Abstract:
A method for executing a re-configuration in a self-configuring digital network after occurrence of a reconfiguration trigger, through upon detecting such trigger, communicating between various physical nodes their respective logical node identifiers and furthermore functionality informations regarding the respective node stations,  
     said method being characterized by, associated to such detecting, recognizing in a particular node such other nodes that are conducting a communication relation with said particular node, marking all logical node mappings on the various physical nodes as invalid, through said communicating of logical node identifiers establishing said reconfiguration, whilst executing communicating said functionality informations on a basis of necessity.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention relates to a method for executing a re-configuration in a self-configuring digital network after occurrence of a re-configuration trigger. A non-limiting example of such network is the Serial Bus Network IEEE 1394-1995 as discussed in International PCT Patent Application WO 00/23869. This standard allows a plug-and-play feature, and although originally intended for computer-based applications, has been introduced also into in-home consumer-electronic networks. Its prime definition level is the physical level. Various modifications and extensions to the standard have been implemented in Standards 1394A2000 and P1394.1. Still another feasible embodiment for the present invention is the USB bus standard.  
           [0002]    The above standards have been combined with the HAVI or Home Audio/Video Interoperability principles that operate on a conceptual level. This allows to combine of controller devices or nodes with controlled devices or nodes. In such combination, the user-level audio and/or video data will travel as isochronous streams, whereas control signals will travel in an asynchronous manner.  
           [0003]    Now, in such network, various incidents may cause such reconfiguration trigger signal, such as the adding or removing of a particular station, or a change of status in a particular station. However, other causes may also generate such trigger signal. The vehicle of the trigger signal may be a bus reset. In principle, all kinds of change may have occurred after such bus reset. The inventor has recognized that in general however, no change will have occurred at all. Such would then allow for executing a much simplified procedure. More in particular, the invention relates to a method as recited in the preamble of independent claim 1 hereinafter.  
           [0004]    In this respect, the abstract of the above PCT reference recites that the controlling application utilizes so-called handle objects to reconfigure objects to dynamically enumerate and represent devices that are coupled to a serial bus network after a bus reset event. During a self-identifying process, following the bus reset, information about the characteristics of the devices within the network will be received. From the self-identifying information, objects are generated that represent the various devices. Existing handle objects from a previous bus configuration are then compared to these newer objects. If a handle object would match such newer object, then a pointer value within the handle object will be changed to point to an address of the newer object. For devices that have been removed from the network, the handle object will preferably never be discarded, but is rather made invalid.  
           [0005]    Now, according to the present invention, upon occurrence of such re-configuration trigger, the logical configuration of the network must be established again. In certain circumstances, this may require an inappropriately long time, inter alia, because certain stations may need to exchange a large amount of information with one or more other stations, and/or certain stations may feature a large inherent delay before they will be fully operational again. The inventor has recognized however, that one or more parts of the network could take up their respective operations again, even if certain other stations outside the part or parts in question were still busy with recuperating. In this respect, the P1394.1 standard would even allow the forming of in-network clusters of nodes.  
         SUMMARY TO THE INVENTION  
         [0006]    In consequence, amongst other things, it is an object of the present invention to let those ones among the stations that lie in such part as recited resume their particular operations, if no obstacles against such operations would anymore exist, even if certain other stations outside the above part or parts in question were still busy with recuperating. Such inter alia would render the operation of the network much more stable, in that generally, pre-existing operational relationships between the nodes would be taken up again more or less immediately.  
           [0007]    Now therefore, according to one of its aspects the method of the present invention is characterized according to the characterizing part of claim 1. Herein, the necessity implies all that is necessary for proceeding with the ongoing operations of the network, including of coping with possible contingencies. In this respect, the reference has indeed the transmitting of the device characteristics even to physical devices with which the transmitter station had not been cooperating. Waiting until completion thereof would clearly take an inappropriately long time.  
