Sat (Satellite Technology) HOWTO
 Roberto Arcomano [email protected], Florindo Santoro
 [email protected]
 v1.3, 21 July 2001

 Sat technology is starting to become a great resource for Internet
 users, allowing high bandwidth in downloading and many other interest�
 ing services. This document wants to investigate " State of Art" of
 Sat connections in Linux environment, how to get them speeder and to
 share with many clients. You can found latest version of this document
 at http://www.fatamorgana.com/bertolinux/sat/english <http://www.fata�
 morgana.com/bertolinux/sat/english> and http://www.hack-it.net/How-
 To/Sat-HOWTO.html <http://www.hack-it.net/How-To/Sat-HOWTO.html> .
 ______________________________________________________________________

 Table of Contents



 1. Introduction

    1.1 Introduction
    1.2 Copyright

 2. Background Knowledge

    2.1 What about satellite
    2.2 How does it work?
    2.3 Other technologies
    2.4 What is the max bandwidth?
    2.5 How much does it cost?
       2.5.1 Hardware costs
       2.5.2 Account costs
    2.6 What are the satellites used?
    2.7 What ISPs give Sat Internet Access?
    2.8 What else?

 3. Technical Information

    3.1 General working
    3.2 Frequencies
    3.3 DVB Receiver Card
    3.4 Data Link Level DVB setting
    3.5 TCP/IP working
    3.6 Authentication
    3.7 Services I can use with a sat connection

 4. Requirements

    4.1 Knowledge requirement
    4.2 Hardware
    4.3 Software
    4.4 TV Software
       4.4.1 Under Windows
       4.4.2 Under Linux

 5. Base setup

    5.1 First: mounting
    5.2 Calibrating
    5.3 Double Feed
    5.4 Data-link level adjusting

 6. Configuration under Linux

    6.1 Drivers installation
    6.2 Setting up /etc/dvbd.conf
    6.3 Dvbd daemon
    6.4 How to config EON service
    6.5 How to use Netsystem service
       6.5.1 VPN connection
       6.5.2 Patch for pppd
       6.5.3 Routing settings
       6.5.4 Patch for dvbd.c
       6.5.5 Test it
       6.5.6 Get performance better
       6.5.7 Sharing Netsystem with many clients
    6.6 How to use Sat Node service

 7. Configuration under Windows

    7.1 EON
    7.2 Netsystem

 8. Appendix A - Notes
    8.1 Translation Dynamic IP -> MAC Address
    8.2 TCP Window
    8.3 Download accelerator
       8.3.1 Under Linux
       8.3.2 Under Windows

 9. Appendix B - Well Known Sat ISP setting value

    9.1 EuropeOnLine
       9.1.1 Transponder 113
       9.1.2 Transponder 114
       9.1.3 Transponder 115
       9.1.4 Transponder 103
    9.2 Netsystem
       9.2.1 Transponder 119
    9.3 Sat Node


 ______________________________________________________________________

 1.  Introduction

 1.1.  Introduction

 This document wants to explain something about Satellite technology,
 how it works, what do you need, configuration and how to sharing it
 between several clients. Satellite connections are very different from
 terrestrial ones, they require more attention to setup and also some
 more care to maintain them stable (snow or strong rain could prevent
 you to have a good signal).

 Feedback are welcome, don't hesitate to contact us:
 [email protected] <mailto:[email protected]> and flosan@hack-
 it.net <mailto:[email protected]> .

 1.2.  Copyright

 Copyright (C) 2000,2001 Roberto Arcomano, Florindo Santoro. This
 document is free; you can redistribute it and/or modify it under the
 terms of the GNU General Public License as published by the Free
 Software Foundation; either version 2 of the License, or (at your
 option) any later version. This document is distributed in the hope
 that it will be useful, but

 WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 General Public License for more details. You can get a copy of the GNU
 GPL here <http://www.gnu.org/copyleft/gpl.html>


 2.  Background Knowledge

 2.1.  What about satellite

 In the last few years satellite began to be applied in Internet
 networking, mainly by medium-big ISPs and we have seen it diffused
 between users. Sat connections are a very different kind of networking
 than terrestrial ones, with different timing such as higher RTT (round
 trip time), but also with different bandwidth value, up to 2 Mbps or
 more.

