This is the standard recommendation for 3G throttling:
- Latency: 150ms
- Throughput: 1.6Mbps down / 750 Kbps up.
- Packet loss: none.
These exact figures are used as the WebPageTest "Mobile 3G - Fast" preset and Lighthouse's throttling default.
- The DevTools network throttling, which Lighthouse uses, is implemented within Chrome at the request-level. As a result, it has some downsides that are now summarized in this doc: Network Throttling & Chrome - status. The TLDR: while it's a decent approximation, it's not a sufficient model of a slow connection. The multipliers used in Lighthouse attempt to correct for the differences.
- Proxy-level throttling tools do not affect UDP data, so they're not recommended.
- Packet-level throttling tools are able to make the most accurate network simulation.
If you want to use more accurate throttling, read on.
This Performance Calendar article, Testing with Realistic Networking Conditions, has a good explanation of packet-level traffic shaping (which applies across TCP/UDP/ICMP) and recommendations.
The comcast
Go package appears to be the most usable Mac/Linux commandline app for managing your network connection. Important to note: it changes your entire machine's network interface. Also, comcast
requires sudo
(as all packet-level shapers do).
Windows? As of today, there is no single cross-platform tool for throttling. But there are two recommended Windows-specific network shaping utilities: WinShaper and Clumsy.
# Install with go
go get github.com/tylertreat/comcast
# Ensure your $GOPATH/bin is in your $PATH (https://github.com/golang/go/wiki/GOPATH)
# To use the recommended throttling values:
comcast --latency=150 --target-bw=1600 --dry-run
# To disable throttling
# comcast --stop
Currently, comcast
will also throttle the websocket port that Lighthouse uses to connect to Chrome. This isn't a big problem but mostly means that receiving the trace from the browser takes significantly more time. Also, comcast
doesn't support a separate uplink throughput.
# Enable system traffic throttling
comcast --latency=150 --target-bw=1600
# Run Lighthouse with it's own throttling disabled
lighthouse --disable-network-throttling # ...
# Disable the traffic throttling once you see "Retrieving trace"
comcast --stop