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A Measurement Based Admission Control Algorithm for Integrated Services Packet Networks ( extended version). S. Jamin, P. Danzig, S. Shenker, L. Zhang. Types of Services . Guaranteed service a absolute bound on delay of every packet is provided Predictive service

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A Measurement Based Admission Control Algorithm for Integrated Services Packet Networks ( extended version)

S. Jamin, P. Danzig, S. Shenker, L. Zhang


Types of services l.jpg
Types of Services Integrated Services Packet Networks ( extended version)

  • Guaranteed service

    • a absolute bound on delay of every packet is provided

  • Predictive service

    • a fair but not absolute bound on delay of every packet is provided


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Guaranteed service Integrated Services Packet Networks ( extended version)

  • Provides hard or absolute bound on delay of every packet

  • Sources are described by either peak or average rates or filter like token bucket

  • Descriptions provide upper bounds on traffic generated by source

  • Admission control algorithms use these a priori characterizations to calculate worst case behavior of flows

  • Network utilization low when flows are bursty

  • Network utilization acceptable when flows are smooth


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Predictive Service Integrated Services Packet Networks ( extended version)

  • Does not provide absolute bound on delay

  • service commitment is somewhat less reliable

  • sources characterized by token bucket filters at admission time

  • behavior of existing flows determined by measurement rather than a priori characterizations

  • when only few flows present, unpredictability of individual flows causes measurement based approach to be conservative

  • delivers significant gain in utilization only when there is high degree of statistical multiplexing


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Objective of paper Integrated Services Packet Networks ( extended version)

  • Describes a measurement based admission control algorithm for predictive service

  • To answer the following questions

    • can reliable delay bounds be provided for measurement based admission control algorithm

    • does predictive service increase network utilization


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Measurement Based Admission Control Integrated Services Packet Networks ( extended version)

  • Set of criteria controlling whether to admit a new flow

    • based on approximate model of traffic flows

    • uses measured quantities as inputs

  • Measurement process to measure the inputs

  • set of criteria used in this case

    • delay bound as a result of admitting the new flow

    • link utilization as a result of admitting the new flow


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Measurement Based Admission Control Integrated Services Packet Networks ( extended version)

  • Sources requesting services characterize worst case behavior

  • to guarantee hard bound on delay

    • worst case behavior considered

    • conservative estimate of bound obtained

    • new flow may not be admitted due to conservative estimate

    • results in low utilization

  • to achieve fairly reliable bound for predictive service

    • approximate maximal delay by replacing worst case parameters with measured quantities

    • results in higher utilization


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Worst case delay Integrated Services Packet Networks ( extended version)

  • Theorem by Parekh says the delay bound for a class j is the one time delay burst that accrues if the aggregate bucket of all classes 1 through j flows are simultaneously dumped into the switch and all classes 1 through j-1 sources continue to send at their reserved rates with j having lowest priority

  • this worst case delay can change

    • when flow of same class is admitted

    • when flow of higher priority class is admitted

    • when guaranteed flow is admitted

  • classes classified according to the delay bounds tolerated by that class


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Computation of new delay bound Integrated Services Packet Networks ( extended version)

  • The delay bounds as a result of admitting the new flow is computed

  • for e.g.,

  • When new predictive flow a of same class is admitted

    • new delay bound = old delay bound + k( bucket size of a)

  • similarly new delay bounds are calculated for the case

    • When new predictive flow a of lower class is admitted

    • When new guaranteed flow a is admitted


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Equivalent Token bucket filter Integrated Services Packet Networks ( extended version)

  • In equations replace worst case values by measured values

    • substitute the reserved rates by the measured rates

    • substitute the worst case delays by the measured delays

  • this results in describing the existing aggregate traffic by an equivalent token bucket filter with parameters determined from traffic measurement


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Admission control algorithm Integrated Services Packet Networks ( extended version)

  • New predictive flow: if incoming flow a requests predictive service in a particular class

    • request denied if sum of flow’s requested rate and current usage exceeds link utilization level

    • request denied if admitting new flow violates delay bound of the same priority level

    • request denied if admitting new flow violates delay bound of the lower priority level


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Admission control algorithm Integrated Services Packet Networks ( extended version)

  • New guaranteed flow: if incoming flow a requests guaranteed service

    • request denied if total bandwidth of the flows including new flow exceeds link utilization level

    • request denied if admitting new guaranteed flow violates delay bound of predictive services

    • this is due to the decrease in the bandwidth available for predictive flows due to admission of a guaranteed flow


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Measurement mechanism: Time window Integrated Services Packet Networks ( extended version)

  • Two measurements

    • experienced delay

    • utilization

  • to estimate delays measure the queuing delays d of every packet

  • to estimate utilization sample the usage rate of the guaranteed service and the predictive class over sampling period of S packet transmission units


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Measuring delay Integrated Services Packet Networks ( extended version)

  • Measurement variable to estimate queuing delay is D

  • Measurement window of T packet transmission units used as basic measurement block

  • value of D updated on three occasions

    • at end of measurement block D updated to reflect maximal packet delay seen in previous block

    • when individual delay measurement exceeds estimated maximum queuing delay D is updated to times the sampled delay

    • whenever a new flow is admitted D is updated to the value of projected delay from equation


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Measuring rate Integrated Services Packet Networks ( extended version)

  • Measurement variable to estimate queuing delay is V

  • Measurement window of T packet transmission units used as basic measurement block

  • value of V updated on three occasions

    • at end of measurement block V updated to reflect maximal sampled utilization seen in previous block

    • when individual utilization measurement exceeds estimated V, V is updated to the sampled value

    • whenever a new flow is admitted V is updated


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Performance Tuning Integrated Services Packet Networks ( extended version)

  • Parameters , S, T can be varied for better performance

  • smaller S, more sensitive to bursts , larger S smoother traffic

  • smaller T means more adaptability to changes in traffic load, larger T results in more stability

  • larger T results in fewer delay violations and lower link utilization


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COPS Integrated Services Packet Networks ( extended version)

  • A simple client/server model for supporting policy control over QoS signaling protocols and provisioned QoS resource management

  • used to exchange policy information between a policy server (PDP) and its clients (PEP)

  • for e.g., a policy client maybe RSVP routers that must exercise policy based admission control over RSVP usage


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COPS Integrated Services Packet Networks ( extended version)

  • A simple client/server model for supporting policy control over QoS signaling protocols and provisioned QoS resource management

  • used to exchange policy information between a policy server (PDP) and its clients (PEP)

  • for e.g., a policy client maybe RSVP routers that must exercise policy based admission control over RSVP usage