What is camel application protocol and what is the role of cap in IMS?

Answer 1

The Customized Applications for Mobile network Enhanced Logic (CAMEL) provides the mechanisms to support services of operators, which are not covered by standardized GSM services even when roaming outside the HPLMN (Home Public Land Mobile Network).

The CAMEL feature is a network feature and not a supplementary service. It is a tool to help the network operator provide the subscribers with the operator specific services even when roaming outside the HPLMN. In this specification, the GSM Service Control Function (gsmSCF) is treated as being part of the HPLMN.

The regulatory environment in some countries may require the possibility that the gsmSCF and the HPLMN are controlled by different operators, and the gsmSCF and the HPLMN are therefore distinct entities.

In the first phase the CAMEL features support: * Mobile originated and forwarded calls * Mobile terminating calls * Any time interrogation * Suppression of announcements Note that CAMEL is not applicable to Emergency Setup (TS 12), i.e., in case an emergency call has been requested the gsmSSF is not invoked.

The CAMEL mechanism addresses especially the need for information exchange between the VPLMN (Visited PLMN) or IPLMN (Interrogating PLMN) and the HPLMN for support of operator specific services. Subscribers who have subscribed to operator specific services and therefore need the functional support of the CAMEL feature are marked in the HPLMN and VPLMN. In case a subscriber is marked to need CAMEL support, the appropriate procedures, which provide the necessary information to the VPLMN or to the HPLMN, are invoked. It is possible for the HPLMN to instruct the VPLMN or IPLMN to interact with a gsmSCF, which is controlled by the HPLMN. The CAMEL protocol is an upper layer protocol which is carried over the TCAP protocol as the data portion. In an analogy to common protocols we can parallel the TCAP to the header and the CAMEL to the rest of the decode. The message types are in the format of asn1 messages. Like most asn1 applicable protocols, the CAMEL protocol has many message types that carry a high volume of data. ABBREVIATIONS BCSM Basic Call State Model CAMEL Customized Applications for Mobile network Enhanced Logic DP Detection Point EDP Event Detection Point GMSC Gateway MSC gsmSCF GSM Service Control Function gsmSRF GSM Specialised Resource Function gsmSSF GSM Service Switching Function HLR Home Location Register HPLMN Home PLMN IPLMN Interrogating PLMN MSC Mobile service Switching Centre O-BCSM Originating Basic Call State Model O-CSI Originating CAMEL Subscription Information OSS Operator Specific Service PIC Point In Call PLMN Public Land Mobile Network SMF Service Management Function SS-CSI Supplementary Service Notification CAMEL Subscription Information T-BCSM Terminating Basic Call State Model T-CSI Terminating CAMEL Subscription Information VLR Visitor Location Register VPLMN Visited PLMN