Methods and apparatus for forwarding packets in a mesh switching system

A method for forwarding packets in a switching system having a plurality of switching devices, the method comprising:

• receiving packets at a first switching device of a partial mesh topology in the switching system, the first switching device including a plurality of ports coupled respectively to a plurality of links, the plurality of links including i) at least one destination link that is directly coupled to a second switching device of the partial mesh topology in the switching system and ii) one or more source links that are coupled to a plurality of other switching devices of the partial mesh topology in the switching system, the plurality of other switching devices including i) a third switching device directly coupled to the first switching device via a first source link among the one or more source links, and ii) a fourth switching device a) directly coupled to the second switching device, b) directly coupled to the third switching device, and c) not directly coupled to the first switching device;
• selecting, based on accessing a forwarding table of the first switching device, links from among the plurality of links for transmitting packets received by the first switching device, wherein selecting the links comprises:
• selecting the at least one destination link only for packets that are to terminate at the second switching device by exiting the switching system at the second switching device, and
• selecting the one or more source links only for packets that are sourced, in the switching system, by the first switching device and that are not to terminate at the second switching device, including selecting, independent of congestion in the switching system, the one or more source links i) all packets that are sourced by the first switching device and that are not to terminate at the second switching device, ii) packets that are sourced by the first switching device and are to terminate at the third switching device, and iii) all packets that are sourced by the first switching device and are to terminate at the fourth switching device that is a) directly coupled to the second switching device and b) not directly coupled to the first switching device;
• and
• transmitting, by the first switching device, packets via ports corresponding to links selected based on accessing the forwarding table.

A switching system, comprising:

• a plurality of switching devices including a first switching device, a second switching device, a third switching device, and a fourth switching device;
• and
• an interconnect network configured to interconnect any switching device among the plurality of switching devices to any other switching device among the plurality of switching devices via ones of i) destination links, and ii) source links, each destination link directly coupling a respective first pair of switching devices and being for carrying packets that are to terminate at the respective first pair of switching devices by exiting the switching system at the respective first pair of switching devices, and each source link directly coupling a respective second pair of switching devices and being for carrying i) packets that are to terminate at the respective second pair of switching devices by exiting the switching system at the respective second pair of switching devices and ii) packets that are to terminate at one or more other switching devices different from the respective second pair of switching devices;
• wherein the destination links include at least one first destination link that directly couples the first switching device and the second switching device, and wherein the source links include one or more first source links that directly couple the first switching device with the third switching device;
• wherein the fourth switching device is i) directly coupled to the second switching device, ii) directly coupled to the third switching device, and iii) not directly coupled to the first switching device;
• the first switching device comprising a packet processor configured to access a forwarding table to select links via which packets received by the first switching device are to be transmitted by the first switching device, and to cause packets to be transmitted by the first switching device via the selected links, the forwarding table being configured to i) cause the packet processor to select the at least one first destination link only for packets that are to terminate at the second switching device by exiting the switching system at the second switching device, and ii) cause the packet processor to select the one or more first source links only for packets that are sourced, in the switching system, by the first switching device and that are not to terminate at the second switching device, including selecting, independent of congestion in the switching system, the one or more first source links for i) all packets that are sourced by the first switching device and that are not to terminate at the second switching device, ii) packets that are sourced by the first switching device and are to terminate at the third switching device, and iii) all packets that are sourced by the first switching device and are to terminate at the fourth switching device that is a) directly coupled to the second switching device and b) not directly coupled to the first switching device.