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Understanding Traffic Management and Quality of Service (QoS) in Network Performance

Traffic Management and Quality of Service (QoS) are critical in ensuring user satisfaction in network services. QoS measures how well user requirements are met by the network, influencing service performance. This includes managing specific packet flows, prioritizing traffic, and implementing scheduling mechanisms to avoid congestion. Effective traffic control strategies, such as connection admission control and usage parameter control, aim to protect the network from performance degradation while ensuring equitable resource allocation and minimal delays.

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Understanding Traffic Management and Quality of Service (QoS) in Network Performance

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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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