Method and apparatus for reactive congestion control in an asynchronous transfer mode (ATM) network

Claim 2

A communication system having reactive congestion control comprising, a plurality of sources, each source including a modifiable issue rate unit which transmits forward information signals at different transmission rates in response to congestion signals, said issue rate unit decreasing the transmission rate in response to congestion signals, a plurality of destinations, one or more nodes forming an asynchronous transfer mode (ATM) network connecting the sources to the destinations, each node including, a forward path for transfer of information in a forward direction toward a destination through the network, a return path for returning congestion signals in a reverse direction through the network toward a source, congestion signal generating means for generating congestion signals in response to congestion in the node, said network having a plurality of virtual channels where, for each virtual channel, one of said plurality of sources is linked to one of said plurality of destinations through said network by linking forward paths from one or more nodes, and wherein said issue rate unit transmits forward information signals at different transmission rates in response to congestion signals over the virtual channel, said one of said plurality of destinations is linked to said one of said plurality of sources through said network by linking return paths from said one or more nodes, the congestion signal generating means in one of said nodes generates said congestion signals for the virtual channel in response to congestion in said one of said nodes and transmits said congestion signals, in the reverse direction without need for propagation to said one of said plurality of destinations. over said return paths to said modifiable issue rate unit in said source.

Claim 3

The communication system of claim 1 wherein said issue rate unit increases the transmission rate in response to the absence of congestion signals.

Claim 4

The communication system of claim 1 wherein the transmission interval for a congestion signal returning from a congested node to the source is less than the interval between information signals transmitted over the virtual channel whereby the issue rate unit reactively responds to modify the transmission rate to reduce congestion.

Claim 5

The communication system of claim 1 wherein the transmission interval for a congestion signal returning from a congested node to the source is less than ten intervals between information signals transmitted over the virtual channel whereby the issue rate unit reactively responds to modify the transmission rate to reduce congestion.

Claim 6

The communication system of claim 1 wherein the processing time required to generate a congestion signal at each node is much less than the transmission interval for a congestion signal returning from a congested node to the source.

Claim 7

The communication system of claim 1 wherein said issue rate unit has means for decreasing said transmission rate exponentially in response to a congestion signal.

Claim 8

The communication system of claim 6 wherein said issue rate unit, after decreasing said transmission rate, has means for increasing said transmission rate exponentially in response to the absence of a congestion signal.

Claim 9

The communication system of claim 7 wherein the rate of increasing said transmission rate is less than the rate of decreasing said transmission rate.

Claim 10

The communication system of claim 1 wherein said forward information is fragmented into cells, each cell including a virtual channel identifier, and wherein each node includes a switching element, each switching element including, a switch fabric, a plurality of port controllers interconnected by said switch fabric, each of said port controllers including, an input controller, an output controller, congestion detection means for detecting congestion in the node, reversing means for copying a cell, having a virtual channel identifier, from the forward path to the return path to thereby generate a congestion signal on said return path.

Claim 11

The communication system of claim 9 wherein said reversing means includes reverse marker means for marking copied cells with a return path indicator whereby return cells are distinguished from forward cells.

Claim 12

The communication system of claim 9 wherein each of said port controllers includes selector means for selecting cells from one virtual channel for the forward path or from another virtual channel for the return path.

Claim 13

The communication system of claim 11 wherein said selector means grants priority to cells from the return path whereby congestion signals are given priority in the network.

Claim 14

The communication system of claim 9 wherein said forward paths include queues for storing cells in the forward direction, each of said queues including means for providing a queue-level signal, as a function of the fullness of the queue, to form the congestion signal.

Claim 15

The communication system of claim 1 wherein said forward information is fragmented into cells, each cell including a virtual channel identifier, and wherein each node includes a switching element, each switching element including, a switch fabric, a plurality of port controllers interconnected by said switch fabric, each port controller connected to a communication link and each port controller including, an input controller for said link including a translator for receiving the virtual channel identifier of incoming cells on the link and responsively translating the input virtual channel identifier of incoming cells to an output virtual channel identifier of outgoing cells for another link for another port controller connected to said switch fabric, an output controller for said link, congestion detection means for detecting congestion in the node, reversing means for copying a cell, having a virtual channel identifier, from the forward path to the return path to thereby generate a congestion signal on said return path, said reversing means connecting said output virtual channel identifier to be reverse translated to said input virtual channel identifier whereby the virtual channel identifiers for cells in the forward path and in the return path over the link are the same.

