This is a quick guide on how networking works in FRC. This will talk about the interaction between the Driver Station laptop, the FRC radios, and the robot and its components.
Because of its proximity, all of the networking on the robot is done via wired ethernet. The main components that use networking are the Limelights and the RoboRIO. To connect multiple Limelights, the RoboRIO together, and the AP (discussed later), we use a network switch. The Limelights are assigned static IPs such as 10.0.0.10 or 10.0.0.11. To connect the robot to the rest of the field or to the driver station, it needs to be connected wirelessly because it's obviously impractical to hard wire a moving robot on a field. For this, the robot has a VH-109 Access Point.
More information can be found on the Vivid Hosting website, but here's a quick rundown. The simplest (and worst) way to connect the Driver Station to the laptop is by having the robot radio broadcast an SSID that the Driver Station will connect to. However, the robot radio can only broadcast a 2.4Ghz network which will have more interference in school settings and has less throughput than a 6 GHz radio.
The next upgrade is to use two radios. One is a dedicated access point and is usually right next to the Driver Station laptop. The robot radio will be configured to connect to the access point as a client instead of broadcasting its own SSID. The benefit to this is that the access point can broadcast a 5 GHz network which has less interference and more throughput than a 2.4GHz network. Additionally, since the AP is right next to the laptop, the laptop can be directly connected to the AP via an RJ45 cable instead of connecting over Wi-Fi. The only downside to this setup is that it requires two radios, and this becomes harder and harder with managing multiple robots during build season.
The in depth review of the competition field network can be found here, but this will be a quick summary of the field network and how we are attempting to apply it to our home field. VLANs are a generic networking concept that basically separates networks that are traveling through the same physical wire. On the field, it is a terrible idea to run 6 networks, one for every team on the field. Instead, the better solution is to use VLANs to logically separate the traffic of the 6 teams while routing them through the same access point and wires. By putting the teams on different VLAN IDs, the teams can use the same physical wires to transmit data without interfering with each other's traffic. The competition field network is a little more complex, but this is the basic structure that we are planning on moving to our home field. The benefit to this type of networking is that we get the benefit of 5 GHz networks, less interference from two robot's individual networks, and optimize our usage of physical radios. In this setup, we have one big field radio and every team only needs their robot radio.