Method for congestion control and associated switch controller

An Ethernet switch controller comprising:

• a buffer control device, coupled to a buffer, for allocating and freeing space of said buffer;
• a plurality of port control devices, coupled to said buffer and a plurality of PHY devices, for receiving a plurality of packets from a plurality of ports via said plurality of PHY devices and requesting a space of said buffer to store said plurality of packets;
• a forwarding control device, coupled to said plurality of port control devices, for determining a destination port for each of said packets;
• a queue control device, coupled to said plurality of port control devices, said buffer control device and said forwarding control device, said queue control device comprising a plurality of queues corresponding to said plurality of ports and establishing a link in a corresponding queue of said queues corresponding to said destination port based on requests issued by said plurality of port control devices;
• and
• wherein said switch controller examines if remaining space of said buffer is less than a predetermined threshold of system congestion, if the remaining space of said buffer is less than said threshold of system congestion, then examine if a length of said corresponding queue exceeds a predetermined threshold of queue congestion and perform a proper congestion control based on said examining results.

A method of congestion control, which is used in an Ethernet switch, said switch comprising a buffer, a plurality of PHY devices and a plurality of ports, said switch receiving a plurality of packets via said plurality of ports and said buffer temporarily storing said plurality of packets, said method of congestion control comprising:

• performing a shared memory architecture for said buffer when said switch enters a normal state (XON);
• performing an equal memory partition structure for said buffer when said switch enters a state of system congestion (XOFF);
• and
• performing congestion control for all said plurality of ports when said switch enters a state of serious system congestion (ALL XOFF).