Local communication system

Abstract

Examples of local communication systems are disclosed, based on a ring of point-to-point links, providing for transport of fixed rate synchronous, fixed rate asynchronous data and variable rate data in a flexible format. Different segments of the ring network can carry data at different bit rates, while remaining synchronised to a common frame rate and having a common control channel structure, for compatibility with earlier systems. Parallel channels are provided, either permanently or when required, for signalling errors of source data, data validity/padding, flow control. Parallel variable width channels are defined with free content (stream or packet). Null data symbols are defined for padding on a byte-by-byte basis. The allocation of capacity among variable width channels is revised block by block, and a transition period is defined to allow for ring latency. Calculations for allocation of capacity are performed during one block for the next block, locally at each source station, according to predetermined rules. Information as to bandwidth requirements is exchanged prior to the calculation via a special connection signalling channel and message format.

1 - 65 . (canceled)  
   
   
       66 . A method for allocating capacity among a plurality of desired connections over a network wherein stations of the network communicate to one another their requirements for network capacity, and each station responsible for establishing a respective connection performs a calculation to allocate to that connection a certain capacity, the calculation being performed by all such stations using a common set of rules so as to arrive at a consistent allocation of capacity between the connections.  
   
   
       67 . A method as in  claim 66 , wherein the responsible station for each connection is the source station for that connection.  
   
   
       68 . A method as in  claim 66  wherein connection signalling messages are exchanged in advance of said calculation, such that each responsible station knows the constraints imposed by at least other connections which overlap the given connection.  
   
   
       69 . A method as in  claim 66  wherein each connection carrying data from a first station designated as source for that connection to at least one second station designated as destination connection, the method further comprising: 
 generating for each connection a connection signalling message indicating a required capacity for the connection;    receiving the connection signalling messages for the plurality of connections;    determining a suitable allocation of capacity for each connection by a calculation based on the indicated required capacities and an available total capacity;    establishing each desired connection with the determined allocation,    wherein steps (b), (c), and (d) are performed independently at each first station following predetermined rules.    
   
   
       70 . A method as in  claim 68 , wherein the connection signalling messages are generated at least partially by the station designated as source for the connection.  
   
   
       71 . A method as in  claim 68 , wherein the connection signalling messages are generated at least partially by the station designated as destination for the connection.  
   
   
       72 . A method as in  claim 71 , wherein a connection signalling message is generated by the source station, modified by the destination station, and read by other source stations to obtain the necessary information for the calculation.  
   
   
       73 . A method as in  claim 72 , wherein the network is a ring network comprising a series of point-to-point links, and the modified message is received by the source station and repeated around the ring to ensure that all responsible stations have the necessary information.  
   
   
       74 . A method as in  claim 66 , wherein the allocation is re-calculated and varied from time to time.  
   
   
       75 . A method as in  claim 68 , wherein the connection signalling messages are exchanged via a dedicated channel established at least for the duration of the associated connections.  
   
   
       76 . A method as in  claim 67 , wherein the network comprises a series of station-to-station links and wherein the rules for allocating capacity to a given connection are defined so as to consider only connections which overlap the given connection.  
   
   
       77 . A method as in  claim 71 , wherein the network comprises a series of station-to-station links and wherein the rules for allocating capacity to a given connection are defined so as to consider not only connections which overlap the given connection on one or more of said links but also further connections which overlap those connections without overlapping the given connection.  
   
   
       78 . A method as in  claim 68  wherein a first rule is defined so as to ensure a minimum capacity specified in the flow control message at least for each connection of a certain priority, and further rules are specified to distribute remaining capacity among the connections.  
   
   
       79 . A method as in  claim 78  wherein said further rules take account of a maximum capacity specified in the flow control message for each connection.  
   
   
       80 . A method as in  claim 69  wherein steps (a)-(d) are repeated periodically to cause adaptive allocation of capacity between connections.  
   
   
       81 . A method as in  claim 66  wherein a plurality of stations interchange data via a network in accordance with a plurality of logical connections, each connection carrying data from a first station designated as source for that connection to at least one second station designated as destination for that connection, such data being subject to a delay at one or more intervening stations relative to a frame sequence of the ring network, the method comprising: 
 (a) defining a succession of rate control periods;    (b) determining in advance of a first rate control period a first channel width for each of the plurality of connections, the first channel width determining a maximum data rate for the corresponding connection;    (c) during said first rate control period establishing a respective channel for each connection in accordance with the determined first channel width; and    (d) during said first rate control period transmitting data for each connection via the respective channel at a rate up to said maximum data rate;    (e) determining in advance of a next rate control period a new channel width for each of the plurality of connections, the new channel width determining a new maximum data rate for the corresponding connection for said next rate control period; and    (f) repeating steps (b) to (e) for said succession of rate control periods,    wherein a rate transition period corresponding to said delay is included at the end of each rate control period and, in the event that the new channel width determined in step (e) is reduced relative to the first channel width, data is transmitted in step (d) only up to said new maximum rate during said rate transition period.    
   
