Networking

In Celestial, all machines are equipped with a virtual network adapter that is available within the microVM as eth0. Each machine is placed in a dedicated subnet. Machines that can communicate with each other (these are machines where a network path exists between their corresponding satellites or ground stations) can find each other using the DNS service described below.

All networks are subnets of the 10.0.0.0/8 network. Networks are calculated as follows:

1. Byte is always 10 (0x0A)
2. Byte is the shell identifier, 0 for ground stations and starting at 1 for satellite shells
3. Byte is the satellite’s identifier in the shell, shifted right by 6 bits (e.g. 12 or 0x0C for satellite 831)
4. Byte is the satellite’s identifier in the shell, shifted left by 2 bits (e.g. 252 or 0xFC for satellite 831)

Within this network, the network + 1 is the gateway IP and network + 2 is the microVMs IP. The network has a /30 network mask, hence only those two are available.

eBPF programs and tc are used to modify network latency between microVMs. WireGuard is used to link machines on different hosts.