           [0008]    The invention also relates to a system arranged for implementing a method according to the present invention as claimed in claim 6, and to an apparatus being arranged to operate as a node station in such system and as claimed in claim 7. Further advantageous aspects of the invention are recited in dependent Claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0009]    These and further aspects and advantages of the invention will be discussed more in detail hereinafter with reference to the disclosure of preferred embodiments, and in particular with reference to the appended Figures that show:  
         [0010]    [0010]FIG. 1, a logical node mapping of a network before an initial event;  
         [0011]    [0011]FIG. 2, a first logical node mapping of a network after an initial event;  
         [0012]    [0012]FIG. 3, a second logical node mapping of a network after an initial event;  
         [0013]    [0013]FIG. 4, a general binary tree network for use with the invention;  
         [0014]    [0014]FIG. 5, a flow chart of the operations executed according to a preferred embodiment. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0015]    A digital network such as, but not being limited to, a home network, will generally consist of a set of nodes interconnected by point-to-point physical links. The nodes may represent various user functionality devices, such as audio and/or video components, security cameras, household appliances, antenna disk or other external link stations, and also system-level devices, such as subaltern networks. In response to an initial event such as a bus reset, the network will be reconfigured and a new logical view of the overall status of the network must be created. For each respective node, this logical view or topology map will comprise the relevant node itself, its interconnections, and such additional functional or other information of the relevant nodes as would be appropriate. Other nodes will collect this additional information for each particular logic node as being based on the identifier of that particular node. After the reconfiguration, next to the local view, one or more of the nodes will store an overall logical view of the network. This overall view may be interrogated by other nodes according to need, until a next reconfiguration will occur. This new reconfiguration will then again cause the setting up of a new or amended overall logical view, which may then even be stored on a different node from before.  
         [0016]    The above initial event will cause an unstable situation in the network. Such unstable situation may be aggravated because various nodes will need respective different amounts of time to recover from the unstable situation, included therein a time period that is necessary for the generating or receiving of the additional information, such as functional information, on a per node basis. This functional information may by way of example include various operational parameters or interface definitions. The heavy bus traffic necessary for effecting this communication may contribute to the system instability, because in principle, each node would need to have its own, possibly partial knowledge of the logical view of the overall network. Such acquiring of the overall view may in fact be executed in that a node would interrogate the node that stores the topology map. Another feasible stratagem were that each node would itself compose such logical map view. The latter procedure may result in unnecessary waste of bandwidth due to failed transactions requests to a node that is not yet ready for communicating, or in incomplete and/or inconsistent logical views at several nodes. There will in fact be no guarantee that all preliminary logical views will be identical.  
         [0017]    The present invention applies selective topology, which allows the network to stabilize in a felicitous manner. Immediately after the event leading to the bus reset or trigger signal, the present invention will minimize the amount of communication. In fact, the inventor has recognized that it is generally not necessary to update all functionality information. The additional or functional information that uniquely identifies the physical node and its appropriate properties will always remain unchanged as long as the associated device remains in place, although its mapping on the logical identifier may be changed. It is thus proposed to only update the required information of the communicating nodes. Each node only has to store the additional information of the node or nodes it has a communcation relation with. After the initial event, the inventive idea is to take no actions on the network, but to only mark all available mappings as invalid. This marking will indicate that the stored information could still be up-to-date indeed, and that it might be re-used in the future. If the node in question has to communicate with another node marked invalid, for the first time after the initial event, the former will check whether the original mapping of the node on a particular device is still valid, through an information query to the corresponding node, and it will only selectively update the mapping according to necessity. If the mapping is invalid however, such as through removing or replacing of an apparatus, a network-wide query will be issued instead to update the mapping. The Selective Topology Mapping according to the present invention will allow the network to stabilize (it will delay the first network access), reduce the number of network accesses (use less bandwidth), and generally, increase overall efficiency.  
         [0018]    [0018]FIG. 1 illustrates a logical node mapping of a network before an initial event. For demonstration purposes, only a small-size network has been shown, but all aspects thereof would upscale immediately to a larger network. In the embodiment, device A is a video storage apparatus, device B a disc antenna station, device C a television set, and device D a camera. Many other categories of devices would be feasible, as discussed earlier. The logical node identifiers have been indicated for each device or physical node. Device A, with node identifier # 1  stores the overall logical view of the network. By way of example, Devices A and C are maintaining a video stream, for example, while running and displaying a video title. Accessing in the network is always based on the logical node identifier.  
