Abstract: A method and system for providing delay bound and prioritized packet dropping are disclosed. The system limits the size of a queue configured to deliver packets in FIFO order by a threshold based on a specified delay bound. Received packets are queued if the threshold is not exceeded. If the threshold is exceeded, a packet having a precedence level less than that of the precedence level of the received packet is dropped. If all packets in the queue have a precedence level greater than that of the packet received, then the received packet is dropped if the threshold is exceeded.

Abstract: Priority propagation is achieved in the context of a rate-based scheduling hierarchy. Priority traffic is not delayed by non-priority traffic by more than the duration required for transmission of the maximum packet length at the physical interface speed. Multiple sibling priority levels are supported. To achieve these objectives, the scheduling hierarchy tree is divided into sub-trees corresponding to non-priority traffic and the different levels of priority. At each scheduling decision, a packet is selected from the highest priority non-empty sub-tree. Scheduling decisions within each sub-tree exploit the usual rate-based scheduling method but without priority propagation. When a packet from a priority sub-tree is chosen, scheduling state in the non-priority sub-tree is updated.

Abstract: A method and system for providing delay bound and prioritized packet dropping are disclosed. The system limits the size of a queue configured to deliver packets in FIFO order by a threshold based on a specified delay bound. Received packets are queued if the threshold is not exceeded. If the threshold is exceeded, a packet having a precedence level less than that of the precedence level of the received packet is dropped. If all packets in the queue have a precedence level greater than that of the packet received, then the received packet is dropped if the threshold is exceeded.

Abstract: Eligible entries are scheduled using an approximated finish delay identified for an entry based on an associated speed group. One implementation maintains schedule entries, each respectively associated with a start time and a speed group. Each speed group is associated with an approximated finish delay. An approximated earliest finishing entry from the eligible schedule entries is determined that has an earliest approximated finish time, with the approximated finish time of an entry being determined based on the entry's start time and the approximated finish delay of the associated speed group. The scheduled action corresponding to the approximated earliest finishing entry is then typically performed. The action performed may, for example, correspond to the forwarding of one or more packets, an amount of processing associated with a process or thread, or any activity associated with an item.

Abstract: Presently disclosed is an apparatus and method for returning control of bandwidth allocation and packet scheduling to the routing engine in a network communications device containing an ATM interface. Virtual circuit (VC) flow control is augmented by the addition of a second flow control feedback signal from each virtual path (VP). VP flow control is used to suspend scheduling of all VCs on a given VP when traffic has accumulated on enough VCs to keep the VP busy. A new packet segmenter is employed to segment traffic while preserving the first in, first out (FIFO) order in which packet traffic was received. Embodiments of the invention may be implemented using a two-level (per-VC and per-VP) scheduling hierarchy or may use as many levels of flow control feedback-derived scheduling as may be necessitated by multilevel scheduling hierarchies.

Abstract: Schedules may use burst tolerance values to adjust the scheduling in a time-based schedule, such as, but not limited to, adjusting for accumulated but not used bandwidth, and/or adjusting eligibility of schedule entries. A best schedule item associated with an eligible schedule entry of a schedule is identified. Whether or not a particular schedule entry is eligible is typically determined based on the relationship of an associated timestamp with a current scheduling time, such as its timestamp being less than or equal to the current time. A burst tolerance time bound might also be used to allow certain priorities and/or types of items to be considered eligible if even its timestamp exceeds the current time by an amount, but less than or equal to the burst tolerance time bound.

Abstract: Rate computations are performed such as for use in scheduling activities, such as, but not limited to packets, processes, traffic flow, etc. One implementation identifies an approximated inverse rate, a fix-up adjustment value, and a quantum. An activity measurement value is maintained based on a measure of activity, and a rate control value is maintained based on the measure of activity and the approximated inverse rate. The fix-up adjustment value is applied once each quantum to the rate control value to maintain rate accuracy of the activity. In one implementation, the control value is a scheduling value used for determining when to perform a next part of the activity (e.g., send one or more packets). Scheduling rates are efficiently and compactly stored in an inverse form, which may have advantages in terms of rate granularity, accuracy, and the ability to deliver service smoothly.

Abstract: Disclosed are, inter alia, methods, apparatus, data structures, computer-readable media, and mechanisms, which may include or be used with a hierarchy of schedules with propagation of minimum guaranteed scheduling rates among scheduling layers in a hierarchical schedule. The minimum guaranteed scheduling rate for a parent schedule entry is typically based on the summation of the minimum guaranteed scheduling rates of its immediate child schedule entries. This propagation of minimum rate scheduling guarantees for a class of traffic can be dynamic (e.g., based on the active traffic for this class of traffic, active services for this class of traffic), or statically configured. One embodiment also includes multiple scheduling lanes for scheduling items, such as, but not limited to packets or indications thereof, such that different categories of traffic (e.g., propagated minimum guaranteed scheduling rate, non-propagated minimum guaranteed scheduling rate, high priority, excess rate, etc.