Method and apparatus for closed loop, out-of-band backpressure mechanism

A computer readable medium encoded with instructions capable of being executed by a computer to establish a frame for an out-of-band backpressure bus for providing a closed loop along a datapath established between an ingress port and an egress port over a switch fabric (SF) egress port of a communication node, said medium comprising:

• instructions for establishing an egress port timeslot Tbe for carrying a congestion state indication providing the congestion state of said datapath for a data refresh interval Td;
• instructions for establishing an ingress port timeslot Tbi for carrying a count of PDUs transmitted to said SF egress port during said data refresh interval Td;
• instructions for defining a congestion state indication that includes a SF queue congestion state measuring the congestion at said egress port;
• instructions for writing additional congestion state data regarding a SF queue at said SF egress port;
• instructions for reading said additional congestion data at said egress port;
• and
• instructions for adjusting said SF queue congestion state according to said additional congestion data.

A method for improving traffic throughput along a datapath established at a communication node between an ingress port and an egress port through a switch fabric (SF) egress port, comprising:

• estimating a congestion state indication characterizing the congestion along said datapath, wherein said congestion state indication includes a SF queue congestion state that measures the congestion at said egress port;
• establishing an out-of-band bidirectional connection between said ingress port and said egress port using a backpressure bus;
• transmitting said congestion state indication to said ingress port over said backpressure bus, and transmitting traffic statistics to said egress port over said backpressure bus,
• at said SF egress port, writing on a SF ports field additional congestion state data regarding a SF queue;
• at said egress port, reading said additional congestion data from said SF ports field;
• adjusting a SF queue congestion state according to said additional congestion data;
• and
• controlling transmission of a PDU along said datapath based on said congestion state indication.