Claim 16

The communication system of claim 14 wherein said port controller includes one or more queues connected in parallel for queueing cells for the forward path and the return path of a link, said queues providing queue-level signals indicating the fullness of the queues and including selection means for selecting cells from said queues.

Claim 17

The communication system of claim 15 wherein said selector means grants priority to cells from the return path whereby congestion signals are given priority in the network.

Claim 18

The communication system of claim 14 wherein said reversing means includes reverse marker means for marking copied cells with a return path indicator whereby return cells are distinguished from forward cells.

Claim 19

The communication system of claim 14 wherein each of said port controllers includes selector means for selecting cells from one virtual channel for the forward path or from another virtual channel for the return path.

Claim 20

The communication system of claim 14 wherein said selector means grants priority to cells from the return path whereby congestion signals are given priority in the network.

Claim 21

The communication system of claim 14 wherein said forward paths include queues for storing cells in the forward direction, each of said queues including means for providing a queue-level signal, as a function of the fullness of the queue, to form the congestion signal.

Claim 22

A wide-area communication system having local reactive congestion control comprising, a plurality of local communication systems, each local communication system including, a plurality of local sources, each local source including a local modifiable issue rate unit which transmits forward information signals at different transmission rates, said issue rate unit decreasing the transmission rate in response to the presence of congestion signals and increasing the transmission rate in response to the absence of congestion signals, a plurality of local destinations, one or more local nodes forming an asynchronous transfer mode (ATM) local network connecting the sources to the destinations, each local node including, a forward path for transfer of information at different selectable transmission rates in a forward direction toward a destination through the network, a return path for returning congestion signals in a reverse direction through the network toward a source, congestion signal generating means for generating congestion signals in response to congestion in the local node, said network having a plurality of virtual channels where, for each virtual channel, one of said plurality of local sources is linked to one of said plurality of local destinations through said local network by linking forward paths from one or more local nodes, and wherein said issue rate unit transmits forward information signals at different transmission rates in response to congestion signals over the virtual channel, said one of said plurality of local destinations is linked to said one of said plurality of local sources through said network by linking return paths from said one or more nodes, the congestion signal generating means in one of said local nodes generates said congestion signals for the virtual channel in response to congestion in said one of said local nodes and transmits said congestion signals over said return paths, in the reverse direction without need for propagation to said one of said plurality of destinations, to said local modifiable issue rate unit in said source, one or more wide-area sources connected to one of said local networks, one or more wide-area destinations connected to another one of said local networks, a plurality of local network links interconnecting two or more local networks to form a wide-area network, said wide-area network having a plurality of virtual channels where, for each virtual channel, one of said plurality of wide-area sources is linked to one of said plurality of wide-area destinations through a plurality of said local networks over said local networks and said local network links.

Claim 23

A wide-area communication system having local reactive congestion control comprising, a plurality of local communication systems, each local communication system including, a plurality of local sources, each local source including a local modifiable issue rate unit which transmits forward information signals at different transmission rates, said issue rate unit decreasing the transmission rate in response to the presence of congestion signals and increasing the transmission rate in response to the absence of congestion signals, a plurality of local destinations, one or more local nodes forming an asynchronous transfer mode (ATM) local network connecting the sources to the destinations, each local node including, a forward path for transfer of information at different selectable transmission rates in a forward direction toward a destination through the network, a return path for returning congestion signals in a reverse direction through the network toward a source, congestion signal generating means for generating congestion signals in response to congestion in the local node, said network having a plurality of virtual channels where, for each virtual channel, one of said plurality of local sources is linked to one of said plurality of local destinations through said local network by linking forward paths from one or more local nodes, and wherein said issue rate unit transmits forward information signals at different transmission rates in response to congestion signals over the virtual channel, said one of said plurality of local destinations is linked to said one of said plurality of local sources through said network by linking return paths from said one or more nodes, the congestion signal generating means in one of said local nodes generates said congestion signals for the virtual channel in response to congestion in said one of said local nodes and transmits said congestion signals over said return paths, in the reverse direction without need for propagation to said one of said plurality of destinations, to said local modifiable issue rate unit in said source, one or more wide-area sources connected to one of said local networks, one or more wide-area destinations connected to another one of said local networks, a plurality of local network links interconnecting two or more local networks to form a wide-area network, said wide-area network having a plurality of virtual channels where, for each virtual channel, one of said plurality of wide-area sources is linked to one of said plurality of wide-area destinations through a plurality of said local networks over said local networks and said local network links.

