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CS558 - Homework 8: TCP Hybla

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• Verifying TCP Hybla window increase function in the slow start phase - for a specific ρ value
  • Suppose:

    RTT = 0.1 sec RTT0 = 0.05 sec I.e., ρ = 2

    Show that the following congestion window update:

    WHi+1 = WHi + 2ρ - 1 = WHi + 3

    will result in the congestion window function

    t t ρ ----- 2 ----- RTT RTT WH(t) = ρ * 2 = 2 * 2

    NOTE:

    you only need to verify for: t = RTT, 2*RTT and 3*RTT

    In other words, verify that:

    • W^H(RTT) = 2 * 2^2*1 = 8.
    • W^H(2*RTT) = 2 * 2^2*2 = 2*16 = 32.
    • W^H(3*RTT) = 2 * 2^2*3 = 2*64 = 128.

    NOTE: During a slow start, Hybla TCP sets W^H = ρ (and not to 1) !

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• Verifying TCP Hybla window increase function in the slow start phase - general value
  • Repeat Question 1, but now use a general value for ρ

    (I.e., do not assume that ρ = 2

    Show that the following congestion window update:

    WHi+1 = WHi + 2ρ - 1

    will result in the congestion window function

    t ρ ----- RTT WH(t) = ρ * 2

    NOTE:

    you only need to verify for: t = RTT, 2*RTT and 3*RTT

    In other words, verify that:

    • W^H(RTT) = ρ * 2^ρ*1
    • W^H(2*RTT) = ρ * 2^ρ*2
    • W^H(3*RTT) = ρ * 2^ρ*3

    NOTE: During a slow start, Hybla TCP sets W^H = ρ (and not to 1) !