Resilient/Consistent Hashing ECMP Group

Resilient hashing helps minimize the flow remapping across equal cost multipath (ECMP) groups in a load-balanced system. Resilient hashing works in conjunction with the default static hashing algorithm. When members are added to or deleted from an ECMP group, the static hashing algorithm might remap destination paths. With resilient hashing, the chances of a flow being remapped are minimal if its path is unaffected by the ECMP group's member change. When a flow is affected by a member change, the Packet Forwarding Engine rebalances the flow by reprogramming the flow set table. Resilient hashing thus provides the following benefits: * Minimizes traffic-distribution imbalances among members of an ECMP group when members are added to or deleted from the group. * Minimizes the impact on flows bound to unaffected members when a new member is added to or an existing member is deleted from the group. In normal hash-based load balancing, with the static hashing algorithm used alone, flows are assigned to members through the mathematical mod (%) operation. Any increase or decrease in the number of group members results in a complete remapping of flows to member IDs. Resilient hashing minimizes the destination path remapping when a member in the ECMP group is added or deleted. When the flow is affected by a member change in the group, resilient hashing rebalances the flow by reprogramming the flow set table.