Constant UDP_PEER_TTL_SECS 

const UDP_PEER_TTL_SECS: u32 = _; // 300u32

How long a UDP-learned peer stays listed after its last reply. This is the staleness floor every peer gets (peer_staleness_window_secs clamps a smaller other_ttl_secs up to it), so it is the real lifetime, not a hint: ten missed probes. A departed peer therefore lingers five minutes, which is still far shorter than an mDNS peer’s TTL.