You Don’t Know Jack about Bandwidth

Misunderstanding performance and “just add more” scaling

• Many comments describe engineers and managers confusing latency with bandwidth/capacity.
• Pattern: when a single user is slow on an otherwise idle system, people still propose adding cores/replicas; this rarely helps and can increase cost or even worsen DB saturation.
• Analogies (e.g., multiple pregnant women for one baby) are used to illustrate non-parallelizable latency-bound work.

Latency, bufferbloat, and queue management

• Several experiences where users blame “slow bandwidth” but the real culprit is latency and bufferbloat, especially under load (downloads, saturated uplink).
• Fair-queuing + AQM (fq_codel, CAKE, LibreQoS, OpenWrt SQM) are praised for dramatically improving latency under load.
• Some note operators misinterpret “drops” from AQM as bad, when controlled dropping is essential feedback.

Application design and real-world networks

• Many anecdotes of chatty apps (old Win32 clients, web apps, database queries) that work locally but collapse over VPN/3G/satellite due to sequential round trips.
• Developers often test on low-latency, high-bandwidth office networks, missing problems that appear on 4G, rural links, or international paths.
• Frontend bloat (large third‑party scripts, tracking, banking sites loading tens of MB) is criticized as latency-insensitive design.

Home networking, tools, and router choices

• Users report good experiences replacing ISP routers with OpenWrt or OpnSense and enabling SQM; sometimes older hardware performs better due to lower latency.
• Recommended tests include Cloudflare’s speed test, Waveform’s bufferbloat test, flent, and other tools that show latency under load, not just throughput.
• Asymmetric cable (high download, low upload) is a major pain for video calls, Docker image pushes, and ML model uploads; some resort to “sneakernet”-style physical transfer.

ISPs, scaling, and economics

• There is skepticism that open-source QoS middleboxes alone will spur ISP adoption: operational complexity and organizational inertia are seen as bigger barriers than hardware cost.
• Some argue large ISPs rely on ASIC routers with huge capacity and rarely use QoS beyond access edges; others counter that smaller ISPs and regions with expensive transit still benefit.

Terminology and physics clarifications

• Disagreement over using “bandwidth” for data rate vs spectral width; some accept contextual meaning.
• Reminders that signals in fiber travel below the speed of light in vacuum and that propagation, path length, and queuing all contribute to latency.