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4.2 Characteristics

Before you start to create an application, you should first understand the following important characteristics about the CT Access Switching service. Switch Handles Terminus MVIP-95 Switch Block model

4.2.1 Switch Handles

Many functions take (or return) a switch handle. A switch handle identifies an open MVIP switching device.
To access an MVIP switching device, get a switch handle by calling swiOpenSwitch. Refer to Section 4.3, Opening a Switch Handle.
swiCloseSwitch releases a switch handle. Refer to Section 4.4, Closing a Switch Handle.

4.2.2 Terminus

A terminus is a single access point to a switch block input or switch block output. Many of the Switching service functions take one or more terminus elements as an argument.
A terminus contains a bus, a stream, and a timeslot. Component Description Bus Specifies the interface point of the switch block. Devices can reside directly on the MVIP bus. Devices can also reside on a board's local bus and may require a switch block to access the MVIP bus. Stream A grouping of timeslots that usually corresponds to a particular bit-stream of time-division multiplexed (TDM) serial data on an individual track or wire of a bus. Timeslot Specifies a particular 64kbit/second sub-division of a TDM bus stream. Timeslots number from zero (0) to n where n is stream dependent.

Component	Description
Bus	Specifies the interface point of the switch block. Devices can reside directly on the MVIP bus. Devices can also reside on a board's local bus and may require a switch block to access the MVIP bus.
Stream	A grouping of timeslots that usually corresponds to a particular bit-stream of time-division multiplexed (TDM) serial data on an individual track or wire of a bus.
Timeslot	Specifies a particular 64kbit/second sub-division of a TDM bus stream. Timeslots number from zero (0) to n where n is stream dependent.

4.2.3 MVIP-95 Switch Block Model

One of the primary reasons for the emergence of the MVIP-95 switch block model was the specification of H-MVIP.
H-MVIP is a hardware standard which defines a telephony bus compatible with the one defined in MVIP-90. H-MVIP includes additional serial data streams. The additional data streams break the MVIP-90 software switch block model. A new switch block model was created to accommodate the additional data streams. The new switch block model became part of the new MVIP-95 standard.
As illustrated in Figure 26, the MVIP-90 convention for numbering the bus signals was to number each bus signal with two numbers, one for the input side of the switch block and the other number for the output side of the switch block. For example, on the input side of the switch block, the bus signals DSo0 through DSo7 correspond to streams 0 through 7. On the output side of the switch block, the bus signals DSo0 through DSo7 correspond to streams 8 through 15.
Figure 26. The MVIP-90 Switch Block Model
As illustrated in Figure 27, this was simplified in MVIP-95 by using one number to number each bus signal, regardless of the side of the switch block. In MVIP-95, bus signals are numbered sequentially starting at 0. This allows for future expansion of the switch capacity without renumbering.
Figure 27. The MVIP-95 Switch Block Model
For example, in MVIP-95, the MVIP bus signal DSo0 (H-MVIP bus signal HDS0) is numbered 0 regardless of which side of the switch block is connected to the signal.
In MVIP-90, local devices are connected to streams 16 and higher. In MVIP-95, local devices are connected to a logical bus called a local bus. The streams they are connected to are numbered sequentially starting from 0 on the local bus.
In MVIP-95, both MVIP streams and local streams are numbered sequentially starting from 0. Therefore, there is a need to explicitly specify the bus when referring to a switch block input or output. MVIP-95 defines a new data structure called a terminus that contains a bus specifier, a stream number, and a timeslot number to refer to a switch block input and output.
Figure 28 shows the mapping of MVIP-90 streams to MVIP-95 streams.
Figure 28. Mapping of MVIP-90 Streams to MVIP-95 Streams

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