 2.2.  How does it work?

 We can imagine a path like this:


               |||||| S A T E L L I T E  ||||||||
                    /                       /|\
 Downl             /                         |      Uploading
 load             /                          |      from
 to              /(4)                        | (3)  server
 client         /                            |
               /                             |
 SatCard(parabolic antenna)                  |
              |                              |
             \|/                             |
        USER PC ----make request-----> SAT-SERVER <---retrieving---> INTERNET
                          (1)                               (2)



 So first we make the request (1) (using our Internet connection) to
 the Sat-Server, after it will retrieve out info from Internet (2) and
 it will send it to Satellite (3); in the end we would receive data
 from the it (4) to our home using a parabolic antenna and a Sat Card.

 Typically exist 2 kinds of request :


 �  Http

 �  Ftp

 Both of them have a little request data and a much bigger answer size,
 so satellite works very well with it, but with a big time of answer,
 this is the biggest problem of satellite connection (consider a
 typical Sat distance, like 36.000 km, so you would have a time access
 of [ 36000 km / 300.000 km/s = 0.120 s = ] 120 ms you have to add (2
 times, cause first ISPs server send it to, then you download it from)
 to classical Internet time access.

 Recently ISP allows their clients to use also other kind of service,
 like


 �  Chat

 �  Email

 �  News

 and many others.

 There exist also services called " one-way" , which consist in mail
 service , download on-demand (where you make a file reservation to be
 scheduled at some time) and site download: these services are offline,
 so you can access to them without modem (or other kind of) connection.

 2.3.  Other technologies

 We have to report another satellite technology: the 2-way sat
 connection. It uses only the parabolic antenna to contact Internet in
 both 2 directions. Its cost is much higher that 1-way connection.  We
 expect something from it for immediate future, for now it allows a
 bandwidth of 4 Mbit/s in download and 256Kbit/s in upload.

 2.4.  What is the max bandwidth?

 It depends on many factors: ISP purpose, TCP window used, applications
 used by the client and the more important of all, " Internet
 congestion" .

 You can expect a max bandwidth of 1-4 Mbps and a average of about
 10-30 KBytes/s, but I repeat, it depends on many factors.

 Anyway some ISPs tell you they give you a " Max" bandwidth, while the
 average bandwidth could be very lower, due to intra-ISP congestion.

 Some other ISPs guarantees you to have a " Minimal" bandwidth, which
 is more meaningful than " MAX" , cause it is available all the time.

 Please see Appendix A for more about get downloading performance
 better.

 2.5.  How much does it cost?

 We have to distinguish between hardware costs and account costs, the
 first are known, while the second depend on which service you choose
 (" guaranteed" /" not guaranteed" , what bandwidth).

 2.5.1.  Hardware costs

 To install our little satellite system we need:


 1. Sat card

 2. Parabolic antenna

 3. one or more feed (converter)

 Noticed that we need a digital converter to use Internet via
 satellite.

 Sat card costs depends on brand you choose, about 200US$-300US$.

 Parabolic antenna is about 50 US$.

 Converter is about 50US$.

 So we have about 3-400 US$ of hardware cost (maybe you still have to
 add installation cost!!).

 If you want also receiver Crypt service:


 1. CI is about 100 US$.

 2. CAM is about 100 US$-250 US$.

 2.5.2.  Account costs

 Here costs depend on what ISPs give you access, what's peak bandwidth,
 if there is a guaranteed bandwidth (which is more important than peak
 one), what kind of service they give you and so on.

 Also some ISP gives you free access in change of viewing an always
 foreground spot banner (you cannot iconize it!!): in this case you
 will pay when you'll go to buy something showed in banner!!

 Typically account costs are about 100-150 US$ at year for " not
 guaranteed" services and 4-600 US$ or more for guaranteed ones (they
 guarantee you a minimal bandwidth you can use also under congestion
 moments, obviously intra Sat-ISP congestion!! When you go out to
 Internet nobody can guarantee you anything!!).



 2.6.  What are the satellites used?

 When we speak about satellites we mean: Astra (19.2 degree SE),
 Hotbird (13.2 degree SE), new Europestar (45 degree SE), Eutelsat (8
 degree SW), Astra (26E), ArabSat 3A (26E).

