Abstract:
In a message delivery system wherein messages having topic portion defining a topic and a body portion containing information relating to the defined topic are delivered to subscribers based on the topics associated with the messages, the messages are placed in a queue for delivery, and in the event of congestion one or more of the messages are replaced with discard indication messages containing the topics associated with the discarded messages without the corresponding body portions.

Description:
FIELD OF THE INVENTION 
     This invention relates to data communication networks and in particular methods of notifying subscribers of message loss in message delivery systems. 
     BACKGROUND OF THE INVENTION 
     In the prior art, many message delivery systems exist which route messages between endpoints, such as between different applications. The messages may be routed to destination endpoints based on topics or topic to queue mappings. In the case of a system that routes messages based on topics an example of which is described in U.S. Pat. No. 13/357,951, the contents of which are herein incorporated by reference, there are publishing (or producing) clients that generate messages and subscribing (or consuming) clients that receive messages. When a publishing client creates a message it adds to it a topic. Destination endpoints are created by subscribing clients that have associated with them a series of subscriptions (or interests) that are used to attract messages to the subscribing application. Alternately subscriptions may be used to attract messages to a queue endpoint which one or more applications can connect to and receive messages. The topics are typically text strings that often contain sub-fields also known as hierarchical levels but, may also be numbers. Interests or subscriptions are of a similar form to the topics but, may contain regular expressions (also known as wild cards) or if the topics are in the form of numbers, the interests could be in the form of a range of numbers. The interests are gathered by the message delivery system and are used to determine which destination endpoint(s) should receive a copy of a particular message received from a publishing application in a process called matching. In the topic based message delivery system the process of matching involves comparing the topics of messages received from publishing clients to the interests gathered from subscribing clients or queues. A match to an interest is generated when the topic of the incoming messages falls within the regular expression(s) contained in the interest. 
     In a reliable message delivery system a component may become congested and find it necessary to discard one or more messages due to a lack of resources or because a queue depth exceeded a configured threshold. Prior art message delivery systems that use a brokered topology to set a discard indication flag in the message header to indicate that preceding messages were discarded. However, in this prior art there is only an indication that one or more messages were discarded without providing the topics of the discarded messages. In the case of the brokered topology, prior art systems do not scale to message delivery networks that consist of more than a single message broker (also known as a message delivery router) and do not indicate the exact topic of discarded message(s) if the subscriber interest contains a wildcard or if the subscriber endpoint has associated with it more than a single interest. In other prior art message delivery systems that use a brokerless topology subscribing clients can request a retransmission from source if a lost message is detected. If the source of the message is unable to fulfill the retransmission request, it will broadcast a dataloss advisory message to all clients. The dataloss advisory message used in the prior art brokerless messaging system contains only the identification of the source client and does not contain the topics of the messages that were lost. The dataloss advisory message must be broadcast to all clients of the brokerless message delivery system because the sender is unaware of what clients exist that may be interested in receiving the lost messages. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a method of managing congestion in a message delivery system wherein messages containing a topic portion defining a topic and a body portion containing information relating to the defined topic are delivered to subscribers based on the topics associated with the messages, comprising placing the messages in a queue for delivery; in the event of congestion in the message delivery system, discarding one or more of said messages in the queue; and replacing the discarded messages with one or more discard indication messages containing the topics associated with discarded messages without the corresponding body portions. 
     In one embodiment the discard indication messages contain only the topic portion of the original messages without the body portion, although the discard indication messages could contain the topic identified in a different manner. 
     The discard indication messages may also contain a field indicating the number of messages relating to a topic that have been discarded. For example, if four messages on a particular topic are discarded from the same queue, they could all be replaced by a discard indication message containing the topic and an indication that four messages have been discarded. 
     The discard indication messages typically have a flag set to indicate that they are unavailable for discard. 
     In another aspect the invention provides a router for use in a message delivery system wherein messages contain a topic portion defining a topic and a body portion containing information relating to the defined topic are delivered to subscribers based on the topics associated with the messages, comprising a queue for enqueing received messages for delivery; and a processor configured, in the event of congestion in the message delivery system, to: discard one or more of said messages in the queue; and replace the discarded messages with one or more discard indication messages containing the topics associated with discarded messages without the corresponding body portions of the messages. 
