Abstract:
A method is disclosed that enables accelerating the removal from service of a signal processor at a media gateway. In accordance with the illustrative embodiment of the present invention, the media gateway receives an indication to remove one of its digital signal processors from service. Instead of waiting for all of the calls that are using the signal processor to come to an end, the media gateway proactively moves the packet streams from the signal processor to one or more other signal processors resident at the gateway. Advantageously, an effort is made to avoid having to inform the corresponding media gateway controller of the move, thereby minimizing any discontinuity in each moved packet stream.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to telecommunications in general, and, more particularly, to moving packet streams that are being handled by a first signal processor to one or more other signal processors at a media gateway. 
       BACKGROUND OF THE INVENTION 
       [0002]    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. 
         [0003]    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. 
         [0004]    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. 
         [0005]    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. 
         [0006]    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. 
         [0007]    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. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention enables accelerating the removal from service of a signal processor at a media gateway, without some of the disadvantages in the prior art. In accordance with the illustrative embodiment of the present invention, the media gateway receives an indication to remove one of its digital signal processors from service. Instead of waiting for all of the calls that are using the signal processor to come to an end, the media gateway proactively moves the packet streams from the signal processor to one or more other signal processors resident at the gateway. Advantageously, an effort is made to avoid having to inform the corresponding media gateway controller of the move, thereby minimizing any discontinuity in each moved packet stream. 
         [0009]    The media gateway of the illustrative embodiment comprises multiple signal processing units, each comprising a plurality of digital signal processors and each being uniquely addressable by an Internet Protocol address. In addition, each signal processing unit has its own address space of port numbers, each number being allocable to a packet stream that is being processed by a processing resource, such as a digital signal processing channel, on the signal processing unit. By simply reassigning each port number in use on the processor being busied out (i.e., the “affected” processor on the “affected” signal processing unit) to another processor on the same signal processing unit, the media gateway of the illustrative embodiment avoids having to inform the media gateway controller; this is because only the media gateway needs to know the new assignment of each port number, in order to properly route each packet stream. And when a processing resource is available, but not on the affected signal processing unit, the media gateway of the illustrative embodiment transmits a change request message to the media gateway controller, specifying the IP address of the new signal processing unit so that the controller can inform the IP terminal of the change in IP address. By using this two-tiered approach, the media gateway is able to accelerate the moving of the packet streams to their new processing resources while minimizing discontinuities in the packet streams. As a result, the technique in the illustrative embodiment accelerates the busying-out process of the affected digital signal processor as well. 
         [0010]    The illustrative embodiment of the present invention comprises: receiving a first indication to remove from service a first signal processor that is handling a first packet stream via a first processing resource, wherein the first processing resource is addressable by a first port number; determining, in response to receiving the first indication, whether a second signal processor is available to handle the first packet stream; and when the second signal processor is available, reassigning the first port number to a second processing resource in the second signal processor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  depicts a schematic diagram of telecommunications system  100 , in accordance with the illustrative embodiment of the present invention. 
           [0012]      FIG. 2  depicts the salient components of media gateway  101 - p  in system  100 . 
           [0013]      FIG. 3  depicts the salient components of packet processor/interface  203  at media gateway  101 - p.    
           [0014]      FIG. 4  depicts a flowchart of the salient tasks that involve removing selected digital signal processor  303 - m - n  of packet processor/interface  203  from service, in accordance with the illustrative embodiment of the present invention. 
           [0015]      FIG. 5  depicts a flowchart of the salient tasks of the thread spawned for the packet stream handled by processing resource k. 
           [0016]      FIG. 6  depicts a flowchart of the salient tasks that involve moving the packet stream from processing resource k to another processing resource at another digital signal processor of packet processor/interface  203 , in accordance with the illustrative embodiment of the present invention. 