 2.7.  What ISPs give Sat Internet Access?

 In Europe we know about 8 ISPs giving Sat access for Internet:


 1. EuropeOnLine - EON <http://www.europeonline.net>

 2. Netsystem <http://www.netsystem.com>

 3. Starspeeder <http://www.starspeeder.com>

 4. Sat Node <http://www.satnode.com>

 5. Eliosat <http://www.eliosat.com>

 6. Falcon Stream  <http://www.falconstream.com>

 7. SkyDSL <http://www.skydsl.com>

 8. OpenSky <http://www.opensky.it>

 9. DirecPC <http://www.direcpc.com> but this use a proprietary sat
    card (this is a first Sat ISP )

 EON gives access for about 150 US$ at year without guaranteed
 bandwidth.

 Netsystem offers its services at " null cost" , you just have to see
 its banner.

 Starspeeder gives access ???

 Eliosat costs 350 US$ at year with a 128 Kbps guaranteed (minimal
 service, see web site for more);in addition it gives 2-way technology
 access for either receive and transmit.

 SkyDSL gives access full-time and it costs about 15 US$ at month with
 128Kbit/s bandwidth, but it allows a bigger bandwidth where you pay
 each Mb downloaded (you can select from 256Kbit/s up to 4Mbit/s), for
 more you can visit its web site.

 IMPORTANT : before subscribing some satellite account, please verify "
 foot of Satellite" and diameter of parabola.

 2.8.  What else?

 With every kind of DVB card you can also receive TV digital channels
 (free channels only) and some cards have support for common interface
 to watch encrypted channel.

 Follows the schema:


 Smart-Card -> CAM -> Common Interface -> Sat Card (with support C.I.)



 CAM Card (there are many standards used for decryption: SECA, IRDETO,
 VIACCESS and others) is the hardware allowing decryption (for TV,
 Radio and Data) while the Common Interface or C.I. (ETSI EN 50221)
 allow connection between CAM and Sat Card.

 3.  Technical Information

 3.1.  General working

 We now try to understand how satellite connection works and at what
 conditions.

 We can imagine a satellite link as a classical Wireless link, I mean a
 link between 2 systems which don't use a real cable to talk each
 other.

 Wireless link is very different from Wired link cause we have some
 additional problems to solve, such as reachability, privacy problems
 and so on. Also there could be weather problems, particularly in snow
 or rain conditions.

 Anyway, we have to consider the first principle behind Wireless
 communication: line of sight free, which is a MUST unless we are
 unable to talk. For more you can see the Wireless-HOWTO
 <http://www.fatamorgana.com/bertolinux/> .

 In sat connections we use a special kind of antenna, a parabolic one,
 that gives us a very high gain in RX, needed to receive satellite
 signal: in fact satellite has a geostational orbital at 36.000 km and
 the only kind of antenna we can use for receiving is just a parabolic
 one.

 3.2.  Frequencies

 Frequency we receive is from 11GHz up to 12.7 GHz (from the satellite
 transponder, the transmitter sending us datas), a very high freq., but
 the feed (converter in the center of the parabola) converts it to, in
 output, 1-2 GHz so that we'll able to send signal to the receiver
 through the cable (up to 40m depending to cable loss).

 3.3.  DVB Receiver Card



 1 GHz Signal --> |RX|--> |ADC| --> |Low Level Network| --> |O.S. TCP/IP Stack|--> Data
                 |____________________________________|
                                 DVB Card



 Now we can imagine a classical RX at 1 GHz receiving analog signals
 from the Sat, converting it to digital signals and giving all to the
 low level network layer (ISO OSI 1,2): here, card firmware builds a 2
 level packet (pretty like ethernet) to be sent to our PC with Linux,
 Windows, or other system, and in the end, we will only have to
 transform it to a TCP/IP packet.

 3.4.  Data Link Level DVB setting

 Here we have to config some settings, directly to the DVB card:


 1. Frequency working, we have to set the satellite frequency (as from
    magazines): it is between 11.8 GHz and 12.8 GHz for example
    12640000 KHz

 2. Symbol rate, measured in symbols per seconds, typically 22 MS/s
    (Mega Symbols per seconds)

 3. Polarization, which is an antenna setting configurable in software:
    possible values are H (Horizontal) or V (Vertical).

