ppp implementation over GPRS

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Hi All,

I am trying to implement PPP. I appear to be getting as far as the PAP,
but then the server just waits for about 10 seconds and disconnects
unless I 'poke' it with a request for an IP address. This suggests that
I haven't actually done enough LCP to get to the NCP phase.

Any ideas or references?

Regards
Rocky


Re: ppp implementation over GPRS
I am not sure there was such a thing like "too few" LCP options (but
last time I did ppp was > year ago). If you get an IP in reply to your
request, things seem pretty much normal - the other side may well
assume a 10 seconds timeout, i.e. if you did not request (or state)
an IP address, something is assumed to have gone wrong on either side.
 As for references, those I used you obviously already have
(rfc1661 1662 etc :-). Good luck with your implementaton.

Dimiter

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Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
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Re: ppp implementation over GPRS
This occured to me after posting my former reply.
There can actually be "too few" LCP options - namely 0.
Both sides must have received a "configure-ack" before
you can move further form the LCP stage.

Dimiter

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
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Re: ppp implementation over GPRS
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Hi Didi,
thanks - I have read thru the RFCs, but I must admit was trying to hack
some code to get it going quickly. The thing is that when I do an
ethereal trace off a setup on my PC the server _offers_ its IP address
after authentication and then the PC negotiates for its IP by
requesting '0.0.0.0'. In my implementation I don't get the intial
offer. Also, because I'm on a private APN I should be getting a
specific IP, but I actually get some othe IP - as if I haven't logged
in properly. I suppose that is a major clue!

Regards - Rocky


Re: ppp implementation over GPRS

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Hi Didi - thanks for input. The problem was that is was not doing the
ATD command correctly. ATD*99# connects using 'internal default
settings' and does not default to the setting that I had set up.  I had
to change to ATD*99**ppp*1# and then I got the correct IP address.

Regards - Rocky


Re: ppp implementation over GPRS

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What do you mean implementing PPP over GPRS?
AFAIR the server side state machine is distributed between the handset and
the GGSN.  This means, that you can't realy talk about the phases.

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If I remember well, then the handset always returns with successful
authentication, but if the authentication fails in the GGSN, or something
timeouts, then you'll see a simple disconnect.

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3GPP standards.  (At least I used those when I implemented PAP processing
in a GGSN a couple of years ago.)

Regards

ImRe

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