           [0017]      FIG. 7  depicts a message flow diagram of an information exchange between media gateway  101 - 1  and message gateway controller  103 , in accordance with the illustrative embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  depicts a schematic diagram of telecommunications system  100 , in accordance with the illustrative embodiment of the present invention. Telecommunications system  100  comprises:
       i. media gateways  101 - 1  through  101 -P, wherein P is a positive integer;   ii. Internet Protocol (IP) packet network  102 ;   iii. media gateway controller  103 ;   iv. IP telecommunications terminals  104 - 1  through  104 -Q, wherein Q is a positive integer;   v. Public Switched Telephone Network (PSTN)  105 ;   vi. PSTN telecommunications terminals  106 - 1  through  106 -S, wherein S is a positive integer;   vii. local enterprise network  107 ; and   viii. analog telecommunications terminals  108 - 1  through  108 -T, wherein T is a positive integer.         
       All of the elements depicted in FIG. 1 are interconnected as shown. 
       [0027]    Media gateway  101 - p,  for p=1 through P, is a data-processing system that comprises media gateway functionality that is known in the art, acting as a translator between two types of networks in well-known fashion; as depicted, media gateway  101 - 1  acts as a translator between Internet Protocol network  102  and Public Switched Telephone Network  105  or between network  102  and local enterprise network  107 , which networks are described below. The salient components of media gateway  101 - p  are described below and with respect to  FIGS. 2 and 3 . Media gateway  101 - p  enables multimedia communications, such as voice and video, over multiple transport protocols from one terminal in one network to another terminal in another network, in part by working in concert with media gateway controller  103  to set up, maintain, and terminate calls. 
         [0028]    Because media gateway  101 - p,  including media gateway  101 - 1 , connects different types of networks, one of its main functions is to convert between the different transmission and coding techniques uses across the different networks. In accordance with the illustrative embodiment, media gateway  101 - 1  is a Voice-over-Internet-Protocol-capable (VoIP-capable) media gateway that performs the conversion between time division multiplexed voice signals that originate at a switched telephone network telecommunications terminal, such as one of terminals  106 - 1  through  106 -S, and VoIP signals that are intended for an Internet Protocol network terminal, such as one of IP terminals  104 - 1  through  104 -Q, as part of a telephone conversation between two parties. Media gateway  101 - 1  performs the conversion in the reverse direction as well (i.e., from an IP terminal to a PSTN terminal) and is able to perform bidirectional conversion for multiple calls concurrently. 
         [0029]    Media gateway  101 - 1  in the illustrative embodiment comprises voice packet-processing functionality. However, as those who are skilled in the art will appreciate, in some alternative embodiments of the present invention, media gateway  101 - p  is able to process packets that contain other types of bearer information such as video. 
         [0030]    Media gateway  101 - p  executes the tasks described below and with respect to  FIGS. 4 through 7  in supporting the functionality of the illustrative embodiment. Although a media gateway executes the tasks of the illustrative embodiment, in some alternative embodiments another type of data-processing system can be used to execute those tasks, as those who are skilled in the art will appreciate. Furthermore, in accordance with the illustrative embodiment, media gateway  101 - p  communicates with media gateway controller  103  via the H.248 protocol, but as those who are skilled in the art will appreciate, in some alternative embodiments media gateway  101 - p  can communicate in accordance with a different type of call-control protocol and can handle datagram packets other than Internet Protocol packets. In any event, it will be clear to those skilled in the art, after reading this specification, how to make and use media gateway  101 - p.    
