Method and apparatus for backward explicit congestion notification (BECN) in an ATM network

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 modifiable issue rate unit which transmits forward information signals at different transmission rates, said issue rate unit decreasing the transmission rate in response to a presence of congestion signals and increasing the transmission rate in response to an 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 requests for congestion signals in response to congestion in the local node, said congestion signal generating means connected to said return path in said local node.
• filter means for filtering said requests and for responsively providing said congestion signals,
• 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 local nodes,
• the congestion signal generating means in one of said local nodes generates said requests for congestion signals for the virtual channel in response to congestion in said one of said local nodes and returns said congestion signals from said one of said local nodes in the reverse direction,
• 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 a plurality of wide-area sources is linked to one of a plurality of wide-area destinations through a plurality of said local networks over said local networks and said local network links.

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 a transmission rate in response to congestion signals,
• a plurality of destinations,
• a plurality of nodes, including one or more intermediate nodes, forming an asynchronous transfer mode (ATM) network connecting the sources to the destinations, each intermediate 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 requests for congestion signals in response to congestion in the intermediate node, said congestion signal generating means connected to said return path in said intermediate node,
• filter means for filtering said requests and for responsively providing said congestion signals to said return path for propagation directly to one of said sources,
• 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 intermediate nodes generates said congestion signals for the virtual channel in response to congestion in said one of said intermediate nodes and said congestion signals from said one of said intermediate nodes returns in the reverse direction without need for propagation to said destination.