Traffic Management & QoS

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

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

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

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

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

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

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)

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

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

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

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

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

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

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

Traffic Parameters: Requirements 4 Simple and understandable 4 Useful for traffic control and congestion control 4 Measurable and controllable

Traffic Parameters JATM Traffic Descriptor 3 source traffic descriptor 3connection traffic descriptor

Traffic Parameters Source Traffic Descriptors Connection Traffic Descriptors

Traffic Parameters ATM Traffic Contract and Negotiation 3 connection traffic descriptor 3 requested QoS class 3 the network’s definition of a compliant connection

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)

Traffic Control & Congestion Control Traditional Flow Control Mechanisms such as window or feedback based mechanisms are: (unsuitable) 3Inertia of flows 3Large bandwidth propagation delay product

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

Traffic Control & Congestion Control Traffic source Congestion

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

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

Usage Parameter Control Supervise existing calls to ensure: 3network users abide by their traffic contracts 3ensure that excessive traffic as a result of unintentional or malicious behavior will not result in a performance degradation of other network users

Usage Parameter Control: Requirements 3capability of detecting any non-compliant traffic 3rapid response to parameter violations 3selectivity over the range of checked parameters 3non-interference with non-excessive traffic 3no significant delay to the traffic 3simplicity

Usage Parameter Control (UPC) or “Policing”

GCRA(T,  )