   
       82 . A method as in  claim 81  wherein data transfer via the network is performed in a regular sequence of frames, each frame having a plurality of data fields for allocation to different said connections, each connection occupying the same data field or fields throughout each rate control period.  
   
   
       83 . A method as in  claim 82 , wherein each rate control period and each transition period correspond to a predetermined number of frames.  
   
   
       84 . A method as in  claim 81 , wherein the frame structure further includes a flag field for indicating the transition period.  
   
   
       85 . A method as in  claim 81 , wherein the frame structure further includes a flag field for indicating the start of each rate control period.  
   
   
       86 . A local communication system comprising a network conveying source data in variable channels, wherein capacity is allocated plurality of desired connections over a shared network medium, wherein stations of the network communicate to one another their requirements for network capacity, and each station responsible for establishing a respective connection performs a calculation to allocate to that connection a certain capacity, the calculation being performed by all such stations using a common set of rules so as to arrive at a consistent allocation of capacity between the connections.  
   
   
       87 . A system as in  claim 86 , wherein the responsible station for each connection is the source station for that connection.  
   
   
       88 . A system as in  claim 86  wherein connection signalling messages are exchanged in advance of said calculation, such that each responsible station knows the constraints imposed by at least other connections which overlap the given connection.  
   
   
       89 . A local communication system as in  claim 86  wherein a plurality of stations interchange data via a network medium, wherein capacity is allocated among a plurality of connections, each connection carrying data from a first station designated as source for that connection to at least one second station designated as destination connection, the system comprising: 
 (e) means for generating for each connection a connection signalling message indicating a required capacity for the connection;    (f) means for receiving the connection signalling messages for the plurality of connections;    (g) means for determining a suitable allocation of capacity for each connection by a calculation based on the indicated required capacities and an available total capacity;    (h) means for establishing each desired connection with the determined allocation,    wherein means (b), (c), and (d) are independently operable at each first station following predetermined rules.    
   
   
       90 . A local communications system wherein a plurality of stations interchange data via a network in accordance with a plurality of logical connections, each connection carrying data from a first station designated as source for that connection to at least one second station designated as destination for that connection, such data being subject to a delay at one or more intervening stations relative to a frame sequence of the ring network, the system comprising: 
 (a) means for defining a succession of rate control periods;    (b) means for determining in advance of a first rate control period a first channel width for each of the plurality of connections, the first channel width determining a maximum data rate for the corresponding connection;    (c) means for during said first rate control period establishing a respective channel for each connection in accordance with the determined first channel width; and    (d) means for during said first rate control period transmitting data for each connection via the respective channel at a rate up to said maximum data rate;    (e) means for determining in advance of a next rate control period a new channel width for each of the plurality of connections, the new channel width determining a new maximum data rate for the corresponding connection for said next rate control period; and    (f) means for repeating steps (b) to (e) for said succession of rate control periods,    wherein a rate transition period corresponding to said delay is included at the end of each rate control period and, in the event that the new channel width determined by means (e) is reduced relative to the first channel width, data is transmitted by means (d) only up to said new maximum rate during said rate transition period.    
   
   
       91 . A network interface circuit for use in interfacing a station to a local communication system as in  claim 86 , each station being connected between successive segments of the network, the interface comprising means operable to connect the station between first and second segments of the network.  
   
   
       92 . An apparatus for use as a station in a local communication system, the apparatus comprising at least one functional unit and a network interface circuit as in  claim 91 .  
   
   
       93 . An apparatus as in  claim 92  wherein said functional unit comprises a source or destination of audio data.  
   
   
       94 . A local communication system comprising a network conveying source data in variable rate channels, by means of a regular frame structure, each frame providing a fixed number of source data fields, wherein each field can be reserved dynamically to form part of a variable rate channel whose width varies during the life time of the relevant connection, and wherein, when a plurality of variable rate channels of non-zero width are established, each frame carries at least some data for every channel.  
   
   
       95 . A local communication system as claimed in  claim 94  wherein a plurality of stations interchange data via said network by means of said regular frame structure, and wherein a block of plural frames is established for the allocation of source data fields between a plurality of channels, the allocation being variable between blocks, wherein each successive station wishing to reserve an allocation of capacity places a header in a free field of the first frame in a given block, the header indicating directly or indirectly a next free field in accordance with the number of fields per frame reserved by the source device for its channel, each successive source station in the network inserting its header to reserve an allocation of fields for the duration of the block at the free field position indicated by said header, such that fields are allocated to channels contiguously within each frame.  
   
   
       96 . A local communication system as in  claim 95  wherein a block of plural frames is established for the allocation of source data fields between a plurality of connections, wherein each station acting as a source station for a connection reserves an allocated number of fields in each frame, and wherein each source station is responsible for removing the allocation of fields to a connection whose furthest destination station precedes the source in network position.  
   
