DTLS 1.2 over high-latency NB-IoT links

[humfry]

Hello,

We are using bctls-jdk18on 1.86.1 for a DTLS 1.2 server in a large NB-IoT deployment (several 100k devices).

Typical RTT is below 500ms, but for about 5-10% of devices we see RTTs up to 40 seconds.

We observe that DTLS handshake retransmissions occur well before a valid response can arrive on these high-latency links.

Before modifying BC internals, I would like to understand whether there is a supported way to configure DTLS retransmission behaviour (initial timeout, backoff strategy, retransmission count, handshake timeout).

What would be the recommended approach?

Any guidance would be appreciated.

Best regards