Iphone

Question: Is it necessary to use LCP with PPP while dialing in a stand alone mode? I ask this because I have been working with a developer using a wavecom modem, who indicated that during the PDP context activation, the modem was set for auto-connect mode by setting either AT$AREG=2 (or manually activate by sending AT+CGACT=1,1 commands) - you don't have to send the dial string (*99#). This is done automatically inside the modem and it tries to negotiate the PDP context activation with the network. In this case the client would still allow user to enter AT commands even after the PDP context activation is established - unless the modem is setup for PAD mode (which was not the case with the client).
In anycase, the resolve to this situation was for the developers to create a PPP connection by only sending CHAP and IPCP, omitting LCP. Can anyone provide a reason why this would work? In fact does anyone have any information detailing how PPP, LCP, IPCP works in the GPRS environment. I have a feeling I and my colleagues are not understanding the actual procedures.

Iphone

I believe that a PPP session only exists if you want it to exists: whem the mobile attaches to the GPRS network (through SGSN node) and activates the PDP context, it gets a mobile IP that id's the MT in the GPRS network... Then it can dial-up the remote network (there'll be a dial string and the subsequent CONNECT, PPP session, etc.). But before you can dial a remote network using the GPRS backbone you must activate a PDP (it's the routing mechanism that supports the very GPRS network model). Hear this: whwn you dial-up using GPRS, the mobile will AUTOMATTICALLY attach to the GPRS network and activate the PDP (if any), and only then dial the network...

So, resuming:

1. attach to the GPRS network
2. activate a PDP context (it routes the IP traffic to the APN that supports your SIM card)
3. dial and establishe a PPP tunnel