Port sets

Often, an application needs to connect multiple streams. For example, a custom server for matrix switching must connect caller A's transmit stream to caller B's receive stream and vice versa. For this reason the concept of a port set is useful. A port set is a set of one or more ports which may need to be connected to a complementary port set as a single operation. Examples of port sets containing more than one port are:

The transmit-receive pair of a telephony channel on a DTNA.
For speech recognition with barge-in and the ability to play beeps as a prompt to the caller, a speech recognition port set requires three ports:
1. A sink to accept the caller's speech.
2. A sink to accept a copy of the prompt being played to the telephony channel, which is needed to perform echo cancellation.
3. A source to play beeps to prompt the caller that a recognizer is activated.

Port sets are defined and named in a configuration file supplied as part of the software support for an adapter. You do not need to modify this file, but you may need to refer to it to understand what port sets have been defined. The custom server subroutines accept port set names as parameters. A port set may consist of a single port. A port can be a member of several port sets as it may need to be used in different combinations by different applications. Port sets to be connected must be compatible, that is they must contain a complementary number of sources and sinks.

Figure 1. Ports, port sets, sources, and sinks

This graphic shows a schematic TDM bus, divided into timeslots of 64 kbps each. A port set and a complementary port set are connected to the TDM bus by way of adapters. The port set is shown to have two source ports which connect to two sink ports in the complementary port set, and has one sink port receiving from the source port in the complementary port set. Each connection is shown taking place in its own timeslot.