Claim 24

The wide-area communication system of claim 21 wherein the transmission interval for a congestion signal returning from a congested local node to the local source is short thereby enabling the issue rate unit to reactively modify the transmission rate and thereby reduce congestion in the wide-area communication system.

Claim 25

The wide-area communication system of claim 21 wherein the transmission interval for a congestion signal returning from a congested local node to the local source is less than the interval between information signals transmitted over the virtual channel whereby the issue rate unit reactively responds to modify the transmission rate to reduce congestion in the wide-area communication system.

Claim 26

The wide-area communication system of claim 21 wherein the transmission interval for a congestion signal returning from a congested local node to the local source is less than ten intervals between information signals transmitted over the virtual channel whereby the issue rate unit reactively responds to modify the transmission rate to reduce congestion in the wide-area communication system.

Claim 27

The wide-area communication system of claim 21 wherein the processing time required to generate a congestion signal at each node is much less than said transmission interval for a congestion signal.

Claim 28

The wide-area communication system of claim 21 wherein said issue rate unit has means for decreasing said transmission rate exponentially in response to a congestion signal.

Claim 29

The wide-area communication system of claim 26 wherein said issue rate unit, after decreasing said transmission rate, has means for increasing said transmission rate exponentially in response to the absence of a congestion signal.

Claim 30

The wide-area communication system of claim 27 wherein the rate of increasing said transmission rate is less than the rate of decreasing said transmission rate.

Claim 31

The wide-area communication system of claim 21 wherein said forward information is fragmented into cells, each cell including a virtual channel identifier, and wherein each node includes a switching element, each switching element including, a switch fabric, a plurality of port controllers interconnected by said switch fabric, each of said port controllers including, an input controller, and an output controller, congestion detection means for detecting congestion in the node, reversing means for copying a cell, having a virtual channel identifier, from the forward path to the return path to thereby generate a congestion signal on said return path.

Claim 32

The wide-area communication system of claim 29 wherein said reversing means includes reverse marker means for marking copied cells with a return path indicator whereby return cells can be distinguished from forward cells.

Claim 33

The wide-area communication system of claim 29 wherein each of said port controllers includes selector means for selecting cells from one virtual channel for the forward path or from another virtual channel for the return path.

Claim 34

The wide-area communication system of claim 31 wherein said selector means grants priority to cells from the return path whereby congestion signals are given priority in the network.

Claim 35

The wide-area communication system of claim 29 wherein said forward paths include queues for storing cells in the forward direction, each of said queues including means for providing a queue-level signal, as a function of the fullness of the queue, to form the congestion signal in response to the queue-level signal.

Claim 36

The wide-area communication system of claim 21 wherein said forward information is fragmented into cells, each cell including a virtual channel identifier, and wherein each node includes a switching element, each switching element including, a switch fabric, a plurality of port controllers interconnected by said switch fabric, each port controller connected to a communication link and each port controller including, an input controller for said link including a translator for receiving the virtual channel identifier of incoming cells on the link and responsively translating the input virtual channel identifier of incoming cells to an output virtual channel identifier of outgoing cells for another link for another port controller connected to said switch fabric, an output controller for said link, congestion detection means for detecting congestion in the node, reversing means for copying a cell, having a virtual channel identifier, from the forward path to the return path to thereby generate a congestion signal on said return path, said reversing means connecting said output virtual channel identifier to be reverse translated to said input virtual channel identifier whereby the virtual channel identifiers for cells in the forward path and in the return path over the link are the same.

Claim 37

The wide-area communication system of claim 34 wherein said port controller includes one or more queues connected in parallel for queueing cells for the forward path and the return path of a link, said queues providing queue-level signals indicating the fullness of the queues and including selection means for selecting cells from said queues.

Claim 38

The wide-area communication system of claim 35 wherein said selector means grants priority to cells from the return path whereby congestion signals are given priority in the network.

Claim 39

The wide-area communication system of claim 34 wherein said reversing means includes reverse marker means for marking copied cells with a return path indicator whereby return cells can be distinguished from forward cells.

Claim 40

The wide-area communication system of claim 34 wherein each of said port controllers includes selector means for selecting cells from one virtual channel for the forward path or from another virtual channel for the return path.

Claim 41

The wide-area communication system of claim 34 wherein said selector means grants priority to cells from the return path whereby congestion signals are given priority in the network.

