Service Architecture for Traditional Telephone Network

The service architecture for the traditional telephone network (wireline and wireless) is defined around the Intelligent Network (IN) [FAY96]. IN is a conceptual architecture that separates the call control from the service execution. Figure 2.1 shows a simplified IN architecture. (In reality, there are more IN entities than depicted in Figure 2.1, but for our discussion, the ones depicted in the figure suffice.) Subscribers use telephonic devices that are connected to a telephone switch called the Service Switching Point (SSP). An SSP, in turn, is connected to yet other IN entities via a packet network called Signaling System 7 (SS7). The most important IN entity is the Service Control Point (SCP), which is added to the call by the SSP. An SCP is a general-purpose computer that hosts and executes the service logic for a subscriber. The service logic can invite other IN devices into the call; for instance, if a service requires the caller to interact with a voice response system, an Intelligent Peripheral is dynamically added to the call.

Legend:

IP Intelligent Peripheral SCP Service Control Point SDP Service Data Point SCEP Service Creation

Environment Point SMP Service Management Point

SSP Service Switching Point

Singnaling (SS7)

-Transport (Media)

----Management Provisioning and Control

Singnaling (SS7)

-Transport (Media)

----Management Provisioning and Control

Scp Sdp Smp

Figure 2.1 Traditional telephone network architecture.

The service logic can also access data pertinent to each subscriber stored in a specialized database called the Service Data Point (SDP).

When a call is originated on the telephone network, the caller's SSP arranges for the SCP to be brought into the call. The SCP then executes the service logic, depending on the services subscribed to by the caller. This process is repeated on the callee's side as well; the callee's SSP on receiving a call setup request arranges for an SCP to be brought into the call, and so on.

Services themselves are created in a general-purpose computer called the Service Creation Environment Point (SCEP). A service in IN is created by chaining reusable components called Service Independent Building Blocks (SIBs); many well-known SIBs exist, such as number analysis or adding new devices into a call. Service logic programmers employ a SIB palette to drag and drop individual SIBs to compose a service. Once a service is thus created, it is deployed at the SCP using the Service Management Point (SMP), which is yet another general-purpose computer through which service management and provisioning are performed.

The cellular telephone network also uses IN to create and deploy services. The process of executing a service in the cellular network is similar to its wireline equivalent; the crucial difference is that in a cellular network, there are more entities involved in providing a service. A set of databases — home location register and visitor location register — track the subscriber and store the services associated with the subscriber. Authentication servers authenticate and authorize a cellular endpoint, and other infrastructure (base stations, mobile switching centers) provide radio access networks and the capability to connect to other cellular subscribers or to the wireline telephone network.

More information on IN is provided in [FAY96].

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