In September [of 2013], a Marketplace.org story about the NSA revelations included the quote “one suggested solution for users trying to avoid surveillance is to operate on an entirely separate network. A so-called mesh network is made of phones and other devices that talk to each other without the help of an Internet service provider.” What is a mesh network, and would it really help avoid surveillance?
In comparison to the more familiar networks, which distinguish between “devices” and network components like routers, nodes in a mesh network perform both functions, originating their own traffic as well as forwarding traffic from other nodes. These networks are also often “ad-hoc”, meaning that the ways in which traffic is routed cannot count on a well-established topology or connections between specific nodes. Much of the early development was conducted by the military, which wanted to quickly spread a bunch of sensors around an area, have the sensors work together to communicate any findings of interest, and have the ability for a soldier entering the sensor field to be able to get readings directly from any sensor. A second example is in the developing arena of self-driving cars, where a car on the road would like to connect directly to other cars in the area to exchange information, even though the set of cars in range varies continuously. These types of use cases drive a third typical characteristic of mesh networks, low power consumption.
Because of the differences in how these networks are used, they also operate a bit differently. One interesting approach is “flooding”, where a sensor just broadcasts a packet when it sees something interesting, and any other sensor in range will then re-broadcast it in turn. Each sensor remembers packets it has seen recently so the network is not “self-spamming”. Eventually some node might be an interested human, or have a connection to the internet for forwarding of the information. These networks are very flexible, and very fault tolerant since any possible path in the network will be used even if many nodes have failed or are unavailable.
Some other interesting use cases for these kinds of networks include emergency response (see article on mesh network use after Hurricane Sandy), the Internet of Things (billions of low power sensors), and manufacturing processes using protocols such as those developed by The ZigBee Alliance. In all of these cases, because the networks operate in their own autonomous little world, the claim of the Marketplace story that they are “an entirely separate network…without the help of an internet service provider” is generally true. And as mentioned yesterday, the use of mesh networks for independent communication among individuals, especially in restrictive environments seems to be a growing phenomenon.