         [0031]    As depicted, media gateway  101 - 1  is interconnected with a plurality of different types of networks, including Internet Protocol Packet Network  102 , Public Switched Telephone Network  105 , and local enterprise network  107 . Internet Protocol packet network  102  comprises one or more transmission-related nodes such as routers that are used to direct data packets from one or more sources to the correct destinations of those packets. Network  102  is capable of handling, in well-known fashion, Internet Protocol-based messages that are transmitted among two or more Internet Protocol-capable devices such as (i) one or more IP terminals  104 - 1  through  104 -Q and (ii) a media gateway such as gateway  101 - 1 , or between media gateway controller  103  and a media gateway. Public Switched Telephone Network  105  comprises one or more transmission-related nodes such as switches that are used to direct call-related signals from one or more sources to the correct destinations of those signals. Network  105  is capable of handling, in well-known fashion, either analog or digital bearer information in circuit-switched calls among two or more devices such as (i) one or more PSTN terminals  106 - 1  through  106 -S and (ii) media gateway  101 - 1 . Local enterprise network  107  provides for local distribution of analog signals, such as in an enterprise system, and comprises wiring between media gateway  101 - 1  and analog terminals  108 - 1  through  108 -T. 
         [0032]    As those who are skilled in the art will appreciate, telecommunications system  100 , and in particular media gateway  101 - p,  is capable in some alternative embodiments of handling other types of networks and other combinations of networks than depicted. Furthermore, in some alternative embodiments, each network might in turn comprise additional networks, such as cellular telephone networks and local area networks that are either wired or wireless. For example, in some embodiments network  102  might comprise a local area network (e.g., of a business enterprise, etc.), in which one or more of IP terminals  104 - 1  through  104 -Q operate. 
         [0033]    Media gateway controller  103  is a data-processing system that comprises media gateway controller functionality that is known in the art, controlling media gateways  101 - 1  through  101 -P. Media gateway controller  103  provides the call control and signaling functionality for each media gateway  101 - p,  in well-known fashion. Controller  103  communicates with media gateways  101 - 1  through  101 -P via the H.248 protocol, but as those who are skilled in the art will appreciate, in some alternative embodiments controller  103  can communicate in accordance with a different type of call-control protocol. 
         [0034]    In accordance with the illustrative embodiment, controller  103  is physically discrete from media gateways  101 - 1  through  101 -P. However, as those who are skilled in the art will appreciate, in some alternative embodiments, the functionality of controller  103  and the functionality of one or more gateways  101 - 1  through  101 -P might co-exist with each other (i.e., by sharing the same processor, memory, or other resources). In any event, it will be clear to those skilled in the art, after reading this specification, how to make and use media gateway controller  103 . 
         [0035]      FIG. 1  also depicts multiple telecommunications terminals of various types. Internet Protocol-capable endpoints such as SIP desksets and laptop-based or desktop-based softphones are represented by terminals  104 - 1  through  104 -Q. Plain Old Telephone Service (POTS) terminals, Integrated Services Digital Network (ISDN) phones, cell phones, and other PSTN-associated terminals are represented by terminals  106 - 1  through  106 -S. Analog enterprise desksets are represented by terminals  108 - 1  through  108 -T. As those who are skilled in the art will appreciate, the present invention is also applicable to other combinations of terminals than depicted. 
         [0036]      FIG. 2  depicts the salient components of media gateway  101 - p,  in accordance with the illustrative embodiment of the present invention. Media gateway  101 - p  comprises main controller  201 , memory  202 , packet processor/interface  203 , analog telephone interface  204 , switched telephone network interface  205 , and time division multiplexed (TDM) bus  206 , interconnected as shown. 
         [0037]    Main controller  201  is a general-purpose processor that is capable of controlling processor/interface  203 , interface  204 , interface  205 , and TDM bus  206 . Main controller  201  is also capable of executing instructions stored in memory  202 , reading data from and writing data into memory  202 , and executing the tasks described below and with respect to  FIGS. 4 through 7 . In some alternative embodiments of the present invention, main controller  201  might be a special-purpose processor. In any event, it will be clear to those skilled in the art, after reading this specification, how to make and use main controller  201 . 
         [0038]    Memory  202  stores the instructions and data used by main controller  201 . Memory  202  might be any combination of dynamic random-access memory (RAM), flash memory, disk drive memory, and so forth. It will be clear to those skilled in the art, after reading this specification, how to make and use memory  202 . 