Claim 42

The wide-area communication system of claim 34 wherein said forward paths include queues for storing cells in the forward direction, each of said queues including means for providing a queue-level signal, as a function of the fullness of the queue, to form the congestion signal in response to the queue-level signal.

Claim 43

A communication system of one or more virtual channels having reactive congestion control comprising, a plurality of sources, each source including a modifiable issue rate unit which transmits forward information signals at different transmission rates in response to congestion signals, said issue rate unit transmitting, for each of one or more channels, at a maximum-channel-peak-cell-rate in the absence of congestion and at a rate below the maximum-channel-peak-cell-rate for each channel experiencing congestion, a plurality of destinations, one or more nodes forming an asynchronous transfer mode (ATM) network connecting sources to destinations, each node including, a forward path for transfer of information in a forward direction toward a destination through the network, a return path for returning congestion signals in a reverse direction through the network toward a source, congestion signal generating means for generating congestion signals in response to congestion in the node, for each of one or more virtual channels in the network, one of said plurality of sources is linked to one of said plurality of destinations through said network by linking forward paths from one nodes, and wherein said issue rate unit transmits forward information signals at different transmission rates in response to congestion signals over the virtual channel, said one of said plurality of destinations is linked to said one of said plurality of sources through said network by linking return paths from said one or more nodes, the congestion signal generating means in one of said nodes generates said congestion signals for the virtual channel in response to congestion in said one of said nodes and transmits said congestion signals over said return paths, in the reverse direction without need for propagation to said one of said plurality of destinations, to said modifiable issue rate unit in said source.

Claim 44

A communication system of one or more virtual channels having reactive congestion control comprising, a plurality of sources, each source including a modifiable issue rate unit which transmits forward information signals at different transmission rates in response to congestion signals, said issue rate unit transmitting, for each of one or more channels, at a maximum-channel-peak-cell-rate in the absence of congestion and at a rate below the maximum-channel-peak-cell-rate for each channel experiencing congestion, a plurality of destinations, one or more nodes forming an asynchronous transfer mode (ATM) network connecting sources to destinations, each node including, a forward path for transfer of information in a forward direction toward a destination through the network, a return path for returning congestion signals in a reverse direction through the network toward a source, congestion signal generating means for generating congestion signals in response to congestion in the node, for each of one or more virtual channels in the network, one of said plurality of sources is linked to one of said plurality of destinations through said network by linking forward paths from one nodes, and wherein said issue rate unit transmits forward information signals at different transmission rates in response to congestion signals over the virtual channel, said one of said plurality of destinations is linked to said one of said plurality of sources through said network by linking return paths from said one or more nodes, the congestion signal generating means in one of said nodes generates said congestion signals for the virtual channel in response to congestion in said one of said nodes and transmits said congestion signals over said return paths, in the reverse direction without need for propagation to said one of said plurality of destinations, to said modifiable issue rate unit in said source.

Claim 45

A multiple issue rate source for use in a communication system of one or more virtual channels having reactive control where said system includes, one or more of said multiple issue rate sources, a plurality of destinations, one or more nodes forming an asynchronous transfer mode (ATM) network connecting sources to destinations, each node including, a forward path for transfer of information in a forward direction toward a destination through the network, a return path for returning control signals in a reverse direction through the network toward a source, control signal generating means for generating control signals in response to congestion in the node, for each of one or more virtual channels in the network, one of said plurality of sources is linked to one of said plurality of destinations through said network by linking forward paths from one or more nodes, said one of said plurality of destinations is linked to said one of said plurality of sources through said network by linking return paths from said one or more nodes, the control signal generating means in one of said nodes generates said control signals for the virtual channel in response to congestion in said one of said nodes and transmits said congestion signals over said return paths to said modifiable issue rate unit in said source, said multiple issue rate source comprising, a modifiable issue rate unit having means to transmit forward information signals at different transmission rates in response to said control signals, said issue rate unit having an output for transmitting, for each of one or more virtual channels, at a maximum-channel-peak-cell-rate in the absence of a control signal and at a rate below the maximum-channel-peak-cell-rate for each channel providing a control signal.

