A modern telecommunications system often comprises one or more switched telephone networks and one or more Internet Protocol-based packet networks. These two different types of networks are interconnected by a media gateway, which acts as a translator between the two types of networks. The media gateway enables multimedia communications, such as voice and video, over multiple transport protocols end to end.
Because the media gateway connects different types of networks, one of its main functions is to convert between the different transmission and coding techniques used across the different networks. For example, a Voice-over-Internet-Protocol-capable (VoIP-capable) media gateway performs the conversion between time division multiplexed voice media that originate at a switched telephone network telecommunications terminal and VoIP datagram media that is intended for an Internet Protocol network terminal, as part of a telephone conversation between two parties; of course, the media gateway has to perform the conversion in the other direction as well. Other functions that the media gateway provides are echo cancellation, tone detection, tone generation (e.g., dual tone multi-frequency tones, etc.), and conferencing.
Since a packet stream that is received from the Internet Protocol network comprises data packets and control packets, which contain addressing information, the VoIP media gateway converts the received packets to a time division multiplexed stream while processing the control packets. The media gateway must perform the conversion in a timely manner to minimize the possibility of packet loss, which the listening party on a call might perceive. To handle all of the packets responsively and without unacceptable delay or jitter, the media gateway uses digital signal processors, which are dedicated devices that are capable of the high-speed packet processing that is required for the conversion. Each digital signal processor comprises multiple processing resources, such as processing channels, to handle multiple calls and the different conversion formats across the calls. For example, the conversion formats might be distinguished from one another by codec type, encryption algorithm, payload values, addressing information, or redundancy in the information transmitted. Protocol standards and formulas exist that govern these properties, such as G.711 and G.729 compression/decompression algorithms. Similarly, the media gateway must also perform the conversion in the other direction from a time division multiplexed stream to Internet Protocol packets in a timely manner.
One or more media gateways are controlled by a media gateway controller, which provides the call control and signaling functionality for each media gateway and across media gateways. Communication between media gateways and media gateway controllers is achieved by means of protocols such as H.248, Media Gateway Control Protocol (MGCP), and so forth. During a call initialization that involves an Internet Protocol (IP) terminal, the media gateway controller provides to the IP terminal the IP address of the media gateway resource that is handling the call. This enables the IP terminal to specify the proper destination address of the packets that it originates and to recognize the packets that are being sent to the terminal. Alternatively, instead of a call involving an IP terminal, the call could involve another media gateway that exchanges packets with the aforementioned media gateway resource that is handling the call.
On occasion, it might become necessary, under certain conditions, to remove an in-service digital signal processor from service. For example, when a technician has to diagnose or physically replace the signal processor, a technician will typically need to “busy out” the processor. What makes this difficult is that the signal processor might be handling the packet streams that correspond to one or more currently active calls between a telecommunications terminal in one type of network, such as the IP network, and a terminal in another type of network, such as the switched telephone network, described earlier. Techniques in the prior art require that the technician issue a graceful busy-out command for a selected signal processor, only to have to wait for its calls to terminate before the processor can be fully removed from service. This can be a lengthy procedure, especially if some calls that are being handled by the selected signal processor are long in duration.
What is needed is a technique to accelerate the removal from service of a signal processor at a media gateway, without some of the disadvantages in the prior art.