         [0039]    Packet processor/interface  203  receives Internet Protocol datagram packets from packet network  102 , converts the information encoded in the packets, and forwards the converted information to TDM bus  206 , in well-known fashion. Packet processor/interface  203  also receives time division multiplexed packets from TDM bus  206 , converts the information encoded in the packets, and forwards the converted information to packet network  102 , in well-known fashion. The salient components of packet processor/interface  203  are described below and with respect to  FIG. 3 . It will be clear to those skilled in the art, after reading this specification, how to make and use packet processor/interface  203 . 
         [0040]    Analog telephone interface  204  receives signals from local enterprise network  107  and forwards the information encoded in those signals to TDM bus  206 , in well-known fashion. Interface  204  also receives signals from TDM bus  206  and forwards the information encoded in those signals to network  107 , in well-known fashion. It will be clear to those skilled in the art, after reading this specification, how to make and use analog telephone interface  204 . 
         [0041]    Switched Telephone Network interface  205  receives signals from PSTN  105  and forwards the information encoded in those signals to TDM bus  206 , in well-known fashion. Interface  205  also receives signals from TDM bus  206  and forwards the information encoded in those signals to network  105 , in well-known fashion. It will be clear to those skilled in the art, after reading this specification, how to make and use interface  205 . 
         [0042]    TDM bus  206  carries isochronous traffic between processor/interface  203  and interface  204  or  205 , in well-known fashion. It will be clear to those skilled in the art, after reading this specification, how to make and use TDM bus  206 . 
         [0043]      FIG. 3  depicts the salient components of packet processor/interface  203 , in accordance with the illustrative embodiment of the present invention. Processor/interface  203  comprises unit controller  301  and signal processing units  302 - 1  through  302 -M, wherein M is a positive integer, and are interconnected as shown. In turn, each signal processing unit  302 - m,  for m=1 through M, comprises digital signal processors  303 - m - 1  through  303 - m -N, wherein N is a positive integer. 
         [0044]    Unit controller  301  is a general-purpose processor that is capable of controlling signal processing units  302 - 1  through  302 -M. Unit controller  301  is also capable of executing the tasks described below and with respect to  FIGS. 4 through 7 . As those who are skilled in the art will appreciate, after reading this specification, in various embodiments unit controller  301  might execute all of the tasks described below or only some of those tasks with main controller  201  executing the rest, or main controller  201  instead might execute all of those tasks. Furthermore, in some alternative embodiments of the present invention, unit controller  301  might be a special-purpose processor. In any event, it will be clear to those skilled in the art, after reading this specification, how to make and use unit controller  301 . 
         [0045]    Signal processing unit  302 -m is capable of converting the packets it receives, either from packet network  102  or TDM bus  206 , into a different, predetermined format. Since a packet stream that is received, for example, from the IP packet network  102  comprises data packets and control packets, which contain addressing information, unit  302 - m  converts the received packets to a voice data stream of isochronous packets that are suitable for TDM bus  206 , while processing the control packets. Unit  302 - m  must perform the conversion in a timely manner to minimize the possibility of packet loss. To handle all of the packets responsively and without delay or jitter, unit  302 - m  uses digital signal processors  303 - m - 1  through  303 - m -N, which are dedicated devices that are capable of the high-speed packet processing that is required for the conversion. Each digital signal processor  303 - m - n  is capable of providing K processing resources such as processing channels, wherein K is a positive integer, in order to handle multiple calls and the different conversion formats across the calls. For example, each conversion format might be distinguished by a different packet size at the datagram packet side of the processing. Protocol standards exist that govern the different packet sizes, as well as other properties such as compression and decompression (as specified in G.711, G.729, and so forth), encryption, and redundancy. Similarly, unit  302 - m  must also perform the conversion in the other direction from a time division multiplexed stream to Internet Protocol packets in a timely manner, as well as control the interval between the creation and transmission of packets. 
