From a logical architecture perspective, services need not have their own control functions, as the control layer is a common horizontal layer. This is done by having a horizontal control layer that isolates the access network from the service layer. According to the 3GPP, IMS is not intended to standardize applications, but rather to aid the access of multimedia and voice applications from wireless and wireline terminals, i.e., to create a form of fixed-mobile convergence (FMC). IMS uses IETF protocols wherever possible, e.g., the Session Initiation Protocol (SIP). This vision was later updated by 3GPP, 3GPP2 and ETSI TISPAN by requiring support of networks other than GPRS, such as Wireless LAN, CDMA2000 and fixed lines. Its original formulation (3GPP Rel-5) represented an approach for delivering Internet services over GPRS. IMS was originally designed by the wireless standards body 3rd Generation Partnership Project (3GPP), as a part of the vision for evolving mobile networks beyond GSM. IMS is an architectural framework that provides such standardization. Alternative methods of delivering voice ( VoIP) or other multimedia services have become available on smartphones, but they have not become standardized across the industry. Historically, mobile phones have provided voice call services over a circuit-switched-style network, rather than strictly over an IP packet-switched network. The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem ( IMS) is a standardised architectural framework for delivering IP multimedia services. ( Learn how and when to remove this template message) ( May 2011) ( Learn how and when to remove this template message) There might be a discussion about this on the talk page.

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