Offline networking

Introduction

Offline and off-grid networking broadly refers to the practice of sharing information between devices without use of the global Internet. The advantage of this in a disaster scenario is to provide a fallback for access to critical information and communication services in cases where reaching the Internet is not possible. This can be done with a device acting as a WiFi access point and router, LoRaWAN devices sharing information over long distances using the LoRa radio specification, or with a digital radio service known as packet radio. Each of these will be covered here.

WiFi

WiFi (or Wi-Fi) refers to a collection of wireless protocols from the 802.11 collection of standards. WiFi is predominantly used for low power, short range networking, and centers around 2 popular bands, 2.4GHz and the faster 5GHz. In 2019, it was found more than 3.05 billion Wi-Fi-enabled devices are shipped globally each year. Each of these devices can connect to any wireless access point which is open, or for which they are authenticated. This presents a significant opportunity for the distribution of critical information where Internet access is otherwise not available.

Offline WiFi access points

Due to our habitual relationship with WiFi and connecting to the public Internet, we can often overlook WiFi's applications in 'offline' contexts. A a WiFi access point (AP) does not need the public Internet to provide access to content, if the content is locally accessible to the AP. In such applications, either the WiFi router itself holds the data (perhaps on a USB stick), or the data is served from another device connected directly to the AP.

OpenWrt

Some commercial routers provide ability for file sharing across their network using the factory firmware installed on the device. However in the majority of applications, an after market firmware is used, like OpenWrt. OpenWrt is an open source project and community dedicated to writing and testing firmware that can be 'flashed' onto scavenged or bought WiFi routers, providing them with new functionality and customisation options. At the time of writing, 2043 wireless access points are supported by OpenWrt to some degree.

Many projects have been done exploring the practical application of offline networking in a wireless context using OpenWrt. However, many small form-factor computers can be repurposed as WiFi access points, that either route through to another network (like the Internet) or remain hermetic.

For those more technically inclined, any GNU/Linux laptop or device with a wireless network adapter can be repurposed as a wireless access point serving information and files from a locally hosted website. A popular webserver for use in such contexts is lighttpd. A popular daemon/service providing access point functionality is hostapd, often coupled with dnsmasq to provide automatic network configuration of clients using the DHCP protocol alongside domain name resolution.

WiFi mesh networks

Image showing connections between nodes of the Freifunk network in Berlin in 2007.

Mesh networks are computer networks that have in-built node redundancy, meaning that no central node is critical to the distribution of information across the network. Routing algorithms ensure that if a node is unavailable along the route, another optimised route is chosen. Mesh networks are in wide use throughout military and disaster response applications, but can also be deployed and managed by civilians with low cost equipment.

A low power mesh network run by a community atop dumpster-dived/recycled or bought wireless routers could provide a valuable means of distributing mission-critical information where cellular infrastructure or the public Internet is otherwise unavailable.

Freifunk

Among the most well known and successful WiFi mesh networks in the world is Freifunk. Established in 2003 in Germany, one of the primary goals of the project is to build a large-scale free wireless Wi-Fi network that is decentralized, free of discrimination (net neutrality), owned by those who run it, and to support local communication independent of the public Internet. Comprising over 41,000 wireless access points run by civilians, the Freifunk firmware is based atop OpenWrt and runs the batman-adv (B.A.T.M.A.N) mesh networking protocol, which is actively developed by Freifunk activists.

The Freifunk firmware can be freely downloaded and modified to be deployed anywhere(DE).

Red Hook WiFi

Red Hook Wifi was established in Red Hook, Brooklyn, New York City in 2011. It was created by the Red Hook Initiative to provide access to broadband for the regions many residents. A survey found that many people in the area accessed the internet primarily through mobile phones and that over 30% of the population did not have broadband access at home. .

Red Hook serves as an excellent example of community-run infrastructure serving a critically important role in an environmental emergency. In 2012, when Hurricane Sandy hit the region, Internet and cellular communications systems were down. During this crisis the Red Hook mesh network not only remained active, but the Red Hook headquarters became a hub for volunteer coordination and food distribution, and residents came to the Red Hook Initiative's office to charge their devices and connect to the internet.

Soon after Hurricane Sandy hit, the Federal Emergency Management Agency of the United States connected itself to the Red Hook Network, providing a satellite uplink, connecting itself, the Red Cross and residents such that they could find out about food banks, shelters and emergency information.

Other mesh networks by region

Wikipedia hosts a page dedicated to listing mesh networks by region.

Linkdump

(to be expanded out into text)

http://subnodes.org/

https://learn.adafruit.com/lora-and-lorawan-radio-for-raspberry-pi/overview

https://en.wikipedia.org/wiki/Packet_radio

https://meshtastic.org/

https://en.wikipedia.org/wiki/Freifunk

https://openwrt.org