CN Boon Han

CN Boon Han

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I love to learn and build! Currently interested in Embodied AI 🤖, Languages 🗣️ and Hiking ⛰️

Speeding Up Downloads using Multiple WANs on Raspberry Pi

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We may often find ourselves in situations needing to download large files. However, our download link may not always have enough bandwidth, or we could be rate-limited by the WAN provider. Wireless@SGx, for example, is widely used but has a limit of 5Mbps (although practically it could reach 30Mbps). How could we improve this?

Idea

Large downloads are often the result of having to download multiple files in aggregate. For example, a model checkpoint download often contains multiple .safetensor files. If we have multiple authenticated WANs on a router, we should be able to load balance the individual downloads among these WANs and utilize a larger overall bandwidth.

Requirements

In this example, I am utilizing two WANs links. One link will use the onboard Wifi chipset. Another link will use USB tethering from a phone. Modify accordingly if you increase number of WANs / use Ethernet etc.

If you intend to use USB Wifi Adapter, do take note of firmware compatibility.

  1. Raspberry Pi ( I use RPi 5 )
  2. OpenWRT Factory Image for Raspberry Pi
  3. SD Card
  4. Developer Laptop
  5. Ethernet Cable
  6. Mobile Phone & Cable for USB tethering

Setup

  1. Follow the instructions to flash an SD card with the OpenWRT Factory Image.
  2. Use Ethernet Cable to connect your Laptop to the Raspberry Pi.
  3. Access Router Configuration Page at 192.168.1.1 through a browser.
  4. Access the wireless page and authenticate to a Wifi hotspot. Your OpenWRT router should now have access to Internet.
  5. Access Router over ssh root@192.168.1.1
  6. opkg update && opkg install kmod-usb-net-rndis kmod-usb-net-cdc-ether usbutils luci-app-mwan3
  7. On the Admin page, add a new DHCP client with the usb0 interface. Assign it to wwan firewall zone. Ensure that a gateway metric is set for the usb0 and wwan interfaces. Set slightly different values for each (usb0 to 20, wwan to 10, for example.) Create USB Interface OpenWRT Firewall Zone for USB Interface alt text
  8. Configure the MultiWAN Manager under cgi-bin/luci/admin/network/mwan3 with the following: alt text alt text alt text alt text alt text alt text
  9. Run on SSH terminal: mwan3 status. Verify that both WANs are online, and the load balancing ratio is 50/50. alt text
  10. Run on SSH terminal multiple times: wget -qO- https://ipecho.net/plain ; echo alt text

In theory, this arrangement should allow you to load balance multiple download HTTP requests across your WANs. An additional benefit is the automatic failover that triggers on link failure.