DERP relay region code (e.g. "nyc") if traffic was relayed; empty if direct.
Direct UDP endpoint used if a direct path exists (e.g. an IP:port string).
Error reason when alive is false.
Tailscale IP of the destination.
MagicDNS name of the destination peer.
Round-trip time in milliseconds. Only meaningful when alive is true.
DERP relay region code (e.g. "nyc") if traffic was relayed; empty if direct.