# ARQ windows and utilization

Subject: Computer Networks

Exam: TEE

Reader: https://deep-learning-study-room.vercel.app/cn/#tee/practice/tee-formulas/arq

Canonical: https://deep-learning-study-room.vercel.app/read/cn/tee/practice/tee-formulas--arq/

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



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



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



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



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



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



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



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



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



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



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

[Utilization worked examples](https://deep-learning-study-room.vercel.app/read/cn/tee/practice/arq--efficiency-1/)