 4. PIDs. The PID is used for select a trasmission between many signal
    from same frequency.

 5. Also we have to specify the bitfilter mask, which tells us how
    large is the destination MAC addresses group (bitfilter mask is
    similar to TCP/IP netmask, the only difference is that the
    bitfilter mask is 48 bit size while TCP/IP netmask is 32 bit size).
    Always Internet data is sent with Unicast PID, while Video always
    is sent using Multicast PID .

 6. Calculate MAC address: here we specify what will be our MAC address
    (for our DVB card). You need to do this cause some ISP uses an
    algorithm (see Appendix A for more) which calculates your MAC
    address from your IP address, some other ISP uses your own MAC
    address.

 3.5.  TCP/IP working

 As we said in 2.2 section, first we have to make a request using the
 modem interface (i.e. ppp0 or whatever we use to reach Internet), then
 the answer will return to our DVB interface (dvb0).

 Modern O.S. allow us to receive packets from an input interface,
 different from the output interface from where we made the request: to
 do it we have to " disable" some packets flow control, such as type an

 echo " 0" > /proc/sys/net/ipv4/conf/dvb0/rp_filter (for Linux).

 3.6.  Authentication

 It remains only one thing to complete our description: authentication
 method.

 Some Sat ISPs use the so called " Proxy Authentication" : when you
 used their proxy, you also need to give login and password to continue
 the request (you should have been subscribed some kind of account to
 use their sat service): once done, the ISP use your IP address to
 calculate your MAC address (see Appendix A for more), to which send
 the answer.

 Some other ISPs require you make a VPN connection (using your login
 and password) first, then they will control your registration account
 (where they retrieve your MAC address) and will send data directly to
 (and only to) your card (your MAC address).

 Anyway noticed that you can modify your dvb sat filter value to be
 able to receive packets destined to EVERY mac address (related to a
 single frequency).

 3.7.  Services I can use with a sat connection

 Typically services you can have from sat connections depend on what
 authentication system is used by ISP:


 �  with classical " Proxy Authentication" you can only use HTTP and
    FTP service, while

 �  with VPN connection you have (ideally) no limit to services you can
    use, the only limit is decided by RTT (time access) to satellite,
    about 500-1000 ms average: so you can forget to use " Voice" or
    other " Real Time" services!! (see VoIP-HOWTO
    <http://www.fatamorgana.com/bertolinux> for more). Anyway you still
    can use: mail, chat, telnet, ping, dns and so on.

 4.  Requirements

 Here we will see what we need to try a Sat system.

 4.1.  Knowledge requirement

 For this trying you need some experience in internetworking under
 Linux (as from Net-HOWTO <http://www.linuxdoc.org/HOWTO/Net-
 HOWTO/index.html> ) and a very little of practical experience with
 parabolic antenna and sat systems (you should be able to pointing out
 your antenna, with right angles).

 4.2.  Hardware

 We need:


 1. Parabolic antenna, also taken from an analog system.

 2. Digital converter to be placed in the middle of the antenna.

 3. Receiver card DVB compatible.

 4. a PC to connect to.

 4.3.  Software

 Here you need a


 1. driver for the DVB card working under your O.S. (Linux, Windows or
    other).

 2. right setting to use it

 3. external application in some cases (such as VPN-PPTP client for ISP
    like Netsystem or Starspeeder).

 For the software under Linux you can found the Siemens DVB driver at
 Linux TV Project <http://www.linuxtv.org> .

 4.4.  TV Software

 There is also some Video software used to implement TV reception:

 4.4.1.  Under Windows


 1. MultiDec MultiDec 6.6b
    <http://www.erkner.com/free/digi/MultiDec66b.zip> (free with source
    code)

 2. TPREdit TPREdit <http://come.to/uhura> (for Technotrend)

 3. WinTV DVBs Hauppauge <http://www.hauppauge.de/software.htm> or
    Technotrend <http://www.technotrend.de> (for Siemens compatible
    card, Hauppauge, Technotrend, Technisat, etc... )

 4. WinDVB2000 WinDVB2000 <http://www.odsoft.org/english.html> (about
    19$).



 4.4.2.  Under Linux


 1. gVideo is an application included in Siemens driver

 2. Vdr Video Recoder (good for watch TV)

 5.  Base setup

 5.1.  First: mounting

 The first thing we have to do is to mount our parabolic antenna;

 After we need to pointing it out (searching right degrees from some
 magazine): degrees are always intended from south to east or to west
 for horizontal one and from ground to satellite line for vertical one.
 Classical pointing tools is the compass.

