Re: [iot-wg] CoAP and CGN

[Julien Vermillard <jvermillard@xxxxxxxxx>]

Sorry, I probably miss phrased "usual TLS/TCP".

Yes TLS PSK is also quite compact, but mosquitto is the only broker I know which support it.

(ex: hivemq or aws iot doesn't support it). So in my view it's not "usual".

For example it's not working for Paho Java because TLS PSK is not in the Java JDK :(

For CoAP it's somewhat the default ciphersuite because it's in specified as "mandatory" in the RFC.

It's often the X.509 authentication which are not supported on constrained CoAP nodes and networks.

--
Julien Vermillard

On Mon, Nov 30, 2015 at 4:05 PM, Roger Light <roger@xxxxxxxxxx> wrote:

On Mon, Nov 30, 2015 at 8:30 AM, Julien Vermillard
<jvermillard@xxxxxxxxx> wrote:

> In practice the device communicates regularly with the server (for example:
> every 15 min to once a week) or when some data are ready to send.
> For that CoAP beat MQTT in byte consumption because DTLS PSK both way
> handshake is ~800 bytes where a usual TLS/TCP handshake is 4k~6k and
> piggybacked ack save also few more bytes over TCP ACKs.

For completeness, I just used wireshark to grab packets when
connecting with a mosquitto_sub that had been nobbled not to send any
real data to a mosquitto instance listening with TLS-PSK  over TCP.
The total on the wire byte count was 1419.

Cheers,

Roger

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