Abstract: Conventional schedulers propagate entries by either polling until an entry is ready, or alternatively, by attaching a so-called “readiness time” to entries. A scheduler which recognizes the readiness time avoids consuming a parent schedule with polling, or with burdening entries with a future readiness time. The system of the present invention employs a deferral queue for deferring entries in response to pop requests from a parent schedule. The child schedule defers entries via the deferral queue when it is not ready to push an entry to the parent schedule, and sets the readiness time corresponding to the entry. Upon the expiration of the readiness time, the child schedule redetermines whether to push the deferred entry corresponding to the deferral queue or optionally to push an interim entry having since arrived. Accordingly, a child schedule receiving a pop requests retains the ability to push an entry at an earlier or later readiness time, and further retains the ability to reconsider which entry to push.

Abstract: A methodology is provided for fault detection and service restoration in a multiservice switch on a per flow basis. An ingress source transmits the same data over each of two redundant cores. An egress receiver selects on a per flow bass which core to utilize. Bi-directional flows are not necessarily grouped together. The basic approach to fault detection is to assume that the two cores are not in lock step, but that the shelves are continually monitoring link flows for control path data as well as user data. The path monitoring is accomplished using a combination of arbiter and aggregator functions found in the service shelves and core interface cards, respectively. The arbiter transmits link test cells to both cores on a per flow basis, wherein the link test cells traverse and are monitored by respective aggregators to and from each core. When an egress arbiter determines that a flow is bad, it initiates a switch to the alternative source core, from which the flow would continue.

Abstract: The present invention is a methodology for controlled switchover of unicast and multicast data flows in packet based switching system. In some cases it is advantageous to purposefully support switchover of flows from one path to the other without causing loss of data. This is termed a “controlled” or “hitless” switchover. In accordance with the present invention switchover methodology, given that an ingress arbiter device is transmitting to both cores simultaneously, it is required that the flows to both switching cores be synchronized at an aggregator level and that an egress arbiter be given time to cease receiving packets from one Core then switch over to the other Core, and continue receiving packets.

Abstract: The present invention is a core interface mechanism that permits 1:N type port protection on the core side of the switch such that core bandwidth is not wasted by the direct connection of service cards to the switching core. In an exemplary embodiment, a core interface module supports up to two active service cards and one dedicated protection service card. To provide increased efficiency and lower cost the redundant service card does not strand user bandwidth in the switch core. In an exemplary embodiment, the core interface includes a plurality of core side input and output ports for coupling to the switching core and a plurality of card side input and output ports for coupling to the service cards. A data flow switch function couples between the core side ports and the card side ports. The data flow switch function operates to complete data flow paths between the core side ports and the card side ports.

Abstract: The present invention is a methodology for controlled switchover of unicast and multicast data flows in packet based switching system. In some cases it is advantageous to purposefully support switchover of flows from one path to the other without causing loss of data. This is termed a “controlled” or “hitless” switchover. For example, it may be required to upgrade or replace a card and it is desirous to do this without taking an “Errored Second” hit at the system level. In accordance with the present invention switchover methodology, given that an ingress arbiter device is transmitting to both cores simultaneously, it is required that the flows to both switching cores be synchronized at an aggregator level and that an egress arbiter be given time to cease receiving packets from one Core then switch over to the other Core, and continue receiving packets.

Abstract: The present invention is a methodology for providing fault detection and service restoration for a multiservice switch on a per flow basis. An ingress source transmits the same data over each of the redundant cores. An egress receiver selects on a per flow basis which core to utilize. Bi-directional flows are not necessarily grouped together. That is, for a duplex path, one direction of transmission can proceed through a first core and the other direction can proceed through the other core if required. The basic approach to fault detection is to assume that the two cores are not in lock step, but that the shelves are continually monitoring link flows for control path data as well as user data. The path monitoring is done largely in dedicated hardware and the status is passed up to a local processor within a service shelf in order that recovery can proceed quickly.