nRF91, RAI with PPP

[MattiasE]

Hello

We are developing a new product using the nRF54LM20 as a main MCU and nRF9151 as the modem. We are looking into using the IP-stack in the main MCU, so running the modem in CMUX/PPP mode using the serial modem application provided by you (https://github.com/nrfconnect/ncs-serial-modem).

I have a few questions regarding this:

1. To my understanding, the only API for RAI is the socket option API (nrf_setsockopt exposed via #XSOCKETOPT). This makes it impossible to use RAI in combination with PPP since there are no sockets on the modem, right?
   1. The modem aggregates the RAI statuses from all sockets and determines what to do (request release from network or not). In principle, it should be possible to let the user do its own aggregation and signal if more data is expected or not to the modem, via for example an AT-command. Do you have any plans to extend the RAI functionality so RAI can be used in combination with CMUX/PPP?
2. Are there any other reasons why we should avoid using the CMUX/PPP approach?

Best regards

Mattias

[Øyvind]

Hello Mattias, 

To my understanding, the only API for RAI is the socket option API (nrf_setsockopt exposed via #XSOCKETOPT). This makes it impossible to use RAI in combination with PPP since there are no sockets on the modem, right?

1. The modem aggregates the RAI statuses from all sockets and determines what to do (request release from network or not). In principle, it should be possible to let the user do its own aggregation and signal if more data is expected or not to the modem, via for example an AT-command. Do you have any plans to extend the RAI functionality so RAI can be used in combination with CMUX/PPP?

RAI is currently not supported for the PPP socket, and there are no plans on the roadmap to enable this functionality. To date, this is the first request we have received for this feature.

Are there any other reasons why we should avoid using the CMUX/PPP approach?

It's hard to assess this without additional context. The original decision to use PPP was likely driven by specific technical or application requirements. Understanding what the solution is trying to achieve, along with the protocols and architecture involved, would help us provide a more informed recommendation.