22 a network that could route information based on this name, where this information is doesn’t matter anymore. “You give me a name, and based on that name, I decide – as the network – where the best place is to get the data for you. All of a sudden, fault tolerance is trivial, load balancing is trivial, supporting multiple regions is trivial, and as far as I can duplicate content the network supports it. The catch is that to do voice-over IP on this kind of protocol, while not impossible, is difficult because they are intended to query internet-scale data,” Corsaro adds. NDN-compatible ZettaScale has put Zenoh forward as an NDN-compatible protocol. “What we managed to do, essentially, was to come up with a protocol that puts together a publish-subscribe set of primitives that are able to run on very constrained hardware and networks, imposing minimal overhead (5 bytes), and still deliver incredible performance on a 100 GB network and blend it with NDN,” says Corsaro. Zenoh can perform diffusion and distributed query operations, and it includes a “queryable” that acts rather like an oracle in that it tells the network that anyone looking for a particular type of information should “come to me”. The queryable is integrated with third-party databases, while the routing algorithm uses the name of the data that the user is looking for and their location to work out where to go to fetch the data, he explains. “With a very simple, nimble and efficient protocol, you have data in motion. And you have what you need for data at rest – such as sensor data – so you can sort it wherever you want, and query from wherever you want, and perform computations on it. And those are the three elements you need to build a distributed system that have never been satisfied before.” While Zenoh’s first adopter was in the telecoms business, it has really started taking off in robotics, Corsaro says, and particularly in robots that run on ROS. “Why? Because the protocol they were using was DDS,” he explains. “DDS works well on fixed networks, but it doesn’t work at all well on wireless networks. The main issue is the way in which it does discovery – it completely overloads your network.” Discovery is the process by which computers and other devices on a network find each other, and it relies on set theory. “What DDS does when applications discover each other to share ‘interest’ is literally what a young kid would do to denote a set – it tells you all the elements that are in that set. What Zenoh does instead is give you a closed-form expression. All of a sudden, there is a ridiculous difference in the amount of discovery traffic – it’s reduced by 90-99%,” says Corsaro. Just come to me This reduction is because the model in Zenoh makes smarter use of set theory, exploiting intersection and generalisation, he says. “Suppose I’m a robot, and I produce information such as ‘robot one lidar’, February/March 2024 | Uncrewed Systems Technology In conversation | Angelo Corsaro ZettaScale has used a TurtleBot4 like this to demonstrate the ease of teleoperating and monitoring a robot over wi-fi with its new Zenoh bridge for ROS 2 (Image courtesy of Clearpath Robotics)
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