Credit based flow control in an asymmetric channel environment

A method for controlling data flow from a channel service module (CSM) in an asymmetric channel environment, the method comprising:

• a CSM providing data for transmission to a physical (PHY) layer device with a channel buffer;
• a CSM transmit interface determining a traffic pattern of data flowing from the CSM to the PHY channel buffer, including:
• a first-in first-out (FIFO) threshold, which is the maximum amount of data that can be accepted at the PHY channel buffer;
• pending data in the CSM transmit interface, which is the amount of data already sent from the CSM, but not received at the PHY channel buffer;
• and,
• CSM burst size, which is the amount of data sent to the CSM transmit interface from the CSM in response to an Xon command;
• and,
• if (FIFO threshold−pending data)<CSM burst size, then sending an Xon command to the CSM requesting more data.

In a channel service module (CSM) transmit interface, a system for controlling data flow in an asymmetric channel environment, the system comprising:

• a data FIFO having a CSM interface to accept data and an output to supply data;
• a transmitter having an interface to accept data from the data FIFO and an external interface for supplying information to a physical (PHY) layer device with a channel buffer;
• an asymmetric channel controller having an external interface for sending Polling Request messages to the PHY device and receiving Polling Result messages from the PHY device concerning channel buffer capacity, and an output to supply polling information responsive to a plurality Polling messages;
• and,
• a credit flow controller having an interface connected to the asymmetric channel controller to receive the polling information, the credit flow controller determining a traffic pattern of data flowing from the CSM to the PHY channel buffer, including:
• a first-in first-out (FIFO) threshold, which is the maximum amount of data that can be accepted at the PHY channel buffer;
• the amount of pending data in the data FIFO;
• and,
• CSM burst size, which is the amount of data sent to the data FIFO in response to an Xon command;
• and,
• if (FIFO threshold−pending data)<CSM burst size, then the credit flow controller sending an Xon command to the CSM requesting more data.