This note was meant to cover how network performance is measured and never got past the first definition. The two headline metrics are bandwidth (or throughput), the number of bits per second a link or path can move, and latency (or delay), the time a message takes to cross it.
Bandwidth vs. latency
Bandwidth is how wide the pipe is, latency is how long it is, and the two are independent. A satellite link can be high-bandwidth and high-latency at once, and a short serial cable low-bandwidth and low-latency. More parallelism (more channels, wider signals) buys bandwidth, but only a shorter path or a faster medium cuts propagation latency.
Until this gets written, the physical layer works a latency example with the transmission and propagation delay formulas, coding and modulation covers the bandwidth-delay product, and information theory covers the hard limits on link capacity.