Oracle Communications Unified Session Manager and IMS
The ETSI TISPAN NGN defines several subsystems that make up the NGN architecture. The model for the target NGN architecture is depicted below.
The Oracle Communications Unified Session Manager is designed to function as an integrated:
- Proxy-Call Session Control Function (P-CSCF)
- Interrogating-Call Session Control Function (I-CSCF)
- Serving-Call Session Control Function (S-CSCF)
In addition, the Oracle Communications Unified Session Manager performs many related functions. As such, the Oracle Communications Unified Session Manager is typically deployed in support of LTE and other IMS-based networks.
The functions performed by the Oracle Communications Unified Session Manager are best understood as functions of standard IMS elements. The diagram below depicts the interconnection of these elements across an IMS architecture.
High level definitions of these functions include:
- P-CSCF—The first point of contact within the IMS system for the endpoint. The P-CSCF determines whether and how to pass the traffic to the appropriate S-CSCF.
- I-CSCF—IMS passes traffic to the I-CSCF if the target S-CSCF is unknown.
- S-CSCF—Interaction with the Home Subscriber Server (HSS) determines whether and how to provide service to the endpoint.
- BGCF—The breakout gateway control function provides signaling transit to network domains external to the IMS.
- IMS-AGW—Access gateway complimenting the P-CSCF function to broaden the range of devices that can access the IMS.
- Ancilliary Access
Functions—As part of 3GPP Release 10, new interfaces and protocols have been
defined to improve mobility across LTE and 2G/3G networks and address the
latency concern from previous architectures. The enhancements to the SRVCC
system defines two logical entities located in the access network:
- ATCF—The (Access Transfer Control Function) is a signalling controller function complementing the signalling and media control roles of the P-CSCF and IMS-AGW functions in the SBC.
- ATGW—The Access Transfer Gateway is a media anchor point complementing the signalling and media control roles of the P-CSCF and IMS-AGW functions.
Refer to 3GPP specifications for complete element definitions and explanations of the functions they can or must perform. Key functions and considerations that introduce the Oracle Communications Unified Session Manager's operation are briefly discussed below.
As P-CSCF, the Oracle Communications Unified Session Manager adds traffic policing, UA functions for special SIP signaling handling, CDR generation, topology hiding, policy enforcement, and hosted NAT traversal to the 3GPP-defined P-CSCF functions. As such, the Oracle Communications Unified Session Manager can reside at the network's edge performing functions that may otherwise be performed by an SBC.
As I-CSCF, the Oracle Communications Unified Session Manager complies with 3GPP standards to perform the interrogating function and locate the proper S-CSCF for a given session.
As S-CSCF, the near the subscriber that facilitate rapid and predictable handover from LTE to circuit 2G/3G networks and update the VCC application server after the access transfer. They facilitate rapid and predictable handover from LTE to circuit 2G/3G networks and update the VCC application server after the access transfer. The combination of these new functions and improved call flow reduces the signalling hops required to handover the active voice call to the new access network complies with 3GPP standards and Oracle Communications Unified Session Manager to manage sessions. It interacts with the HSS to determine whether any given registration can reside locally, or be managed by another S-CSCF device. It also interacts with the HSS and other infrastructure components to provide applicable services within the context of a given session.
As ATCF and ATGW, Oracle Communications Unified Session Manager provides services near the subscriber that facilitate rapid and predictable handover from LTE to circuit 2G/3G networks and update the VCC application server after the access transfer. The combination of these new functions and improved call flow reduces the signalling hops required to handover the active voice call to the new access network