Just a follow up on my previous postings where I reported a Siemens
MC35 hanging while dialing up to a GPRS connection. Now I have
changed to a Nokia 30 terminal and it is showing the same symptoms.
I know now that when the PPP negotiations go on and at the point where
the modem suggests an IP address to use that the network should reject
and suggest its own which the modem acknowledges as follows.

sent [IPCP ConfReq id=0x1>]
rcvd [IPCP ConfReq id=0x0 ]
sent [IPCP ConfAck id=0x0 ]
rcvd [IPCP ConfNak id=0x1
sent [IPCP ConfReq id=0x2
rcvd [IPCP ConfAck id=0x2

Sometimes it happens that the modem keeps sending
sent [IPCP ConfReq id=0x1>]
sent [IPCP ConfReq id=0x1>]
sent [IPCP ConfReq id=0x1>]

and never gets a reply. It seems that there is some packet
sequencing mismatch between the modem and the network that causes this
and the only way to fix it is to turn the modem off and switch it back
on (completely deregister from the network).

I have however not found a bullet proof way of turning the modem off
and on. I donīt understand why modem makers donīt have a reset
command that will turn the phone off and on. On an interesting note
I tried using a R520m and as soon as I break a PDP Context the phone
automatically resets (powers down/up).... Maybe Ericsson has seen
this problem in dial-up happening and this is their way of assuring
you are derigestered from the network.