Computer Networks · TEE · practice

ARQ windows and utilization

Extra mathematical models

TEE · Complete six-unit quick reference · current syllabus 702AI0C023

N=2^m,\quad W_{GBN}\le N-1,\quad W_{R,GBN}=1LaTeX: N=2^m,\quad W_{GBN}\le N-1,\quad W_{R,GBN}=1

m sequence bits; sequence numbers 0…N−1. GBN receiver accepts only next in order.

W_{S,SR}=W_{R,SR}\le N/2LaTeX: W_{S,SR}=W_{R,SR}\le N/2

Standard equal-window SR bound; prevent successive windows overlapping.

U_{SW}=\frac{T_t}{T_t+2T_p+T_a}LaTeX: U_{SW}=\frac{T_t}{T_t+2T_p+T_a}

Ideal error-free Stop-and-Wait; Tt data transmission, Tp one-way propagation, Ta ACK transmission.

U_W=\min(1,WT_t/(T_t+2T_p+T_a))LaTeX: U_W=\min(1,WT_t/(T_t+2T_p+T_a))

Supporting ideal pipeline bound; no queueing/processing, equal frames.

W_{need}=\lceil(T_t+2T_p+T_a)/T_t\rceilLaTeX: W_{need}=\lceil(T_t+2T_p+T_a)/T_t\rceil

Round upward for a full pipeline, then verify numbering constraints.

Utilization worked examples