Using https with NB-IoT, instead of COAP,DTLS

[lseg]

Hi,

I am a bit confused, I understand from some technical discussions that we should use COAP/UDP (with DTLS) instead of HTTP/TCP (with TLS) when using NB-IoT.

For LTE-M  HTTP/TCP should work properly. 

I am mainly concerned about FOTA where we download files up to 2Mb. I see that even with LTE-M the connection is sometimes lost and it reconnects without any issue.

Now what is my confusion: we actually never used COAP before and we have devices which are perfectly doing a FOTA over NB-IoT using HTTPS. So what exactly is the reason to use COAP instead of HTTPS. In which cases will the HTTPS download over NB-IoT fail? And in which cases is COAP really needed?

We only have very few devices connected over NB-IoT, so if I want to do this effort I want to know first if it is really needed. And on the other hand if I send devices to countries with only NB-IoT (e.g. Greece): will it give issues if I use HTTPS for FOTA download.

Kind regards,

Luc Segers

[Didrik Rokhaug]

Hi,

As Achim said, in most cases, HTTP and TCP works fine over NB-IoT.

However, depending on the network, signal conditions and server, the latency might become too big in some cases.

As UDP is more flexible when it comes to handling latency (the latency and acknowledgements are handled at the application level rather than the transportation level), it can be better suited in situations with high latency.

If the device is moving, and can be expected to move out of bad coverage situations, and/or you can do tests before deploying to new networks and locations, you will probably be fine with just TCP.

If not, you might want to consider having some back-up options.

Though if the device is mobile and battery driven, I would also consider just postponing the FOTA upgrade, as sending and receiving data with bad coverage consumes more power than in good coverage.

Best regards,

Didrik