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CIS679: Scheduling, Resource Configuration and Admission Control

CIS679: Scheduling, Resource Configuration and Admission Control. Review of Last lecture Scheduling Resource configuration Admission control. Review of last lecture. Scheduling Mechanisms.

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CIS679: Scheduling, Resource Configuration and Admission Control

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  1. CIS679: Scheduling, Resource Configuration and Admission Control • Review of Last lecture • Scheduling • Resource configuration • Admission control

  2. Review of last lecture

  3. Scheduling Mechanisms • Scheduling: choosing the next packet for transmission on a link can be done following a number of policies; • FIFO: in order of arrival to the queue; packets that arrive to a full buffer are either discarded, or a discard policy is used to determine which packet to discard among the arrival and those already queued

  4. Scheduling Policies • Priority Queuing: classes have different priorities; class may depend on explicit marking or other header info, eg IP source or destination, TCP Port numbers, etc. • Transmit a packet from the highest priority class with a non-empty queue • Preemptive and non-preemptive versions

  5. Scheduling • Scheduling: • FIFO • Priority Scheduling (static priority) • Round Robin • Weight Fair Queuing (WFQ)

  6. packets are transmitted according to their priorities; within the same priority, packets are served in FIFO order. Complex in terms of no provable bounded delay due to no flow isolation Simple in terms of no per-flow management: SP make it possible to decouple QoS control from the core-router. D = ?? max Priority-driven Scheduler

  7. Round Robin • Round Robin: scan class queues serving one from each class that has a non-empty queue

  8. WFQ • Weighted Fair Queuing: is a generalized Round Robin in which an attempt is made to provide a class with a differentiated amount of service over a given period of time

  9. Worst case traffic arrival: leaky-bucket-policed source Complex in terms of having per-flow isolation mechanism, hence needing per-flow state maintenance and resource reservation at per-element: WFQ couple QoS control to the core-router. Simple in terms of having mathematically provable bound on delay, which makes admission control simple. D = b/R max WFQ (more) token rate, r arriving traffic bucket size, b per-flow rate, R WFQ

  10. Resource Configuration • Traffic engineering • QoS routing • Resource provisioning • Network planning • Network design

  11. Admission Control • Session must first declare its QOS requirement and characterize the traffic it will send through the network • R-spec: defines the QOS being requested • T-spec: defines the traffic characteristics • A signaling protocol is needed to carry the R-spec and T-spec to the routers where reservation is required; RSVP is a leading candidate for such signaling protocol

  12. Admission Control • Call Admission: routers will admit calls based on their R-spec and T-spec and base on the current resource allocated at the routers to other calls.

  13. Conclusion • Scheduling: • Decide the order of packet transmission • Resource configuration • Admission control

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