.

3GPP TS 23.002 [3] specifies the different reference points defined for IMS.