     It will be appreciated that the router could be implemented as a piece of specific hardware or alternatively as a software implementation on a generic server platform. 
     In yet a further aspect the invention provides storage medium storing instructions for managing congestion in a message delivery system wherein messages containing a topic portion defining a topic and a body portion containing information relating to the defined topic are placed in a queue for delivery to subscribers based on the topics associated with the messages, said instructions when executed on the processor and in the event of congestion in the message delivery system causing the processor to: discard one or more of said messages in the queue; and replace the discarded messages with one or more discard indication messages containing the topics associated with discarded messages without the corresponding body portions of the messages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  shows an example message delivery system; 
         FIG. 2  shows a block diagram of a message delivery router; 
         FIG. 3  shows series of queue states as the queue becomes congested and messages are discarded; 
         FIG. 4  shows a flow chart describing the process of generating a discard indication message; and 
         FIG. 5  shows a flow chart describing the processing of a discard indication message. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows an example message delivery system consisting of two message delivery routers  101  and  102  that are networked such that messages published to the upstream message delivery router  101  may be received by subscribers connected to a second downstream message delivery router  102 . Publishing client P 1   100  and subscribing client S 1   103  are connected to message delivery router  101  while message delivery router  102  has two connected subscribing clients S 2   104  and S 3   105 . 
     Publishing client P 1   100  is publishing messages  110  and  111  to two topics, /Animals/Lions and /Animals/Tigers respectively. Subscribing client S 1   103  has indicated to message delivery router  101  that it is interested in receiving a copy of any messages that have a topic of/Animals/Lions. There are two other subscribers S 2   104  and S 3   105  connected to the network depicted in  FIG. 1 . Subscriber S 2   104  has registered an interest in receiving messages that match the subscription/Animals/&gt;; the “&gt;” character in this case is a wild card that will match any topic with “Animals” at the first level in the topic so S 2 &#39;s interest will match messages with topics /Animals/Lions and /Animals/Tigers. Subscriber S 3   105  has registered an interest in receiving messages that match the subscription /Animals/Tigers. In order for message delivery routers  101  and  102  to function as a network, upstream message delivery router  101  will have to have some knowledge of the subscription interests of the clients attached to downstream message delivery router  102 . The subscription interests of all the subscribing clients  103 - 105  could be manually configured on each message delivery router  101 - 102  or could be propagated as the subscribing clients  103 - 105  add them by a dynamic routing protocol such as described in US Patent Application Pub. No. US 2012/0207159 A1 published Aug. 16, 2012, the contents of which are herein included by reference. 
     Upon receiving a message  110 ,  111  from publishing client P1  100 , message delivery router  101  will extract the topic of the message and attempt to match the topic to interests of subscribing clients  103 - 105  connected to the network. In the case of message  110  the topic is /Animals/Lions and that matches subscription interests from subscribing clients S 1   103  and S 2   104 . Subscribing client S 1   103  is locally attached to message delivery router  101  and a copy of the message  110 A will be placed in queue  107  to be delivered to client S 1   103 . The topic /Animals/Lions also matches a subscription interest for subscribing client S 2   104 . Subscribing client S 2   104  is not directly connected to message delivery router  101  and a copy of the message  110  will be placed in queue  106  along with other messages to be delivered to subscribing clients S 2   104  and S 3   105  that are connected to the downstream message delivery router  102 . When message delivery router  102  receives a message from queue  106  it must perform its own matching process to determine the locally attached subscribing clients with interests that match the topic of the message. In the case of message  110  with a topic of /Animals/Lions, the message delivery router  102  will detect a matching interest for subscribing client S 2   104  and will place a copy of the message  110 B in queue  108  for delivery to subscriber S 2   104 . 
     A very similar procedure is performed for message  111  with a topic of /Animals/Tigers. In the case of message  111 , there are no local subscribers with a matching interest connected to message delivery router  101  however; both subscribing clients S 2   104  and S 3   105  connected to downstream message delivery router  102  have registered matching interests. Message delivery router  101  will detect a matching interest for subscribing clients connected to the downstream message delivery router  102  and will place a copy of message  111  into queue  106  for delivery to message delivery router  102 . Upon receiving a copy of message  111  downstream message delivery router  102  will perform its own matching process and will detect matching interests for subscribing clients S 2   104  and S 3   105 . Upon detecting matching interests message delivery router  102  will place a copy of the message  111 B in queue  108  for delivery to subscriber S 2   104  and a copy of the message  111 A in queue  109  for delivery to subscriber S 3   105 . 
