DTLS 1.2 retransmission timeouts

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1

By accident I found, that golioth uses a fixed retransmission timeout of 1s.

(I tried to upload a WireShark capture, but that seem not to work ;-).

The recommendation in RFC6347 is a backoff of 2, means on reach retransmission the timeout is doubled (see RFC6347 4.2.4.1. Especially with “narrow band” communication, the overall performance gets better with such a backoff strategy. E.g. with cellular NB-ioT the RTT is something about 2-3s and using fixed 1s retransmission results in a frequently useless retransmissions.

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What is the SDK you used during testing and Wireshark capture?
GitHub - golioth/golioth-zephyr-sdk: Golioth SDK For Zephyr or GitHub - golioth/golioth-firmware-sdk: Firmware SDK enabling any IoT device to connect to Golioth - the Universal Connector for IoT?

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I’m pretty sure, that the server side retransmission timeout is not related to the SDK.
I used Cf-Browser from Eclipse/Californium in order prepare to adapt my zephyr-coaps-client to support golioth.

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Thanks for the report @achim.kraus! We are aware of this issue at the server and are working on addressing it ASAP.