Claim 46

A multiple issue rate source for use in a communication system of one or more virtual channels having reactive control where said system includes, one or more of said multiple issue rate sources, a plurality of destinations, one or more nodes forming an asynchronous transfer mode (ATM) network connecting sources to destinations, each node including, a forward path for transfer of information in a forward direction toward a destination through the network, a return path for returning control signals in a reverse direction through the network toward a source, control signal generating means for generating control signals in response to congestion in the node, for each of one or more virtual channels in the network, one of said plurality of sources is linked to one of said plurality of destinations through said network by linking forward paths from one or more nodes, said one of said plurality of destinations is linked to said one of said plurality of sources through said network by linking return paths from said one or more nodes, the control signal generating means in one of said nodes generates said control signals for the virtual channel in response to congestion in said one of said nodes and transmits said congestion signals over said return paths to said modifiable issue rate unit in said source, said multiple issue rate source comprising, a modifiable issue rate unit having means to transmit forward information signals at different transmission rates in response to said control signals, said issue rate unit having an output for transmitting, for each of one or more virtual channels, at a maximum-channel-peak-cell-rate in the absence of a control signal and at a rate below the maximum-channel-peak-cell-rate for each channel providing a control signal.

Claim 47

The multiple issue rate source of claim 42 wherein said issue rate unit includes means for increasing the transmission rate, after decreasing said transmission rate, in response to the absence of control signals.

Claim 48

The multiple issue rate source of claim 42 wherein said issue rate unit has means for decreasing said transmission rate exponentially in response to a control signal.

Claim 49

The multiple issue rate source of claim 42 wherein said issue rate unit, after decreasing said transmission rate, has means for increasing said transmission rate exponentially in response to the absence of a control signal.

Claim 50

The multiple issue rate source of claim 45 wherein the rate of increasing said transmission rate is less than the rate of decreasing said transmission rate.

Claim 51

A multiple issue rate source for use in a communication system where the communication system has one or more multiple issue rate sources connected through one or more channels to a plurality of destinations and has control signal generating means for generating control signals for the channels for reactively controlling the transmission rates over the channels, said multiple issue rate source comprising, a modifiable issue rate unit having means to transmit information signals at different transmission rates in response to control signals, said issue rate unit having an output for transmitting, for each of one or more channels, at a maximum-channel-peak-cell-rate or at a rate below the maximum-channel-peak-cell-rate as a function of the control signals for each channel and wherein said issue rate unit has means for decreasing said transmission rate exponentially as a function of the control signals.

Claim 52

A multiple issue rate source for use in a communication system where the communication system has one or more multiple issue rate sources connected through one or more channels to a plurality of destinations and has control signal generating means for generating control signals for the channels for reactively controlling the transmission rates over the channels, said multiple issue rate source comprising, a modifiable issue rate unit having means to transmit information signals at different transmission rates in response to control signals, said issue rate unit having an output for transmitting, for each of one or more channels, at a maximum-channel-peak-cell-rate or at a rate below the maximum-channel-peak-cell-rate as a function of the control signals for each channel and wherein said issue rate unit has means for decreasing said transmission rate exponentially as a function of the control signals.

Claim 53

A multiple issue rate source for use in a communication system where the communication system has one or more multiple issue rate sources connected through one or more channels to a plurality of destinations and has control signal generating means for generating control signals for the channels for reactively controlling the transmission rates over the channels, said multiple issue rate source comprising, a modifiable issue rate unit having means to transmit information signals at different transmission rates in response to control signals, said issue rate unit having an output for transmitting, for each of one or more channels, at a maximum-channel-peak-cell-rate or at a rate below the maximum-channel-peak-cell-rate as a function of the control signals for each channel and wherein said issue rate unit, after decreasing said transmission rate, has means for increasing said transmission rate exponentially in response as a function of the absence of the control signals.

Claim 54

A multiple issue rate source for use in a communication system where the communication system has one or more multiple issue rate sources connected through one or more channels to a plurality of destinations and has control signal generating means for generating control signals for the channels for reactively controlling the transmission rates over the channels, said multiple issue rate source comprising, a modifiable issue rate unit having means to transmit information signals at different transmission rates in response to control signals, said issue rate unit having an output for transmitting, for each of one or more channels, at a maximum-channel-peak-cell-rate or at a rate below the maximum-channel-peak-cell-rate as a function of the control signals for each channel and wherein said issue rate unit, after decreasing said transmission rate, has means for increasing said transmission rate exponentially in response as a function of the absence of the control signals.

Claim 55

The multiple issue rate source of Claim 48 wherein the rate of increasing said transmission rate is less than the rate of decreasing said transmission rate.