     The level of service provided by the network of  FIG. 1  is reliable, also known as best effort; meaning that if either of the message delivery routers  101 ,  102  becomes congested it may choose to discard messages as a method of relieving congestion. Prior art message delivery systems may set a flag in the header of the next message placed in a subscriber queue  107 - 109  after a message from that queue was discarded to indicate to the subscriber that one or more messages was lost. This method has some limitations for example queues that are destined for other message delivery routers contain messages for more than one subscribing client such as queue  106  in  FIG. 1 . When a discard occurs, the discard flag is set on the next message in queue  106 , which may be destined for delivery to a different set of clients (subset or superset) than the discarded message. As a result, setting the discard flag for messages from queue  106  is meaningless to the downstream message delivery router  102 . Therefore, prior art systems typically do not set the discard flag when messages are discarded from queue  106 . The result is that the discard flag will not be set for messages sent to subscribing clients connected to the downstream message delivery router  102  and subscribing clients  104 ,  105  connected to the downstream message delivery router will be unaware that messages were discarded by an upstream message delivery router on flows that they are subscribed to. A second limitation of the prior art method is in the case where a subscribing client is interested in more than one topic; in this case the subscriber queue will contain messages with more than one topic. An example of a subscriber queue containing messages with more than one topic is subscriber queue  108  containing messages for subscribing client S 2   104 . Subscriber queue  108  contains messages with topic /Animals/Lions and /Animals/Tigers. If a message in subscriber queue  108  was discarded, message delivery router  102  could set the discard flag in the header of the next message placed in queue  108  to indicated to the subscribing client  104  that messages were discarded but the subscribing client would not be able to detect which topic(s) the discarded message(s) were for. 
     Using the techniques of the present invention, when a message is discarded the discarded message is replaced in a queue by a special discard indication message that contains only the topic of the discarded message. Typically, with the present invention, more than one message would be discarded when congestion is detected, to make room in the queue for newly arrived messages, in which case the discard indication message would contain the topic of each of the messages that was discarded. The discard indication messages would themselves be tagged as discard ineligible meaning that they should not be discarded by any downstream routers. The discard indication messages in a subscriber queue would be delivered to subscriber clients so that the subscribing client could use it to determine the topic(s) of the message(s) that were discarded. If messages are discarded from a queue containing messages destined for subscribing clients connected to a downstream message delivery router then the discard indication message will be delivered to the downstream message delivery router. Upon receiving a discard indication message a message delivery router will remove the topic(s) contained within and match them to subscription interests of downstream and local subscribing clients. The discard indication message will be placed in queue to any destinations detected during the matching process. 
       FIG. 2  shows an example implementation of a message delivery router  200 . In the example implementation there is a network interface  202 , used by the message delivery router  200  to communicate with publisher or subscriber client systems. The network interface  202  implements a standard networking protocol such as Ethernet or Infiniband; messages received from publishing clients or sent to subscribing clients must pass through the network interface  202 . Any communication received from a client must traverse the system bus  201  and be placed in random access memory or RAM  203 , as it is known in the art. The system bus  201  is a communication path inside the message delivery router  200  for which many protocols exist and are well known in the art. The system bus  201  could be implemented using PCI express or other protocol or a combination of different bus protocols connected by components know in the art as bridges and switches. Any communications to or from a client must exist in RAM  203  and is transferred to or from the network interface  202  by direct memory access or DMA as it is known in the art. Communication from clients such as messages from publishing clients once in RAM  203  can be inspected by a micro processor  204 . The microprocessor  204  is shown as a single entity however, there may be multiple microprocessors present in the system, each of which may contain multiple processing cores. The microprocessor  204  is responsible for receiving all stimuli from clients and generating all responses. The optional matching engine  205  is a hardware engine designed to offload the microprocessor  204  of the task of matching. In many implementations the matching is performed by the microprocessor  204 . Message delivery systems deliver messages received from publishing clients to subscribing clients that have indicated an interest in receiving messages that match a certain criteria. In many implementations the publishing clients add a meta-data topic to the message; this topic is compared by the message delivery system  200  to interests that it has collected from subscribing clients in a process called matching. The process of matching can be an onerous task when there are large topic sets and large numbers of interests. In these situations the application of a hardware engine designed specifically to perform the task such as the matching engine  205  can enhance system performance. 
