Question

Ignoring switching delay determine the maximum possible data throughput when HDLC is used to transmit 1024 bit frames with 3 bit sequence numbers and a 16 bit FCS across a 1Mbps data rate link with a propagation delay of 270ms?

Answer 1

Data Rate is 1 mbps = 10^6

FCS Size = 16 bits

Payload size = Frame size - FCS size ==> 1024 - 16 ==> 1008

Tframe = Frame size/ Data rate ==>1008/10^6 => 1.008 * 10^(-3)

Tpropagation = 270 * 10^(-3)

a = Tpropagation/Tframe ==> 270 * 10^(-3) / 1.008 * 10^(-3) => 267.857

Window size(W) = (2^n+1) ==> 7 (3 bit sequence)

Max. Thoughput(U) = W / 2a + 1

U = 7 / (2*267.857 + 1) => 0.01304(approx)

So maximum data Thoughtput is 0.01304

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