IMS provides the framework for a common application and session control layer standardized on IP, with SIP controlling all media sessions. Disaggregating the transport, control, and application functions of the service layer from the access network enables the transmission of any type of media (i.e., voice, video or data) using any type of access method (e.g., DSL, cable, FTTx, WiMAX, 3G mobile). All call and application signaling takes the same paths, allowing a maximum convergence of services. The IMS standardization breaks down all the functions necessary to support multimedia applications and to provide standardized (open) interfaces towards application servers enabling enhanced premium services as well as the interworking with other (legacy) networks such as the PSTN/PLMN. Actual interfaces available are very much dependent on vendors' IMS implementation, also note that some interfaces are internal to the vendor's platform, and are not exposed externally. The following diagram illustrates a common deployment. The table that follows is a comprehensive list of all IMS interfaces. 
IMS Interfaces
| Cx | Reference Point between a CSCF and an HSS. | | Dx | Reference Point between an I-CSCF and an SLF | | Gm | Reference Point between a UE and a P-CSCF | | ISC | Reference Point between a CSCF and an Application Server | | Ix | Reference Point between IMS ALG and NA(P)T-PT | | Mb | Reference Point to IPv6 network services | | Mg | Reference Point between an MGCF and a CSCF | | Mi | Reference Point between a CSCF and a BGCF | | Mj | Reference Point between a BGCF and a MGCF | | Mk | Reference Point between an MGCF/IMS ALG and another BGCF | | Mm | Reference Point between a CSCF/IMS ALG and an IP multimedia network | | Mr | Reference Point between a CSCF and an MRFC | | Mw | Reference Point between n a CSCF and another CSCF | | Mx | Reference Point between a CSCF/BGCF and IMS ALG | | Sh | Reference Point between an AS (SIP-AS or OSA-CSCF) and an HSS | | Si | Reference Point between an IM-SSF and an HSS | | Ut | Reference Point between UE and an Application Server | The benefit to operators in migrating to IMS is in the reduction of costs (OPEX and CAPEX) as well as the capability to easily and quickly introduce new multimedia services that generate new revenue streams. RADCOM's IMS offering The main challenges associated with monitoring IMS environments are -
Intensive signaling flows -
Complex correlation involving multiple interfaces and segment flows -
Combination of session-based and transaction-based flows in a single end-to-end call IMS monitoring is provided as part of the Omni-Q solution. The new high performance software defined hardware probe, the R70, has been designed to specifically address the network topologies and traffic characteristics associated with an IMS environment in an NGN network. The R70 offering consists of an acquisition-analysis component and an application-host component. This offers maximal flexibility in handling various traffic combinations of signaling and media as well as flexibility in handling very high CPS (calls per second) of single or multiple protocol types. The addition of the R70 into the Omni-Q family, a distributed monitoring solution, enables cost-effective, scalable monitoring of the xCSCF-HSS cluster in addition to various other NGN elements, such as CS and MGW. Important features of Omni-Q for IMS include: -
IMS protocol suite - Advanced correlation engine to handle complex SIP-centric sessions involving proxies and B2BUA’s
- Session-based CDRs and transaction-based counters
- Customized workflows for IMS environment
- Probe characteristics:
- IP reassembly
- More than 1000 cps
- 12 Gbe links
- Simultaneous monitoring and capture mode
- Integrated forwarding capabilities
More information: VoIP Solutions R70 Network Monitor Probe Platform |
