75 lines
3.7 KiB
Markdown
75 lines
3.7 KiB
Markdown
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# Wi-Fi/projector/dashboard diagnostics notes
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Use this reference for recurring home-network investigations where the user wants an understandable history dashboard plus occasional packet evidence. The class of task is: Wi-Fi/SSH/tmux lag with changing topology, phone hotspots, projectors/streaming devices, and non-technical viewers.
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## Storage and legibility defaults
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- Do not write repeated diagnostics to the Desktop.
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- Use a single run directory under `~/.local/state/hermes/net-tests/<scenario>-<timestamp>/`.
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- Put generated dashboards under `~/.local/share/hermes/net-dashboard/`.
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- For non-technical viewers, lead with spike charts and plain-language event cards. Keep tables and packet details behind `<details>`.
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## Event markers matter
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When the user reports a real-world change, immediately write a marker file in the active run directory with:
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- machine timestamp (`date --iso-8601=seconds`)
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- user-observed timestamp if different (e.g. installer top-bar time)
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- exact text/status the user saw
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- current quick pings if useful
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Examples of useful markers:
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- projector turned on / streaming started
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- Ubuntu installer visible / finished
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- APT transaction summary visible
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- Bluetooth turned off
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- phone hotspot/network switch
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If a capture window ended before the user's marker, say so clearly: that run is a pre-event baseline, not post-event evidence.
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## Avoid false single-cause stories
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Projector tests can have multiple simultaneous variables. Label the dashboard accordingly rather than saying "Epson only" when other load is active.
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Example topology note to capture:
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- debby is on phone hotspot in basement
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- projector/router are upstairs
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- another Ubuntu laptop is also on the hotspot near the projector/router
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- Ubuntu installer may or may not still be downloading
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- Android hotspot client isolation may prevent seeing the other laptop in `ip neigh`
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Interpret spikes by segment:
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- clean gateway + spiky internet/Tailscale => upstream/mobile/hotspot saturation or bufferbloat
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- spiky gateway too => local Wi-Fi/RF/hotspot contention
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- improvement after Ubuntu install finishes => installer/download load was relevant
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- continued spikes after installer finishes while projector streams => projector/streaming or broader RF/mobile path remains suspect
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## Short pcap sampling pattern
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With low disk space, avoid continuous pcaps. Prefer periodic short packet samples:
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- 20 seconds every 5 minutes
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- strict per-sample filesize caps
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- stop below a free-space threshold
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- capture control/diagnostic traffic and interactive paths, not full large-download payloads
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Suggested filters:
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- Wi-Fi interface: `arp or icmp or port 53 or udp port 5353 or udp port 5355 or udp port 1900 or udp port 3702 or udp port 41641 or host <gateway> or net <hotspot-subnet>`
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- Tailscale interface: `tcp port 22 or icmp`
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Keep pcaps under the active run directory in `pcap-samples/`, and summarize them into the dashboard later. Do not dump raw packet logs into chat.
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A reusable sampler script is available at `scripts/periodic-pcap-sampler.sh`.
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## Bluetooth on 2.4 GHz
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If Wi-Fi is also 2.4 GHz, Bluetooth can sometimes contribute to local jitter because Wi-Fi/Bluetooth coexist on nearby spectrum and often shared hardware. Treat Bluetooth-off as a marker and compare before/after; do not overclaim. If local gateway ping stays good but internet/Tailscale remains hundreds of ms, Bluetooth is not the main cause.
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## Ubuntu installer / APT evidence
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Installer screenshots can provide useful network-load timing. Record visible logs with both report time and screenshot/log timestamps. For example, an APT summary showing `Need to get: 218 MB` and visible `Get:` lines around 23:49 means a real download phase occurred then, even if the user reports it later.
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