# A network has a data transmission bandwidth of 20 × 106 bits per second. It uses CSMA/CD in the MAC layer. The maximum signal propagation time from on

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A network has a data transmission bandwidth of 20 × 106 bits per second. It uses CSMA/CD in the MAC layer. The maximum signal propagation time from one node to another node is 40 microseconds. The minimum size of a frame in the network is ______bytes.

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Data:

L = size of frame

BW → bandwidth = 20 × 106 b/s

Tp → propagation time = 40 μs = 40 × 10-6 s

Tt → transmission time

Formula:

For CSMA/CD,

Tt ≥ 2 × Tp

${{\rm{T}}_{\rm{t}}} = \frac{{\rm{L}}}{{{\rm{BW}}}}$

Calculation:

$\frac{{\rm{L}}}{{{\rm{BW}}}} \ge 2 \times 40 \times {10^{ - 6}}$

L ≥ 2 × 40 × 10-6 × 20 × 106

L ≥ 1600 bits

L ≥ 200 bytes

Lmin = 200 bytes

Therefore, the minimum size of a frame in the network is 200 bytes.