System for preserving sequential ordering and supporting idempotent commands in a ring network with busy nodes

摘要

A system for resolving packet errors and busy acknowledgments for packets in a ring network, to maintain continued packet distribution on the network with support for strongly ordered, nonidempotent commands. Each consumer node on the network maintains a record of the sequence of packets that have passed through that node, and the state of each of the packets at the time it passed through, including a record of the last known good packet and its sequence number. When a producer node detects an error condition in an acknowledgment for a packet, resends all packets beginning with the last known good packet. Each consumer node is able to process or reject the resent packets, including packets that may already have been processed, which it is aware of due to the packet and state records for all packets. Strong ordering is thus supported, since the sending order of packets can be maintained for processing due to the resends, and nonidempotent commands are supported due to the consumer nodes' ability to determine whether they have already processed a given packet, and to send an acknowledge-done reply if that is the case. A retry queueing system is used which allows the system of effectively interleave busy retry loops with an error retry loop, thus accommodating both error retries and busy retries while preserving strong sequential ordering, if desired, of the sent packets.