Re: [mosquitto-dev] eDRX and MQTT

[john rubis <john.rubis@xxxxxxxxxxx>]

Yes, that is what I mean. The modem is only checking for messages at the set eDRX interval. In between intervals, the device is not reachable. When the modem does check in with the network, the application processor remains asleep. The application processor is only woken up if a message was received. This is a very quick (very low power) check-in with the network. The eDRX interval is settable from 5.12s to 10485.76s in 16, non-linear steps.

eDRX differs from PSM (Power Save Mode) where the application processor wakes up and drives a connection to check for messages pending on the broker or to post a message to it. This connection process takes longer and consumes a lot more power. 

I was able to log the TCP traffic on my server today and observed the retries occurring with the exponential backoff that you mention.

John

-----Original Message-----
From: Greg Troxel <gdt@xxxxxxxxxx> 
Sent: Monday, February 25, 2019 6:57 PM
To: john rubis <john.rubis@xxxxxxxxxxx>
Cc: Frank Pagliughi <fpagliughi@xxxxxxxxxxxxxx>; General development discussions for the mosquitto project <mosquitto-dev@xxxxxxxxxxx>
Subject: Re: [mosquitto-dev] eDRX and MQTT

john rubis <john.rubis@xxxxxxxxxxx> writes:

> I am currently using a normal TCP connection and my hope was to keep 
> that open between eDRX cycles because that is the connection I 
> expected a message would be received on that will wake the device up. 
> So yes, at the eDRX interval the modem would detect the inbound 
> traffic and wake up the device.

I think you are saying:

  modem goes to sleep

  packet is sent by server

  (time passes)

  modem wakes up on schedule

  more or less immediately, the packet that was sent is received
  whatever back and forth happens


Is that what you mean?


I think Frank was asking if the sent packet would cause a wakeup not on the regular schedule.