Credit recovery in a credit based flow control system

A credit based flow control system comprising:

• a credit head end and a credit queue end;
• the credit head end comprising:
• a receiver receiving a credit return message including a returned credit number;
• a credit counter initializing a credit count to be equal to a initial credit count of credits, each credit representing a permission to send a unit of data from the credit head end to the credit queue end;
• the credit counter decrementing the credit count for every unit of data sent from the credit head end to the credit queue end and incrementing the credit count by a returned credit number received from the credit queue end;
• a sender sending a credit check message to the credit queue end;
• a credit owed counter initialized with a number of outstanding credits;
• and decremented by the returned credit number;
• the credit queue end comprising:
• a queue receiving units of data from the credit head end;
• a credit return sender sending the credit return message including the returned credit number, the returned credit number indicating a number of units of data removed from the queue;
• wherein a loss or a gain in the credits used in the credit based flow control system is determined using the credit owed counter and the returned credit number;
• and the credit count is adjusted based on the loss or the gain.

A machine readable storage medium comprising a plurality of instructions for causing a computer to:

• assign an initial credit count of credits in a credit head end, each credit representing a permission to send a unit of data from the credit head end to a credit queue end;
• initialize a credit count to be equal to the initial credit count;
• decrement the credit count for every unit of data sent from the credit head end to the credit queue end;
• send a credit return message including a returned credit number, the returned credit number indicating a number of units of data removed from a queue at the credit queue end;
• increment the credit count in the credit head end by the returned credit number received from the credit queue end;
• send a credit check message from the credit head end to the credit queue end;
• initialize a credit owed counter with a number of outstanding credits;
• receive, at the credit head end, the credit return message including the returned credit number;
• decrement the credit owed counter based on the returned credit number;
• determining a loss or a gain in the credits used in the credit based flow control system using the credit owed counter and the returned credit number;
• and
• adjust the credit count based on the loss or the gain.