         [0046]    Unit  302 - m  is uniquely addressable via its own Internet Protocol address. Furthermore, each processing resource of digital signal processor  303 - m - n  within unit  302 - m  is accessible by using a User Datagram Protocol (UDP) port number that has been assigned to it by its host media gateway. The UDP port numbers can be reused across signal processor units  302 - 1  through  302 -M because each signal processor unit has a different port number address space, since each unit has its own Internet Protocol address assigned to it. Therefore, each processing resource of digital signal processor  303 - m - n  is uniquely addressable by the combination of both (i) the Internet Protocol address of unit  302 - m  and (ii) the port number assigned to the resource. As those who are skilled in the art will appreciate, in some alternative embodiments, a different addressing scheme can be used—for instance, one that uses SIP addresses with port numbers or one that uses IP addresses with a resource identifier other than UDP port number. 
         [0047]    It will be clear to those skilled in the art, after reading this specification, how to make and use signal processing unit  302 - m  and its digital signal processors  303 - m - 1  through  303 - m -N. 
         [0048]      FIG. 4  depicts a flowchart of the salient tasks that involve removing selected digital signal processor  303 - m - n  from service, in accordance with the illustrative embodiment of the present invention. For illustrative purposes, digital signal processor  303 - 1 - 2  at media gateway  101 - 1  is the signal processor selected to be removed from service. As those who are skilled in the art will appreciate, some of the tasks that appear in  FIG. 4  can be performed in parallel or in a different order than that depicted. 
         [0049]    At task  401 , media gateway  101 - 1  receives an indication to remove from service digital signal processor  303 - 1 - 2 , in well-known fashion. For example, the indication could have been invoked by a technician, by another software program, by another system, and so forth. 
         [0050]    At task  402 , the variable k is initialized to  1 . The variable k is used to keep track, at any given time, of which resource k of the K processing resources in processor  303 - 1 - 2  is under consideration to have its currently-assigned packet stream moved over to a digital signal processor other than processor  303 - 1 - 2 . 
         [0051]    At task  403 , media gateway  101 - 1  checks if processing resource k is currently handling a packet stream. If the resource is handling a packet stream, task execution proceeds to task  404 . If not, task execution proceeds to task  408 . 
         [0052]    At task  404 , media gateway  101 - 1  determines whether a different digital signal processor or processors are available to handle the packet stream handled by processing resource k. The determination is based on criteria that include: i) the capabilities that are being used to handle the packet stream at processor  303 - 1 - 2 ; and ii) the capabilities of IP terminal  104 - 1  (i.e., the terminal originating the packet stream). For example, gateway  101 - 1  might preferentially identify a resource that can provide that same capability as before over a resource that cannot. As a second example, gateway  101 - 1  might use the opportunity to move the packet stream over to a “better” resource, such as a codec with more suitable encoding characteristics. In the case of the second example, gateway  101 - 1  would notify media gateway controller  103  of the change, as described below and with respect to  FIG. 7 , in order to enable the controller to accept the selection and notify the other end of the call (i.e., IP terminal  104 - 1 ). 
         [0053]    At task  405 , media gateway  101 - 1  checks if any digital signal processor is available to handle the particular packet stream currently being handled by processing resource k, independent of whether the same signal processing unit as the one handling the packet stream in question can be used. If any processor is available, task execution proceeds to task  407 . If no processor is available, task execution proceeds to task  406 . 
         [0054]    At task  406 , media gateway  101 - 1  spawns a thread that is responsible for rescheduling the search for a new resource and the moving of resource k&#39;s packet stream to that new resource. The parameters relevant to the packet stream are passed to the thread, in well-known fashion (e.g., via a memory pointer, via an operating system inter-thread communication mechanism, etc.). The operation of this thread is described below and with respect to  FIG. 5 . Meanwhile, task execution proceeds to task  408 . 