   
       97 . A local communication system as in  claim 94  wherein each field can be reserved dynamically to form part of a fixed rate channel which uses the same fields in each frame for the duration of a connection, and at other times can be allocated to form part of a variable rate channel whose width varies during the life time of the relevant connection.  
   
   
       98 . A local communication system as in  claim 94  wherein the network is a ring network.  
   
   
       99 . A method of communication between stations in a network, wherein plural variable rate channels are established in a common frame structure, by allocating the same fields of each frame to a given channel throughout a block of frames, adapting the allocation of fields to channels for each successive block of frames.  
   
   
       100 . A method as in  claim 99  wherein there is further provided a method for allocating capacity among a plurality of desired connections over a shared network medium, wherein stations of the network communicate to one another their requirements for network capacity, and each station responsible for establishing a respective connection performs a calculation to allocate to that connection a certain capacity, the calculation being performed by all such stations using a common set of rules so as to arrive at a consistent allocation of capacity between the connections.  
   
   
       101 . A method as in  claim 99  each connection carrying data from a first station designated as source for that connection to at least one second station designated as destination connection, the method comprising: 
 generating for each connection a connection signaling message indicating a required capacity for the connection;    receiving the connection signaling messages for the plurality of connections;    determining a suitable allocation of capacity for each connection by a calculation based on the indicated required capacities and an available total capacity;    establishing each desired connection with the determined allocation,    wherein steps (b), (c), and (d) are performed independently at each first station following predetermined rules.    
   
   
       102 . A method as in  claim 101 , wherein a connection signalling message is generated by the source station, modified by the destination station, and read by other source stations to obtain the necessary information for the calculation.  
   
   
       103 . A method as in  claim 100 , wherein the connection signalling messages are exchanged via a dedicated channel established at least for the duration of the associated connections.  
   
   
       104 . A method as in  claim 100 , wherein the network comprises a series of station-to-station links and wherein the rules for allocating capacity to a given connection are defined so as to consider only connections which overlap the given connection.  
   
   
       105 . A method as in  claim 100 , wherein the network comprises a series of station-to-station links and wherein the rules for allocating capacity to a given connection are defined so as to consider not only connections which overlap the given connection on one or more of said links but also further connections which overlap those connections without overlapping the given connection.  
   
   
       106 . A method as in  claim 100  wherein a first rule is defined so as to ensure a minimum capacity specified in the flow control message at least for each connection of a certain priority, and further rules are specified to distribute remaining capacity among the connections.  
   
   
       107 . A method as in  claim 106  wherein said further rules take account of a maximum capacity specified in the flow control message for each connection.  
   
   
       108 . A method as in  claim 101  wherein steps (a)-(d) are repeated periodically to cause adaptive allocation of capacity between connections.  
   
   
       109 . A method of communication as in  claim 99  wherein a plurality of stations interchange data via a network in accordance with a plurality of logical connections, each connection carrying data from a first station designated as source for that connection to at least one second station designated as destination for that connection, such data being subject to a delay at one or more intervening stations relative to a frame sequence of the network, the method comprising: 
 (a) defining a succession of rate control periods;    (b) determining in advance of a first rate control period a first channel width for each of the plurality of connections, the first channel width determining a maximum data rate for the corresponding connection;    (c) during said first rate control period establishing a respective channel for each connection in accordance with the determined first channel width; and    (d) during said first rate control period transmitting data for each connection via the respective channel at a rate up to said maximum data rate;    (e) determining in advance of a next rate control period a new channel width for each of the plurality of connections, the new channel width determining a new maximum data rate for the corresponding connection for said next rate control period; and    (f) repeating steps (b) to (e) for said succession of rate control periods,    wherein a rate transition period corresponding to said delay is included at the end of each rate control period and, in the event that the new channel width determined in step (e) is reduced relative to the first channel width, data is transmitted in step (d) only up to said new maximum rate during said rate transition period.    
   
   
       110 . A method as in  claim 109  wherein data transfer via the network is performed in a regular sequence of frames, each frame having a plurality of data fields for allocation to different said connections, each connection occupying the same data field or fields throughout each rate control period.  
   
   
       111 . A method as in  claim 110 , wherein each rate control period and each transition period correspond to a predetermined number of frames.  
   
   
       112 . A method as in  claim 109 , wherein the frame structure further includes a flag field for indicating the transition period.  
   
   
       113 . A method as in  claim 109 , wherein the frame structure further includes a flag field for indicating the start of each rate control period.  
   
   
       114 . A network interface circuit for use in interfacing a station to a local communication system as in  claim 94 , each station being connected between successive segments of the network, the interface comprising means operable to connect the station between first and second segments of the network.  
   
   
       115 . An apparatus for use as a station in a local communication system, the apparatus comprising at least one functional unit and a network interface circuit as in  claim 114 .  
   
   
       116 . An apparatus as in  claim 115  wherein said functional unit comprises a source or destination of audio data.