     The techniques of the present invention will be further described by the following examples with reference to  FIG. 1 . In the first example messages will be discarded from subscriber queue  107 . Publishing client P 1   100  sends a message  110  with a topic of /Animals/Lions to the message delivery router  101 . The message delivery router  101  matches the message topic to interests collected from subscribing clients  103 - 105 . Matching interests are detected for locally connected subscriber S 1   103  and remote subscribing clients connected to downstream message delivery router  102 . Based on the matching interests detected a copy of the message  110  must be placed in queue  106  for delivery to subscribing clients connected to the downstream message delivery router  102  and in queue  107  for locally connected subscribing client S 1   103 . Upon trying to place a copy of the message  110  in queue  107  the message delivery router  101  detects congestion. In order to relieve this condition the message delivery router  101  must discard one or more messages from the congested queue  107 . In a typical implementation a message delivery router would discard the oldest messages in the queue to relieve congestion; however the techniques of the present invention can be applied to messages discarded from any position in the queue. Within the scope of the present invention the message delivery router  101  may use any method to determine how many messages it needs to discard in order to relieve the congested condition. For example the message delivery router may choose to discard the newest messages in the queue or may choose to discard messages from random locations or if the queue contains messages with more than one topic the message delivery router may choose to discard all messages with a topic that matches the current message. In discarding the messages the message delivery router  101  generates a discard indication message containing the topics of the discarded messages. The discard indication message replaces the discarded messages in queue  107  to be delivered to subscribing client S 1   103 . When the discard indication message is delivered to the subscribing client S 1   103 , the subscribing client S 1   103  will inspect any topics included in the message to see exactly which topic flows experienced message loss. As an optimization to conserve resources the message delivery router  101  may choose to only include unique topics in the discard indication message. In the present example queue  107  contains only messages with topic /Animals/Lions and if the message delivery router choose to discard more than one message from queue  107  of the same topic (/Animals/Lions), the resulting discard indication message would only contain a single topic. As a further optimization the discard indication message could also contain a count associated with each unique topic indicating how many messages with this topic were discarded. 
     In the second example messages will be discarded from queue  106  containing messages destined to subscribing clients connected to downstream message delivery router  102 . Note that queue  106  contains messages destined for subscribing clients S 2   104  and S 3   105  connected to downstream message delivery router  102  and will contain messages with topic /Animals/Lions and /Animals/Tigers. Publishing client P 1   100  sends a message  111  with a topic of /Animals/Tigers to message delivery router  101 . The message delivery router  101  matches the topic of the message to interests collected from subscribing clients  103 - 105 ; detecting matches to interests from subscribing clients S 2   104  and S 3   105  connected to downstream message delivery router  102 . Upon detecting the matching interests the message delivery router attempts to place a copy of the message  111  into queue  106  containing messages destined to the downstream message delivery router  102 . Message delivery router  101  is currently experiencing congestion and must take action to relieve the condition by discarding messages from queue  106  which with the addition of the new message  111  has exceeded its maximum depth threshold. In discarding messages the message delivery router  101  as in the previous example will generate a discard indication message and place the topics of the discarded messages in it. The discard indication message will replace the discarded messages in queue  106  and will be delivered to downstream message delivery router  102 . The discard indication message will be marked as discard ineligible so the message will not be discarded by downstream message delivery router  102  if it too is congested. Upon receiving the discard indication message downstream message delivery router  102  will extract any topics contained within and match them to interests collected from subscribing clients  103 - 105 ; for any matching interests detected a copy of the discard indication message will be enqueued to those destination that registered the matching interest. In the present example queue  106  contains messages with topics /Animals/Lions and /Animals/Tigers and for the purposes of the present example it is assumed that messages with both topics were discarded by the upstream message delivery router  101 . The topics contained in the discard indication message are /Animals/Tigers and/Animals/Lions. Topic /Animals/Tigers matches subscription interests for subscribing clients S 2   104  and S 3   105 , and so a copy of the discard indication message will be placed in queues  108 - 109 . Subscribing client S 2   104  also has a matching subscription for /Animals/Lions however the discard indication message previously placed in queue  108  already has the topic /Animals/Lions in it and it is not necessary to enqueue a second copy of the discard indication message. When delivered to the subscribing clients S 2   104  and S 3   105  the discard indication message will indicate that messages with topics /Animals/Tigers and /Animals/Lions were discarded; in this case by an upstream message delivery router  101 . 
