CIS679: Scheduling, Resource Configuration and Admission Control

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CIS679 Scheduling, Resource Configuration and
Admission Control

• Review of Last lecture
• Scheduling
• Resource configuration
• Admission control

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Review of last lecture
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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

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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

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Scheduling

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

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Priority-driven Scheduler

• 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.

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Round Robin

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

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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

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WFQ (more)

• 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.

token rate, r
arriving traffic
bucket size, b
per-flow rate, R
WFQ
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Resource Configuration

• Traffic engineering
• QoS routing
• Resource provisioning
• Network planning
• Network design

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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

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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.

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Conclusion

• Scheduling
• Decide the order of packet transmission
• Resource configuration
• Admission control