         [0019]    Furthermore, the arrangement embodiment carries the assumption that device D will need relatively much time for recovering from the initial event, and in such interval would not be available to supply information to any of the other devices. This means that with respect to this device D, the overall network topology will not be complete before the termination of the above recovery time. However, as far as only considering the maintaining of the above video stream, the overall network could become operational much faster, i.e., as soon as devices A and C will have checked that their respective mappings have been unchanged, or rather, found out enough details on their respective whereabouts and functionality. The same would apply to the replacing of one of the two devices, as far as this replacing would not influence the mode of operation. For example, another video storage apparatus would need the same cassette and would have to be controlled in the same manner as its predecessor.  
         [0020]    [0020]FIG. 2 illustrates a first logical node mapping of a network as amended after an initial event that were to generate the described trigger signal, but with the devices located as in FIG. 1. As shown, device A has maintained its logical identifier, whereas all other devices or nodes have gotten different logical identifiers from the situation in FIG. 1.  
         [0021]    [0021]FIG. 3 illustrates a second logical node mapping of a network after a similar initial event as in FIG. 2, but for the remainder, unchanged. Again, various devices have gotten different identifiers.  
         [0022]    [0022]FIG. 4 illustrates a general binary tree network for use with the invention; no configuration with loops will be considered. In the embodiment, root node  120  has a map of the logical network. As shown, other nodes  122  through  140  are interconnected in such manner that each node has zero, one or two connected nodes in a next higher network layer. Nodes  124 ,  126 ,  134 ,  136  and  140  are leaf nodes in that they connect no node at a higher layer level. In principle, higher numbers for the interconnection multiplicity are feasible. In practice, any network size could do. The same network may also be represented by rearranging the nodes into a different configuration, leaving the various connections unchanged.  
         [0023]    [0023]FIG. 5 illustrates a flow chart of the operations executed according to an exemplary embodiment of the present invention. In block  20 , the operation starts, and all necessary hardware and software facilities are assigned. In block  22 , a Bus Reset signal is detected. Of course, such detecting may be effected through circling in a waiting loop, and this detecting would then represent a “detect-YES” exit of the loop. Now, in block  24 , all ongoing communication operations are interrupted. In block  26 , the pre-existing communication pattern is recognized by the node in question and saved in a local storage facility. This will include all ongoing communications as well as communication relations that for the moment had been inactive, but could become active if required. Next, in block  28  all mappings of the logical nodes on the physical nodes are made invalid. In block  30 , the various nodes will start undertaking to effect a new mapping pattern that would be appropriate for the overall configuration. Such undertaking may be based on the node&#39;s self-identifier assigned under the  1394  standard, and be executed first on the tree level of node itself. A particular device would first try to monopolize the associated tree level through using a timer functionality and its self-identifier, and tentatively assign to itself a logical mapping number. This number will then be broadcast on that tree level, for consent by the other connected nodes or otherwise. In block  32 , this consent (Y), or dissent (N) is detected. Next, in block  34 , the mapping is stored. To this effect, the HAVI organization must find out all changes that have been effected and retrieve the associated information, by putting the appropriate questions to all devices concerned. This operation then proceeds for the other nodes on the tree level in question, which has not been explicitly shown, and also on the other tree levels. If the mapping is unrestorable, a network-wide query is undertaken for a replacement target node for such mapping.  
         [0024]    In block  36 , the device in question will detect wether all mappings for letting the device in question resume its communication pattern have succeeded. If not yet (N), the device reverts to block  32  to find such other mapping. For reference, in the mapping patterns of FIGS.  1 - 3 , after a bus reset, two stations donot have to find any outside mapping at all, whereas the other two stations should each find only one external mapping before being able to resume operations. After completion of the local mapping (block  36  YES), the devices will transfer their functionality information to those other stations that need to know but have not yet gotten the information in question. In block  40 , a READY? detection is executed. If not, the system reverts to block  32 . Such case may for example be caused in that a subaltern mapping is still necessary. If ready, the operation of the network part is resumed. The formation of a global mapping pattern in one or more particular devices has not been illustrated in this Figure. Such storing may be undertaken in a root node that is specifically adapted, such as in FIGS.  1 - 3 . Storing in more than one node could be useful as well. Note that other various devices may already have reached the end of this flow chart, whereas other devices could still be lingering in blocks  32  or  38 .