     As an optimization in cases where multiple topics are contained in the discard indication message, the message delivery router could modify the content of the individual copies of the discard indication message(s) placed in the subscriber queue(s) to only contain topics for which that subscribing client had indicated a matching interest. In the previously described second example the discard indication message placed in queue  109  contained topics /Animals/Tigers and /Animals/Lions even though subscribing client S 3   105  is only interested in receiving messages of topic /Animals/Tigers. The copy of the discard indication message placed in queue  109  could be modified to contain only topic /Animals/Tigers for which subscribing client S 3   105  has registered an interest. 
     Another possible optimization is in the case where the message delivery router decided that it must discard additional messages from a queue before it has delivered the previous discard indication message. In this case the message delivery router could discard additional messages and instead of creating a new discard indication message it could amend the previous one as if all the message discards were completed in a single operation. 
       FIG. 3  shows an example queue that is experiencing congestion. As new messages are added to the queue it becomes necessary to discard messages and insert a discard indication message or amend an existing discard indication message.  FIG. 3( a )  describes a state of the queue in which it has two messages, message A  300  and message B  301 . Both messages  300 ,  301  have the same topic  302 , /Animals/Tigers. In addition to a topic  302 , each message has a message body  303 . For illustrative purposes the queue has a maximum depth of two messages; in most real applications the queue depth would be much larger.  FIG. 3( b )  describes a state of the queue where a third message C  306  has arrived and been added to the queue. At this point the queue is congested because its maximum depth of two has been exceeded and some action will be required to relieve the congested condition. In order to relieve the congestion the message delivery router discards message A  300  and message B  301 . In the present example the message delivery router chooses to discard the two oldest messages in the queue (or from the head). Within the scope of the present invention the message delivery router could choose to discard as many messages as deemed necessary to relieve the congestion and from any location in the queue. The resultant state of the queue is shown in  FIG. 3( c ) . In place of the two discarded messages  300  and  301  is a discard indication message  317 . The discarded messages  300  and  301  both had the same topic. /Animals/Tigers and so the discard indication message lists only one topic  318 /Animals/Tigers. The discard indication message  317  also contains an optional count field  319  associated with each topic. The count field  319  is a count of how many message with that topic were discarded. In the present example, queue state as depicted in  FIG. 3( c )  the count field  319  of discard indication message  317  indicates that two messages with topic  318 /Animals/Tigers were discarded. 
       FIG. 3( d )  depicts the state of the queue after two additional messages  307 ,  308  have been added to the queue. The maximum depth of the queue has once again been violated and the message delivery router must take action to relieve the congestion condition. Once again the message delivery router chooses to discard the two oldest messages in the queue. Message C  306  has a topic of /Animals/Lions and message D  308  has a topic of /Animals/Tigers. The discard indication message  317  from the previous discard operation has not yet been delivered and remains in the queue; the message delivery router may choose to amend the existing discard indication message  317  rather than creating a second. The resultant state of the queue is depicted in  FIG. 3( e ) . The queue now contains one message  307  and a modified discard indication message  312 . The discard indication message  317  (depicted in  FIG. 3( d ) ) has been modified to reflect the newly discarded messages; the modified version is shown as  312  in  FIG. 3( e ) . Discarded message C  306  had topic /Animals/Lions which did not previously exist in the discard indication message  312  (as shown in the previous state of  FIG. 3( d ) ) necessitating the addition of a second topic entry  315 . Associated with the topic entry  315 /Animals/Lions is the optional count field  320  with a value of one, indicating that a single message with topic /Animals/Lions was discarded. Message D  300  was also discarded with a topic of /Animals/Tigers. Topic /Animals/Tigers was present in the discard indication message  317  of the previous queue state (depicted in  FIG. 3( d ) ). As such, it does not need to be added again. Instead, the count field  314  is updated to three from the previous value of two indicating that an additional message with topic /Animals/Tigers was discarded. 
