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Traffic Management & QoS

Traffic Management & QoS. Quality of Service (QoS). The collective effect of service performances which determine the degree of satisfaction of a user of the specified service. Quality of Service (QoS).

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Traffic Management & QoS

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  1. Traffic Management & QoS

  2. Quality of Service (QoS) • The collective effect of service performances which determine the degree of satisfaction of a user of the specified service.

  3. Quality of Service (QoS) • The collective effect of service performances which determine the degree of satisfaction of a user of the specified service. • Is a measure of the extent to which the user’s requirement are sustained by the network.

  4. Traffic Management & QoS • is concerned with the delivery of QoS to specific packet flows • mechanisms for managing the flows in a network • setting of priority and scheduling mechanisms

  5. Generic Functions • Network resource management (NRM) • Connection Admission Control (CAC) Usage • Usage/ Network Parameter Control • Priority control • Traffic shaping • Feedback controls

  6. Traffic Control & Congestion Control Aim: Protect the network and end system from becoming congested

  7. Traffic Control & Congestion Control Congestion: State of network elements in which the network is unable to meet the negotiated network performance objectives. Usually due to: • Unpredicatable traffic flow fluctuations • Faults

  8. Traffic Control & Congestion Control Traffic Contract: Agreement between the customer and the network provider at call-set up. Forms the basis of the ATM connection Resource allocation to guarantee the negotiated Quality of Service (QoS)

  9. Major Issues & Scheduling Mechanisms End-to-end delay: sum of delays experienced at each multiplexer Jitter: variability in the end packet delays Packet Loss:

  10. FIFO and Priority Queues FIFO first in first out queueing FIFO queueing with discard priority HOL Head of Line priority queueing

  11. Problems: Does not provide some degree of guaranteed access to transmission bandwidth to the lower priority classes Does not discriminate between users of the same priority

  12. Priority Tags: Method of defining priority tags is open and could be dynamic priority class + arrival time due date

  13. Fair Queueing: Prevents hogging transmission bandwidth is divided equally amongst all non-empty queues

  14. Weighted Fair Queueing: Each flow has its own queue but each user also has a weight that determines its relative share of the bandwidth

  15. Traffic Parameters Is a specification of a particular traffic aspect quantitative: mean holding time, the peak cell rate, average burst length qualitative: source type ~ telephone, video phone

  16. Traffic Parameters: Requirements • Simple and understandable • Useful for traffic control and congestion control • Measurable and controllable

  17. Traffic Parameters • ATM Traffic Descriptor • source traffic descriptor • connection traffic descriptor

  18. Traffic Parameters SourceTraffic Descriptors ConnectionTraffic Descriptors

  19. Traffic Parameters ATM Traffic Contract and Negotiation • connection traffic descriptor • requested QoS class • the network’s definition of a compliant connection

  20. Traffic Control & Congestion Control Traffic Control: set of actions to avoid congestive (Preventive) Congestion Control: set of actions to minimize the intensity spread and duration of congestion (Reactive / Feedback)

  21. Traffic Control & Congestion Control Traditional Flow Control Mechanisms such as window or feedback based mechanisms are: (unsuitable) • Inertia of flows • Large bandwidth propagation delay product

  22. Traffic Control & Congestion Control The greater the bandwidth the greater the cells in transit

  23. Traffic Control & Congestion Control Congestion Trafficsource

  24. Traffic Control & Congestion Control Reactive techniques  Preventive strategies:  Throttle the traffic at the source S Traffic Source Traffic Control

  25. Connection Admission Control Calculate Effective bandwidth based on connection / traffic descriptors and decide how much bandwidth to reserve for the source

  26. Usage Parameter Control Supervise existing calls to ensure: • network users abide by their traffic contracts • ensure that excessive traffic as a result of unintentional or malicious behavior will not result in a performance degradation of other network users

  27. Usage Parameter Control: Requirements • capability of detecting any non-compliant traffic • rapid response to parameter violations • selectivity over the range of checked parameters • non-interference with non-excessive traffic • no significant delay to the traffic • simplicity

  28. Usage Parameter Control (UPC) or “Policing”

  29. GCRA(T, )

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