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OSDA Technical Information

Introduction

Opensky Direct Access (OSDA) is a technology which allows an Opensky user to establish a tunnel between his computer and the Opensky platform. The tunnel is asymmetric, as the forward path (user to platform) is different from the return path (platform to user). Normally, all user traffic will be transported inside this tunnel. Using this technology, most protocols will be automatically transported over satellite without the need for special proxy configurations.

The main features of OSDA are:

• support for users which are assigned a private IP address from their ISP, or that otherwise NAT-ted or PAT-ted by their ISP; these users cannot currently use the Opensky service.
• simplify the configurations required on the client side;
• enlarge the number of protocol and applications supported by Opensky.

OSDA allows two types of tunnels to be established, according to the underlying protocol:

• PPTP: this type of tunnel is easy to configure but it is not compatible if the user is in a network which does not fully support the GRE protocol (as it is the case with most GPRS providers, for example);
• L2TP: this type of tunnel requires a change in the Windows registry. However, it is compatible with NAT/PAT.

Note that in any case the tunnel is not encrypted: this means that data is sent in the clear over the Internet or over the satellite. In order to achieve confidentiality of data, the user should use secure protocols such as HTTPS, SSL, or application-layer security tools such as SSH, PGP, etc.

OSDA Configuration (for users)

OSDA-PPTP for Windows

Notice that Windows95 requires special package (available for free from Microsoft site) in order to support PPTP connections.

• create a new connection with the New Connection Wizard;
• select "Virtual Private Network (VPN)" as type of connection;
• select, if you want, a dial-up to establish automatically (usually your GPRS connection);
• in “Host name or IP address” insert osda.eutelsat.net;

after creation, edit the Properties in the following way:

• in the “Network” tab:
• untick all protocols except TCP/IP;
• in the “Security” tab:
• untick the checkbox “Require data encryption (disconnect if none)”

You can connect by selecting the new connection and using your Opensky login and password;

• you do not need to make "satlogin" from the Satlogin page;
• you do not need to set any proxy in your browser;

OSDA-PPTP for Linux

• refer to the site pptpclient.sourceforge.net
• on a typical RH9 installation, the following packages are required:
• ppp-2.4.2_cvs_20030610-1.i386.rpm
• kernel-mppe-2.4.20-8smp.i686.rpm
• actual name depends on your kernel
• can be generated using kernelmod-0.7.1.tar.gz
• pptp-linux-1.3.1-1.i386.rpm
• pptp-php-gtk-20030505-rc1.i386.rpm

After installing all required packages, run pptpconfig.

OSDA-L2TP for Windows

• create a new connection with the New Connection Wizard;
• select "Virtual Private Network (VPN)" as type of connection;
• select, if you want, a dial-up to establish automatically (usually your GPRS connection);
• in “Host name or IP address” insert osda.eutelsat.net;
• after creation, edit the Properties in the following way:
• in the “Network” tab:
• chose "Layer 2 Tunnelling Protocol (L2TP/IPSEC)" as type of VPN;
• untick all protocols except TCP/IP;

edit the Windows Registry in one of the following ways:

• either double-click on the provided file “ProhibitIpSec.reg”;
• or manually launch “regedit.exe”, then create the key HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ RasMan \ Parameters \ ProhibitIpSec as a DWORD with value ‘1’;

REBOOT YOUR COMPUTER (important);

• after reboot, you can connect by selecting the new connection and using your Opensky login and password;
• you do not need to make "satlogin" from the Satlogin page;
• you do not need to set any proxy in your browser;
  
• Notice that the change in the Registry will completely disable IPSEC from your computer. If you need IPSEC for other uses, double-click on the attached file "RestoreIpSec.reg" and reboot.

OSDA-L2TP for Linux

Some L2TP clients do exist for Linux. However, we do no have precise configuration instructions yet. You can try the following URLs:

• freshmeat.net/projects/rp-l2tp
• www.l2tpd.org

OSDA Use (for users)

The use of OSDA is very simple once the DVB adapter is correctly configured.

If the user does not use the Opensky Client software:

• configure the DVB adapter with your unicast PIDs;
• double-click on the OSDA connection, and insert the usual Opensky login and password;
• after connection, all Internet traffic will be directed to the OSDA tunnel, and data will be received by satellite. No explicit Satlogin or proxy configuration is required.

If the user uses the Opensky Client software below version 1.6, user should upgrade to 1.6

Opensky Client Software version 1.6 will automatically support transponder configuration for OSDA use. The setup will also create the OSDA dial-up connections.

Known issues

• if the DVB card configuration is wrong (e.g. missing PID) the OSDA tunnel will open normally, but browsing will be impossible;
• if the user is behind a NAT or PAT router (often the case when the use is assigned a private IP address such as 10.* or 192.*), then PPTP negotiation will fail with errors (such as –901). Use L2TP instead.
• opening the tunnel will give the error “login or password incorrect” for any problem (expired contract, no more traffic available, account suspended, ...). To receive a full error message you have to use the standard Satlogin mechanism;
• OSDA does not support multipath routing (aka terrestrial return);
• modifying the Windows registry (for OSDA-L2TP tunnels) may interfere with other VPN-type connections of the user;
• the speed using a GPRS uplink is not very high (~100 kbps) due to limitations of the GPRS uplink bandwidth.
• if your DNS is not able to resolve the name osda.eutelsat.net, you can use its IP address 193.251.135.97. It is strongly suggested to use the name instead of the IP, as the IP address will change in the future.
• when using OSDA, the mail server of the user may refuse to send e-mails, as they appear to be sent from a foreign address. To solve this, the user must either:
• configure his mail client to use the host multi1.eutelsat.net (IP 193.251.135.85) as SMTP server, instead of the ISP SMTP server. [This host will soon be renamed as smtp.eutelsat.net or mail.eutelsat.net]
• insert a route to reach the ISP SMTP server via the normal PPP connection rather than via the OSDA tunnel. For example, if the ISP SMTP server is smtp.isp.com, and the address of the current PPP connection is 1.2.3.4, this command will do the job under Windows:
• route add smtp.isp.com 1.2.3.4

Conclusions

OSDA is a new technology, which should be beneficial to all Opensky users, because it is both powerful and simple to use. We invite Resellers to test the technology in their labs, or with selected customers, and to report any comment or problem encountered. A Reseller should send any communication to the Opensky Support.

As usual, Opensky Support cannot accept, and will silently ignore, mails coming directly from end customers, as well as too generic comments, which do not provide any useful means to track the problem.

©2008 BeyonDSL.net Ltd

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