     The previously described discard indication message format does not convey any information about the order of arrival of the discarded messages. Other discard indication message formats are possible within the scope of the present invention for example if the order of arrival of the discarded messages was important to the subscriber applications then the topic of every message discarded could be included in the discard indication message in the order in which the discarded messages arrived. In the previously described method only unique topics were included in the discard indication message and a count field was used to indicate how many messages with that topic were discarded. If applications only care which topics experienced message loss and not how many messages were discarded then the count field can be omitted as an additional space savings. 
       FIG. 4  is a flow chart that describes the processing that takes place on a message delivery router after receiving a new message from a publishing client or from an upstream message delivery router. Processing starts at step  401  when the message delivery router receives a new message. In step  402  the message delivery router extracts the topic from the message it just received and matches it to subscriber interests. For each subscriber interest that matched a copy of the message is enqueued to the endpoint associated with the matching interest at step  403 . In the description of the present invention it is assumed that the queues are implemented as link lists however other queue structures are possible. With a linked list implementation it is possible to add anew link to the queue even if the queue is at its maximum length; subsequent operations such as discarding messages are used to return the queue to a state where it is not exceeding its maximum length. With some other queue implementations such as a hardware FIFO it is not possible to exceed the maximum depth and it would be necessary to free up space in the queue before the new message could be added. Note that the subscriber associated with a matching interest may be a downstream message delivery router if the subscriber is not locally connected the selected queue will be a queue leading to a downstream message delivery router. In the case a copy of the message will be placed in queue to a downstream message delivery router, the message is only queued once for all downstream destinations which may be multiple subscribing clients or other further downstream routers. As the message delivery router is placing a copy of the message into queue, it will check to see if it is experiencing congestion in step  404 . If the queue is experiencing congestion then in step  405  the message delivery router will discard one or more messages to relieve the congestion. In step  406  a discard indication message will be generated containing the topics of the messages that were previously discarded in step  405  or optionally an existing discard indication message already in the queue may be amended to include information about the newly discarded messages. The discard indication message will replace the discarded messages in queue in step  407 . Note that the message delivery router may detect multiple queues that are experiencing congestion in which case it may be necessary to repeat steps  405 - 407  for each congested queue. If the endpoint is not found to be congested at step  404  then proceed directly to the end of the process at step  407 . 
       FIG. 5  is a flow chart that describes the processing that takes place on a downstream message delivery router upon receiving a discard indication message from an upstream message delivery router. Starting at step  501  where the downstream message delivery router receives a discard indication message. At step  502  the downstream message delivery router extracts the topic(s) from the discard indication message and matches them to subscriber interests in a process similar to that of matching a newly published message. Note that a discard indication message may contain multiple topics if the upstream message delivery router chose to discard multiple messages. For any matching subscriber interests that are detected a copy of the discard indication message is placed in the queue associated with the matching interest at step  503 . Optionally at step  503  the message delivery router could modify copies of the discard indication message to contain only topics that are of interest to the subscriber associated with the queue to which the copy of the discard indication message is added. At step  504  a copy of the discard indication message is sent to the subscribing client who may use the discard indication message to determine exactly which topic flows have experienced message loss. Note that if the downstream message delivery router is also an upstream router to other further downstream route (s) then matches may be detected in step  502  that are for subscriber endpoints connected to another router. In this case processing of the discard indication message proceeds as described in  FIG. 4  step  403  for these endpoints. Processing completes at step  505 . 
     It will be appreciated by persons skilled in the art that many variants of the invention are possible. 
     It should be appreciated by those skilled in the art that any block diagrams herein represent functional blocks of illustrative circuitry embodying the principles of the invention, which may in practice be implemented in software modules using digital signal processing techniques. 
     For example, the invention may be implemented in a processor through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), and non volatile storage. Other hardware, conventional and/or custom, may also be included. 
     All references mentioned above are herein incorporated by reference.