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Category:L2TP Handover: Difference between revisions

Category:L2TP Handover (view source)

Revision as of 21:01, 24 October 2010

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This page documents my experiments setting up an LNS for my Revmobile data SIMs.
 
For the LNS, I used openl2tpOpenL2TP running on Linux (Debian 'squeeze'). I did some experiments with xl2tpd as well.
 
=SIM Configuration=
 
At the moment you need to ask RevK to set up L2TP handover on a SIM. You will need to give him the ICCID, the IP address of theyour LNS, and a shared secret if you want to do tunnel authentication. More on that later.
 
=Setting up OpenL2TP=
 
The OpenL2TP download page [http://www.openl2tp.org/downloads heredownload page] only mentions version 1.6. This didn't compile on squeeze without building the l2tp configuration parser by hand with byacc first. If you go to [ftp://ftp.openl2tp.org/releases/openl2tp-1.6 the websiteFTP site] there is actually a version 1.7 available, which compiles straight out of the tarball.
 
This is the configuration I'm using -- with my IP addresses and tunnel secret removed, naturally! If you don't want tunnel authentication, leave out the 'secret=' and 'auth_mode=' lines.
tunnel profile modify profile_name=doubtless \
secret=<your secret here> \ # leave out if you don't want tunnel authentication
auth_mode=challenge \ # leave out if you don't want tunnel authentication
src_ipaddr=<your LNS IP> \
our_udp_port=1701 \
=Musings=
 
AuthenticationPPP withover GPRS connections is a bit, well, weird. The PPP connection that pppd on your laptop establishes is not all the way through to your LNS as you might expect. It isn't even terminated in the mobile network -- it's actually terminated on the modem. What this means is that the username and password you give to pppd are verified by the modem -- which just accepts anything you supply.
 
The proxy authentication username that the LAC presents is a UK 07xxx phone number. It also presents a CHAP authentication ID, challenge and response. These are ignored unless you enable allow_ppp_proxy. I haven't yet worked out what the secret is that is being used to generate the response. It isn't the l2tp tunnel authentication secret, the proxy authentication username, the ICCID, or the password that was supplied to the modem.
The 'calling number' and 'called number' in the incoming call request are the SIM's ICCID.
 
The two devices that I've been using -- a Vodafone (Huawei) K4505 and a Nokia E51 -- both behave noticeably differently when it comes to PPP and particularly IPCP.
 
=Things to do=
Met
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