connecting to gprs network through gprs/gsm modem in linux using pppd and chat

I'm using telit GC864-DUAL-V2 modem.

I'm trying to connect to a gprs network with chat and pppd in Linux. In that I'm getting the error message saying that "LCP: timeout sending Config-Requests" from pppd. I've tried increasing lcp-max-configure option in the pppd. Then also I'm getting the same error message.

Can anybody give some suggestions to rectify this issue?

The following is the verbose message logs I've obtained from pppd.

PPPD LOG OBTAINED:

pppd /dev/ttyUSB0 115200 modem lock connect '/usr/sbin/chat -v -s -f /etc/ppp/chatscript' debug logfd 1 nodetach no开发者_开发百科auth defaultroute 
timeout set to 10 seconds
abort on (\nBUSY\r)
abort on (\nNO ANSWER\r)
abort on (\nERROR\r)
abort on (\nNO CARRIER\r)
timeout set to 35 seconds
send (ATZ^M)
expect (OK)
ATZ^M^M
OK
 -- got it

send (ATX3^M)
expect (OK)
^M
ATX3^M^M
OK
 -- got it

send (AT&K0^M)
expect (OK)
^M
AT&K0^M^M
OK
 -- got it

send (AT+CGDCONT=2,"IP","airtelgprs.com"^M)
expect (OK)
^M
AT+CGDCONT=2,"IP","airtelgprs.com"^M^M
OK
 -- got it

send (AT+CGATT=1^M)
expect (OK)
^M
AT+CGATT=1^M^M
OK
 -- got it

send (ATD*99***2#^M)
expect (CONNECT)
^M
ATD*99***2#^M^M
CONNECT
 -- got it

Serial connection established.
using channel 7
Using interface ppp0
Connect: ppp0 <--> /dev/ttyUSB0
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <asyncmap 0x0> <auth pap> <magic 0x23dd4e00> <pcomp> <accomp>]
No auth is possible
sent [LCP ConfRej id=0x1 <auth pap>]
rcvd [LCP TermReq id=0x2 00 00 00 00 00 00]
sent [LCP TermAck id=0x2]
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xdd04133c> <pcomp> <accomp>]
LCP: timeout sending Config-Requests
Connection terminated.
Modem hangup

I've added AT#GAUTH=0 into my chat script. Then I was able to connect without any issues.

NOTE:

• AT#GAUTH - command sets the authentication type either for PPP-GPRS and PPP-GSM connection. Its factory default is PAP authentication enabled. For further details refer telit GC864-DUAL-V2 AT reference manual.

In my case without AT#GAUTH=0 added into chat script modem was expecting authentication packet from the peer. But in my case peer (airtel) it does not require any authentication.So it did not send any packet. So in the host side I was getting timeout message from pppd.

I hope this may help somebody like me who is searching for answers.