• Flow Specification: Token Bucket
  • Quality of service issues
    		•

    Token Bucket vs. Leaky Bucket




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    qos-f05

    Token Bucket vs. Leaky Bucket

    • Case 2: Large burst arrivals
    • 6
    • 5
    • 4
    • 3
    • 2
    • 1
    • 0
    • Arrival time at bucket
    • 6
    • 5
    • 4
    • 3
    • 2
    • 1
    • 0
    • 6
    • 5
    • 4
    • 3
    • 2
    • 1
    • 0
    • Departure time from a token bucket
    • Token bucket rate = 1 token / 2 time units
    • Token bucket size = 2 tokens

    Flow Specification: Token Bucket

    • Characterized by two parameters (r, b)
    • Assume flow arrival rate <= R bps (e.g., R link capacity)
    • A bit is transmitted only when there is an available token
    • Arrival curve – maximum amount of bits transmitted by time t
    • r bps
    • b bits
    • <= R bps
    • regulator
    • time
    • bits
    • b
    • slope R
    • slope r
    • Arrival curve

    Quality of service issues

    • Flow specification
    • Routing
      • Routing traffic to best meet demand
    • Resource reservation
    • Admission control
      • Limiting number of reservations
    • Packet scheduling
      • Packet by packet scheduling (fairness, delay)
    • RSVP addresses reservation

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