 5.2.  Calibrating

 How can we see if we are right oriented?

 After decided a right range of angles, we have to adjust it measuring
 power level. For such a thing we can


 1. Use for example an analog receiver (which is compatible with
    digital converter) and start to search right degree: when we see
    some imagine we'll get it. I suggest to use analog converter cause,
    maybe, you have one (from precedent installation) and cause it is
    more simple to calibrate it than digital one.

 2. Use a power meter (about 20US$) with sequential lights: at full
    signal all lights turn up.

 5.3.  Double Feed

 You can also install a double feed system (some vendors sell a
 complete kit with standard distance to receive, for example, Astra
 (19.2 SE) with Eutelsat (16 SE) or with HotBird (13 SE).

 For mounting it you have to consider, in addition, that satellite is
 at the opposite side of the converter, like in figure:


               SAT1                 SAT2
                  \                 /
                   \               /
                    \   C1   C2   /
                \    \    \ /    /     /
                 \    \   / \   /     /
                  \____\ /___\ /_____/

                       Top View

                C1 receives from SAT2
                C2 receives from SAT1



 Also, with 2 focus, you would use a diseq.

 5.4.  Data-link level adjusting

 Once we got analog signal we have to adjust our receiver to right
 frequency, PID, speed rate and so on.
 I report here an example of configuration, for EON (EuropeOnLine),
 transponder 114 on Astra satellite (19.2 SE)

 Frequency: 12640 MHz

 Polarization: V (Vertical)

 Symbol Rate: 22000 KS/s

 PIDs:


 �  Unicast: 512 (decimal), 0x200 (hexadecimal)

 �  Multicast: 785, 786, 1041 (decimal), 0x311, 0x312, 0x411
    (hexadecimal), but you should notice that, in many cases, Multicast
    PIDs are taken in automatic.

 We also need another info: what MAC address to assign to our DVB card.

 Again, for EON you can see Appendix A to calculate MAC address from
 dynamic IP address.

 Obviously you need login and password to use ISP service.

 6.  Configuration under Linux

 In this section I will assume to use a Siemens compatible card, like
 an Hauppage WinTV DVB card, for such cards you can download drivers
 from LinuxTV <http://www.linuxtv.org/download/dvb> or DVB-s PCI cards
 under Linux <http://www2.arnes.si/~mthale1/index.html > .

 6.1.  Drivers installation

 Once downloaded drivers, you have to untar them to a directory, enter
 it and type " make" and " make insmod" . To do this you need to have
 actual kernel sources under /usr/src/linux (unless, download them from
 http://www.kernel.org <http://www.kernel.org> and recompile them).

 After made " make insmod" , your system should have DVB modules
 loaded. To unload them type simply " make rmmod" .

 6.2.  Setting up /etc/dvbd.conf

 /etc/dvbd.conf file is used to setup data-link parameters for your DVB
 card. Here main settings:


 �  " power" , which indicates the power to LNB, 1=ON, 0=OFF. Usually
    you should set it to 1, unless you do some kind of cascade between
    more than 1 LNB.

 �  " symbolrate" , this is the symbol rate per seconds, for example
    22.000.000.

 �  " frequency" , at which receiving datas, like 12.640.000.

 �  " ttk" , the 22 kHz signal, almost always to 1.

 �  " diseqc" , used to control the diseq, (it means only when you have
    a diseq controlling 2 or more converters) 0 if none.

 �  " AFC" , usually set to 1.

 �  " polarization" , 1 for horizontal or 0 for vertical one.

 �  " filter_n <PID> <MAC> <BITFILTER>" , where n is intended 0 for
    Unicast and 1-9 for Multicast; PID is expressed in decimal form,
    MAC is the MAC address only valid for Multicast filter and
    BITFILTER is a number which bits represent bytes to mask (for
    example 10 = 2 (bit 1) + 8 (bit 3), so mask will be 00 00 FF 00 FF
    00).


