• Route Pinning
  • How Is the Token Bucket Used
  • QoS Guarantees: Per-hop Reservation
  • Cs 552 Computer Networks Quality Of Service




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    RSVP RESV MESSAGE

    • From receiver to sender(s) to reserve resources
    • Sent hop-by-hop using PHOP information
    • Reservation style and flow description
      • Reservation style (FF,SE, WF)
      • Fixed-filter, Shared-explicit, wildcard-filter
      • Senders to which the reservation applies
      • Rspec, QoS specific requirements
      • RSpec is highly specific to the service required, and may include information like bandwidth allocation, maximum delay, or packet loss probabilities etc.
    • RESV messages processing at each hop

    Route Pinning

    • Problem: asymmetric routes
      • You may reserve resources on RS3S5S4S1S, but data travels on SS1S2S3R !
    • Solution: use PATH to remember direct path from S to R, i.e., perform route pinning
    • S1
    • S2
    • S3
    • S
    • R
    • S5
    • S4
    • PATH
    • RESV
    • IP routing

    How Is the Token Bucket Used?

    • Can be enforced by
      • End-hosts (e.g., cable modems)
      • Routers (e.g., ingress routers in a Diffserv domain)
    • Can be used to characterize the traffic sent by an end-host

    Source Traffic Characterization

    • Arrival curve – maximum amount of bits transmitted during an interval of time Δt
    • Use token bucket to bound the arrival curve
    • Δt
    • bits
    • Arrival curve
    • time
    • bps

    QoS Guarantees: Per-hop Reservation

    • End-host: specify
      • the arrival rate characterized by token-bucket with parameters (b,r,R)
      • the maximum maximum admissible delay D
    • Router: allocate bandwidth ra and buffer space Ba such that
    • bits
    • b*R/(R-r)
    • slope r
    • Arrival curve
    • D
    • Ba
    • slope ra

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    Cs 552 Computer Networks Quality Of Service

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