6 About the OCECAS Architecture and Environment
This section explains the Oracle Communications Evolved Communications Application Server (OCECAS) architecture and how its components work together.
About the OCECAS Architecture
OCECAS is an application server for VoLTE services. More specifically, it is an IMS application server responsible for call control. It provides VoLTE-centric single radio voice call continuity (SRVCC) telephony voice and video communications to packet-switched IMS networks. It comes pre configured to work with border controllers such as the Oracle Communications Session Border Controller.
OCECAS is based on and uses features from both the Oracle Communications Converged Application Server (Converged Application Server) and the Oracle Fusion Middleware WebLogic application server (WebLogic server). These products are included in OCECAS.
OCECAS includes the Session Design Center GUI tool that allows an operator to customize subscriber communication sessions. The Session Design Center tool uses a simple and efficient drag-and-drop interface to create and manage session control flows.
About the OCECAS Environment
OCECAS sits on the edge of your IMS telecommunications network and serves as a multimedia (VoLTE voice and video) application server. It enables you to serve VoLTE applications on hybrid 2G/3G/IMS networks.
Figure 6-1 illustrates the OCECAS components, their relationships, and their intercommunication.
Figure 6-1 ECAS Components and Their Intercommunication
Description of ''Figure 6-1 ECAS Components and Their Intercommunication''
The top level includes the main components of the Evolved Communication Application Server: the VoLTE and VoWifi application, the Session Design Center, the default NoSQL user data repository (UDR) or ECAS Subscriber Server (ESS), the UDR views, the Charging Trigger Function (CTF), the HTTP and SIP servlet, alarms, and web services.
OCECAS also connects to the following external elements: a home subscriber server (HSS), optional third-party UDRs, an online charging system (OCS), a charging data function (CDF), a device managed by the Simple Network Management Protocol, third-party services, an optional authentication proxy (AP), and the Core Session Manager (CSM).
OCECAS connects to your IMS network through Core Session Manager using Session Border Controller (SBC). User endpoint devices (UEs) connect to ECAS through the SBC and the CSM for voice and video sessions. They connect directly to ECAS using XCAP / HTTP 1.1 to configure supported supplementary services.
Understanding the OCECAS Components
Together, the OCECAS components and technologies provide a pure IMS solution for serving applications as a Service Centralization and Continuity Application Server (SCC-AS), which provides SRVCC voice and video communication over high-bandwidth packet-switched networks.
By providing supplementary services, OCECAS offers video call support as defined in the GSMA IR.92 IMS Profile for Voice and SMS specification. ECAS also supports the User Entity (UE) registration of video as defined in the IR.92 IMS Profile for Video and SMS.
Understanding Converged Application Server
The Oracle Communications Converged Application Server (OCCAS) serves multimedia applications that use the SIP protocol. As the name implies, one of its strengths is serving converged applications that rely on various protocols and interfaces. OCCAS supports 3rd-party application development and hosting, and allows multiple applications to execute on the same incoming or outgoing request. Each application can execute separately and use its own set of rules. Each SIP servlet stores application data in a container-managed session object, so implementations persist and replicate this data to create a highly available implementation. Converged Application Server supports the JSR 359 SIP Servlet Specification, version 2.0:
Understanding WebLogic Server
Oracle WebLogic Server, which OCECAS incorporates, is a scalable, enterprise-ready Java Platform, Enterprise Edition (Java EE) application server. It is an ideal foundation for building applications based on service-oriented architecture (SOA).
The WebLogic Server implementation of the Java EE 6.0 specification provides a standard set of APIs for creating distributed Java applications. These applications can access a wide variety of services, such as databases, messaging services, and connections to external enterprise systems. WebLogic server also provides server support, such as diagnostic tools to tune performance, and the ability to capture business intelligence.
Understanding Session Border Controller
OCECAS requires a border controller and it comes pre-integrated to use Oracle Communications Session Border Controller (Session Border Controller) and Oracle Communications Core Session Manager (Core Session Manager) for this purpose. However, you can use any session border controller that your implementation requires.
Session Border Controller is a component required by OCECAS that you purchase separately. It enables service providers to deliver trusted, first-class real-time communications services across Internet Protocol (IP) network borders, including any services across IMS borders. The functions offered by Session Border Controller satisfy critical service provider requirements in five major areas: security, interoperability, reliability and quality, regulatory compliance, and revenue/cost optimization.
Understanding Core Session Manager
Core Session Manager is a product that you need to purchase separately. However most implementations require it. It is an agile session core for supporting Voice over LTE (VoLTE) services (VS-CSCF). It directs signaling flows through the network and between elements. Network Function Virtualization (NFV) allows service providers to share hardware resources efficiently across different services and customers. Core Session Manager is designed to support core session management capabilities in virtualized environments. It provides a complete set of session core functions including IP Multi-media Subsystem (IMS) Call/Session Control Functions (CSCF) and their associated 3GPP interfaces.
About Integrating OCECAS into Your Network
When you install OCECAS, you automatically get Converged Application Server and WebLogic Server technologies included in the installation.
In addition, obtain and install these Oracle Communications products:
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Core Session Manager
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Session Border Controller
Note:
Instead of purchasing Core Session Manager and Session Border Controller separately, you could purchase a copy of Oracle Communications Unified Session Manager (Unified Session Manager). Unified Session Manager contains both Core Session Manager and Session Border Controller pre-configured to work on their own hardware system as a I/S-CSCF.Once installed, configure OCECAS to connect to them.
Understanding How OCECAS Communicates
The OCECAS servers use the SIP protocol to build up and tear down calls for voice and video communications.
OCECAS uses the Diameter Sh specification to communicate with the home subscriber server (HSS) and external subscriber data repository (SPR/UDR).
The charging control function (CTF) communicates with the online charging server (OCS) using the Diameter Ro online charging specification. The CTF communicates with the charging data function (CDF) using the Diameter Rf offline charging specification.
The Core Session Manager communicates using the JSR 309 Media Control Server API Standard to communicate with media resource servers. The JSR 309 specification is available from the Java Community Process web site:
https://jcp.org/en/jsr/detail?id=309
OCECAS uses the REST and SOAP protocols to interact with 3rd-party applications and to provision subscribers.
OCECAS uses XCAP / HTTP 1.1 to communicate with a user handset to support supplementary services.
About Overload Protection
OCECAS uses the Converged Application server capabilities to provide failover protection. As shown in Figure 1-3, the OCECAS production environment uses the Converged Application Server engine and Coherence cluster (in this case, to store the Services and Change Set data). The engine controls the SIP sessions, but keep the session state and data inside the Coherence cluster. The Coherence cluster is distributed and replicated to enable failover so calls are not lost.
OCECAS is self-throttling to prevent call degradation in overload situations. Any existing sessions continue, but the platform only lets new sessions form if there is enough bandwidth to run them efficiently.