Anatomy of Delay

Transmission vs. propagation: where are the first and last bits? · Problem P6 (Kurose)

Link A → B, drawn to scale

Is the packet shorter or longer than the link? Make your prediction before revealing.

packet bits on the link first bit (head) last bit (tail)
t = 0 s

Keyboard: space plays or pauses · arrows step forward or back · Home / End · 1–4 jump to key moments.

Space-time diagram

packet occupying the link first bit last bit now (dashed line)

Calculator

Enter the data from any problem to check it. Accepts a decimal point or comma, and notation like 2.5×10^8 or 2.5e8. No processing or queuing delay.

dtrans = L / R
dprop = l / vp
end-to-end
packet length vp·L/R

Regime and answer hidden in prediction mode.

About this visualization

A to-scale animation of a packet sent over a link from A to B, based on problem P6 from Kurose. It shows where the first and the last bit are at every instant, next to a space-time diagram. The student adjusts packet size, transmission rate, link length and propagation speed (or picks a preset), jumps to key moments, zooms in on the head of the packet and switches on prediction mode. A calculator solves any problem statement. The main idea is that transmission delay depends on L/R and propagation delay on l/v_p, and comparing them tells whether the whole packet fits on the link at once.

Concepts: transmission delay, propagation delay, end-to-end delay, transmission rate, propagation speed, packet length on the medium, space-time diagram, break-even point.

Formulas:

Network Architecture I, Lab 1.2, problem P6 · Enrique de la Hoz, University of Alcalá · License CC BY-SA 4.0 · Source and catalogue on GitHub · DOI 10.5281/zenodo.23285664