UNORDERED MULTI-PATH ROUTING IN A PCIE EXPRESS FABRIC ENVIRONMENT

摘要

A method of providing unordered packet routing in a multi-path PCIe switch fabric is provided. Fabric egress port congestion is measured and distributed to all ports within a switch and to neighboring switches. An unordered route choice vector is generated by table lookup. The local congestion mask vector identifies which of these choices has local congestion. A next hop masked choice vector generated by table lookup is gated with the next hop congestion mask vectors, received from neighboring switches, to identify the choices that have next hop congestion. Congested choices are excluded by masking. If multiple choices remain at the conclusion of the masking process, then a selection is made by round-robin among the surviving choices. If no choices remain, the selection is made by round robin among the original choices. The final selection is mapped to an egress port on the switch by table lookup.

主权项

1. A method of providing unordered path routing in a multi-path PCIe switch fabric, the method comprising:
measuring port congestion on a local level receiving port congestion information of a next hop level, wherein the congestion information comprises low priority congestion information and medium priority congestion information; using a congestion feedback interconnect, such as a ring or bus, to communicate congestion within a chip, wherein only fabric ports send congestion information of the local level and an applicable next hop level to the congestion feedback ring; communicating local congestion information on said interconnect for both low priority congestion information and medium priority congestion information to a previous hop using a data link layer packet (DLLP) with a Reserved encoding; providing a masked choice vector that lists the number of paths available on the switch to route an unordered packet to a particular destination; saving the masked choice vector in a current hop destination look up table (CH-DLUT); providing a next hop masked choice vector that lists a number of choices available on the next hop per a local fabric port to route an unordered packet to a particular destination; saving the next hop masked choice vectors in a next hop destination look up table (NH-DLUT); and using the next hop masked choice vectors for a particular destination with a set of Port of Choice tables to construct a next hop masked port vector for that destination using the masked choice vector stored in the CH-DLUT and next hop masked port vector constructed from NH-DLUT and Ports of Choices tables respectively at locations corresponding to an unordered packets destination and their corresponding congestion information to determine a switching path for then unordered packet.