> 4.3.2 | DLC Establishment

> The multiplexer control channel must be set up as the first channel followed by all other DLCIs. To do so, a SABM frame (see Section 4.2.3) must be sent to the module.
> The module responds either with a UA frame if the DLCI was set up, or with a DM frame if the DLCI was not set up.
> No provision is made for repeating the request if a response is not received.
> The state machine requesting the multiplexer control channel DLCI = 0 is the "initiating station", while the other is called the "responding station".
> Figure 8: DLC establishment