         [0055]    At task  407 , media gateway  101 - 1  moves the packet stream currently being handled by resource k to another digital signal processor. Task  407  is described below and with respect to  FIG. 6 . After task  407 , task execution proceeds to task  408 . 
         [0056]    At task  408 , media gateway  101 - 1  increments the value of the variable k. 
         [0057]    At task  409 , media gateway  101 - 1  checks if all of the packet streams have been checked at least once. If all of them have been checked, task execution proceeds to task  410 . If not, task execution proceeds back to task  403 . 
         [0058]    At task  410 , media gateway  101 - 1  continues to monitor the spawned threads from task  407  until the final packet stream has been moved. 
         [0059]    At task  411 , media gateway  101 - 1  notifies the technician that requested the removal from service in the first place that digital signal processor  303 - 1 - 2  has been removed from service. Task execution then ends. 
         [0060]      FIG. 5  depicts a flowchart of the salient tasks of the thread spawned for processing resource k&#39;s packet stream at task  406 , in accordance with the illustrative embodiment of the present invention. For pedagogical purposes, each spawned thread corresponds to exactly one processing resource k; however, as those who are skilled in the art will appreciate, the relationship between a spawned thread and a processing resource can be other than one-to-one. It will be clear to those skilled in the art which tasks depicted in  FIG. 5  can be performed simultaneously or in a different order than that depicted. 
         [0061]    At task  501  media gateway  101 - 1  spawns a thread that is responsible for rescheduling the search for a new resource and the eventual moving of resource k&#39;s packet stream to that new resource. 
         [0062]    At task  502 , the thread checks if the rescheduling of a search for a processing resource to handle resource k&#39;s packet stream is based on a call that is being handled by another digital signal processor coming to an end, thereby freeing up a processing resource at that digital signal processor. If the rescheduling is based on a call ending, task execution proceeds to task  503 . If not, task execution proceeds to task  505 . 
         [0063]    At task  503 , the thread monitors, in well-known fashion, the packet streams that media gateway  101 - 1  is handling in signal processors other than the one being busied out, to determine if a call is ending. 
         [0064]    At task  504 , the thread checks if a processing resource has become available as a result of a call having ended. If a call has ended on another digital signal processor and the available processing resource is able to satisfy the needs of processing resource k&#39;s packet stream, task execution proceeds to task  509 . If not, task execution proceeds back to task  503 . 
         [0065]    At task  505 , the thread checks if the rescheduling of a search for a processing resource is based a time interval. If the rescheduling is based on a time interval, task execution proceeds to task  506 . If not, task execution proceeds to task  508 . 
         [0066]    At task  506 , the thread waits a predetermined time interval (e.g., one minute, etc.). 
         [0067]    At task  507 , after waiting the time interval, the thread checks if a processing resource has become available. One reason as to why a processing resource might have become available is if a call has ended. Another reason is that a maintenance test (e.g., a loop-back test, etc.) was being performed and has since ended, thereby freeing up one or more resources. As those who are skilled in the art will appreciate, there can be other reasons as to why a processing resource might become available. If a processing resource has become available and the available processing resource is able to satisfy the needs of processing resource k&#39;s packet stream, task execution proceeds to task  509 . If not, task execution proceeds back to task  506 . 
         [0068]    At task  508 , the thread applies alternative criteria to rescheduling the search for a processing resource. For example, packets streams of other calls, such as those calls of a low priority, might simply be forced off of their digital signal processors to free up resources for the packet streams that have to be moved; in this case, the thread might check that another packet stream has been forced off of another signal processor. As those who are skilled in the art will appreciate, other criteria can be applied to determine when to search for an available resource. 
         [0069]    At task  509 , the thread executes the tasks that are described above and with respect to  FIG. 6 , which results in resource k&#39;s packet stream being moved to another digital signal processor. 
