Packet route scheduling in a packet cross connect switch system for periodic and statistical packets

摘要

Routing of packets in a packet cross-connect switch is determined based on the particular type of packet, i.e., statistical or periodic, grade of service assigned to the packet, e.g., minimum delay, the actual queuing delay at output ports assigned to the particular packet destination and the status of the assigned output ports. Additionally, for periodic type packets the routing decision is also based on whether an interval is reserved for transmission of periodic packets at the assigned output ports. The routing decision is also based under certain conditions on whether or not the packet has been previously scheduled over an alternate route. The actual queuing delay at the assigned output ports is compared to predetermined delay threshold values in determining the packet route and/or whether it should be discarded. If the packet is a statistical hype and it was previously scheduled over an alternate route, it will be discarded, if it is not scheduled to be routed via a primary one of the assigned output ports and the delay at a secondary, i.e, alternate, one of the assigned output ports is greater than a predetermined re-routing delay threshold value. In a specific embodiment, the delay threshold values are selected such that typically only statistical packets are scheduled for an alternate route. Periodic packets are typically scheduled for an alternate route or discarded only for catastrophic failures.