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It seems that GPRS does not support PAP. It asks for CHAP (0xc223).
I configured my phone as a standard modem and logged the stream. In reply to C223 packet from phone, the PC sent
7E 80 FD 01 05 00 0A 12 06 00 00 00 01 3E 62 7E
It is a CCP. The phone in response sends a
C021 08 (protocol Reject)
The PC immediately proceeds to IPCP (0x8021)
Does it mean that all Authentications are bypassed??
I have tested the connection from PC to GPRS phone using PPP. There is no authentication. Here is what happens.
1. Dialup
2. PPP-LCP is negotiated.
3. PC sends a PAP packet with user and pw
4. GPRS phone replies with a "Reject protocol"
5. PC starts PPP-IPCP negotiations
6. Phone responds and IP settings are assigned.
7. IP communications begin.
The default authentication is CHAP. But you can send a reject packet and skip to IPCP. This makes sense. GPRS service is charged to the SIM. There is no point of authentication.
I wonder why dont all GPRS phones and modems use SLIP instead of PPP. It is much more practical in this case.
I tried another sequence. The phone asked for CHAP during LCP. I replied with NAK. Phone asked for PAP, I sent ACK. Then when LCP is done, I send a PAP packet with user/pass. The phone ACKs and IPCP begins. I am using siemens A65, 8051, Telenor.
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