         [0070]    At task  510 , the thread for handling resource k&#39;s packet stream dies. 
         [0071]      FIG. 6  depicts a flowchart of the salient tasks that involve moving resource k&#39;s packet stream to another processing resource at another digital signal processor  303 - m - n,  in accordance with the illustrative embodiment of the present invention. Depending on how the tasks are invoked, the depicted tasks are subtasks of either task  407  or task  509 . As those who are skilled in the art will appreciate, some of the tasks that appear in  FIG. 6  can be performed in parallel or in a different order than that depicted. 
         [0072]    At task  601 , media gateway  101 - 1  checks if an available digital signal processor, possibly one of multiple available processors, is addressable by the same Internet Protocol address as processor  303 - 1 - 2 . If the available processor uses the same IP address, task execution proceeds to task  602 . If not, task execution proceeds to task  603 . 
         [0073]    At task  602 , media gateway  101 - 1  reassigns the UDP port number for resource k&#39;s packet stream to a different digital signal processor, such as processor  303 - 1 - 5 , within signal processing unit  303 - 1 . It will be clear to those skilled in the art how media gateway  101 - 1  assigns and reassigns port numbers dynamically. Task execution then proceeds to task  408  or task  510 , depending on how the tasks depicted in  FIG. 6  were invoked. 
         [0074]    At task  603 , media gateway  101 - 1  moves resource k&#39;s packet stream to a different signal processing unit, such as unit  302 - 2 , with a different Internet Protocol address. The messaging that is associated with task  603  is described below and with respect to  FIG. 7 . After task  603  is completed, task execution proceeds to task  408  or task  510 , depending on how the tasks depicted in  FIG. 6  were invoked. 
         [0075]      FIG. 7  depicts a message flow diagram of an information exchange between media gateway  101 - 1  and media gateway controller  103 , in accordance with the illustrative embodiment of the present invention. The events in  FIG. 7  occur as the result of task  603  having been invoked or if one or more media stream properties (e.g., the codec to be used, etc.) are changed. It will be clear to those skilled in the art which events depicted in  FIG. 7  can occur simultaneously or in a different order than that depicted. 
         [0076]    Message  701  is transmitted by media gateway  101 - 1  to media gateway controller  103 , in accordance with the illustrative embodiment of the present invention. Gateway  101 - 1  uses message  701  to request controller  103 &#39;s approval to use a different processing resource than the resource handling a particular packet stream. Message  701  specifies a different Internet Protocol address than the one being used for the packet stream, as well as a UDP port number. In some embodiments, message  701  specifies more than one IP address. 
         [0077]    Message  702  is transmitted by media gateway controller  103  to media gateway  101 - 1 , in response to message  701 . Controller  103  uses message  702  to indicate to gateway  101 - 1  that the request has been accepted and that the packet stream going forward will be associated with the new Internet Protocol address and port number. The new addressing information corresponds to a digital signal processor on a different signal processing unit at gateway  101 - 1 . Controller  103  also transmits message  703  to the endpoint associated with the packet stream, in this case Internet Protocol telecommunications terminal  104 - 1 . Terminal  104 - 1  then uses the new addressing information to determine where to send its packets going forward and which packets are the ones that the terminal should be receiving, as part of its call, given that the packet stream is being moved to a different processing resource at gateway  101 - 1 . 
         [0078]    It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. For example, in this Specification, numerous specific details are provided in order to provide a thorough description and understanding of the illustrative embodiments of the present invention. Those skilled in the art will recognize, however, that the invention can be practiced without one or more of those details, or with other methods, materials, components, etc. 
         [0079]    Furthermore, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the illustrative embodiments. It is understood that the various embodiments shown in the Figures are illustrative, and are not necessarily drawn to scale. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that a particular feature, structure, material, or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the present invention, but not necessarily all embodiments. Consequently, the appearances of the phrase “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout the Specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.