Method for accessing a non-symmetric dual-slot address table and switching apparatus using same

A method for looking up a non-symmetric dual-slot address table to transmit a packet, wherein the packet comprises a SMAC address and a DMAC address, and the non-symmetric dual-slot address table has a first entry with m slots and a second entry with n slots, m and n are integers and m is an integer multiple of n, the method comprising steps of:

• generating a hash value according to the DMAC address;
• selecting an address corresponding to the hash value for the non-symmetric dual-slot address table;
• transmitting the packet according to a destination port specified in a slot corresponding to the selected address in the first entry, when a tag of the MAC address is consistent with a tag of the SMAC address in a slot corresponding to the said selected address in the first entry;
• and
• transmitting the packet according to a source port specified in a slot corresponding to a corresponding sub-address in the second entry, when the tag and a share value of the DMAC address is consistent with a tag and a share value of a SMAC address stored in a slot corresponding to the sub-address.

A switching apparatus having a plurality of ports, for transmitting a packet having a SMAC address and a DMAC address from a source port of said plurality of ports, the switching apparatus comprising:

• a memory, having a non-symmetric dual-slot address table, wherein the non-symmetric dual-slot address table has a first entry with m slots and a second entry with n slots, m and n are integers and m is an integer multiple of n, and is used for accessing a plurality of MAC addresses;
• a writing device, for writing the SMAC address to the non-symmetric dual-slot address table, wherein a first hash value is generated according to the SMAC address;
• an first address corresponding to the first hash value from the non-symmetric dual-slot address table is selected;
• a tag and the source port for the SMAC address are written to a slot corresponding to the first address in the first entry, when the slot corresponding to the first address in the first entry is empty;
• and the first hash value is mapped to a first sub-address and a first share value when the slot corresponding to the first address in the first entry is not empty, and then a slot corresponding to the first sub-address in the second entry is selected, and the tag, the first share value and the source port of the SMAC address are written to the slot corresponding to the first sub-address in the second entry;
• and
• a transmitting device, for transmitting the packet to a destination port, wherein a second hash value is generated according to the DMAC address;
• an second address corresponding to the second hash value is selected for the non-symmetric dual-slot address table;
• the packet is transmitted according to the destination port in a slot corresponding the second address in the first entry, when a tag of the MAC address is consistent with a tag of the SMAC address in a slot corresponding to the second address in the first entry;
• and the packet is transmitted according to a source port stored in a slot corresponding to a second sub-address in the second entry, when the tag and the second share value of the DMAC address is consistent with a tag and a share value of a SMAC address stored in a slot corresponding to the second sub-address.