The IP Multimedia Subsystem (IMS) is an IP multimedia and telephony core network that is defined by 3GPP and 3GPP2 standards and organizations based on IETF Internet protocols. IMS is access independent as it supports IP to IP session over wireline IP, 802.11, 802.15, CDMA, packet data along with GSM/EDGE/UMTS and other packet data applications. IMS is a standardized reference architecture that consists of session control, connection control and an applications services framework along with subscriber and services data.
[Adapted from Lucent IP Multimedia Subsystem Overview]
