pub fn keepalive(transaction: TransactionId) -> Result<Vec<u8>, Error>Expand description
A keepalive on a selected pair (RFC 8445 §11, RFC 8839 §6, spec §10).
A Binding Indication with FINGERPRINT and nothing else. §11 is unusually specific: it
“MUST NOT utilize any authentication mechanism”, it SHOULD carry FINGERPRINT so the far end
can demultiplex it from media, and it SHOULD NOT carry anything more. An indication draws no
response, so this proves nothing about the path — it only holds the NAT binding open.