      Example


 ------------------------------------------

 # DVB receiver configuration file, (c) 2000 data planet international

 # standard location in /etc

 # LNB power on=1/off=0

 power 1

 # symbol rate [symbol/sec]

 symbolrate 22000000

 # ASTRA TR 114

 frequency 12640000

 # 22 kHz signal on=1/off=0

 ttk 1

 # diseqc on=1/off=0

 diseqc 0

 # AFC on=1/off=0

 AFC 1

 # polarisation H=1/V=0

 polarisation 1

 # settings for MPE filter, PID and MAC filtering, valid MAC bytes

 filter_0 512

 filter_1 785 00:D0:5C:1E:96:01 48

 filter_2 786 00:D0:5C:1E:96:01 48

 filter_3 1041 00:D0:5C:1E:96:01 48

 -----------------------------------------

 filter_0 has no MAC and no bitfilter values cause the right MAC
 address is calculated from IP address (see Appendix A). We will see
 this setting is OK only for some ISP, for others we'll have to change
 dvbd.c

 6.3.  Dvbd daemon

 Once your /etc/dvbd.conf is ok, you can launch dvbd application,
 which, if executed without -d option, write to stdout signal quality
 level:


 �  Sync MUST be 127 or near it

 �  Vber MUST be 0

 unless you are not well receiving from Sat (check cable and/or dish
 pointing).

 Note:

 Maybe you have to change, in dvbd.h this line

 #define network_device "eth0"

 to

 #define network_device "ppp0"

 depending on which interface you use to reach Internet, eth0 or ppp0:
 type " make" to update binary file and restart dvbd.

 6.4.  How to config EON service

 Now you have a good signal, you can try to use some sat service.

 For EON go at " proxy" setting in Netscape preferences and set under
 HTTP and FTP:

 proxy.xxx.europeonline.net

 and, in " port" 8080 and FTP proxy with " port" 8090.

 where xxx is the transponder number (103,113,114 or 115) you are using
 (see Appendix B for more).

 Now you should be able to navigate wherever you want.... Good
 navigation.

 To share EON service with many clients you can use Squid proxy
 <http://www.squid-cache.org> application, enabling cascade to EON
 proxy.

 For a more complex use of EON, like more complex cascade proxy or
 sharing users, see EON Linux Masquering FAQ Page
 <http://obiwan.hvrlab.org/~faz/eon/eon_masq.html>


 6.5.  How to use Netsystem service

 Netsystem service is a little more complicated than EON under Linux,
 cause, in addition, you need to setup:


 1. VPN connection

 2. patch for pppd (needed only if using pppd <= 2.4.0)

 3. routing settings with simple scripts

 4. patch for dvbd.c

 5. Test it


 6. Get performance better

 7. Sharing Netsystem with many clients

 6.5.1.  VPN connection

 First you need to download VPN PPTP client application
 <http://cag.lcs.mit.edu/~cananian/Projects/PPTP/> .

 After untared, compiled and installed it, you should add an entry to
 your /etc/ppp/pap-secrets and /etc/ppp/chap-secrets files, like that:

 " login" * " password" *

 where " login" and " password" are the same according to Netsystem
 registration <http://css.netsystem.com> .

 6.5.2.  Patch for pppd

 As described at PPTP description
 <http://www.sigpipe.org/~me/vpn/pptp.html> , you need to patch your
 pppd daemon to support connection with Netsystem VPN server (Linux
 server).

 So you have to:


 1. download a recent pppd version
    <ftp://cs.anu.edu.au/pub/software/ppp/>

 2. download and gunzip the correspondent patch for pppd from Here
    <ftp://ftp.binarix.com/pub/ppp-mppe/>

 3. untar pppd in a directory

 4. type " patch -p0 < patch_name"

 5. enter pppd directory

 6. type " make" , " make install"

 6.5.3.  Routing settings

 Now your pppd will be able to working with Netsystem VPN; you can try
 with

 " pptp vpn.netsystem.com debug user <login>"


 where <login> is your login account from Netsystem: you should see, in
 log file (/var/log/messages) ppp1 connection debug info.

 If all is ok you should see ppp1 interface with " ifconfig" command.

 If you still have problems on authentication, please add a " noauth"

 line to your /etc/ppp/options file.

 Once ppp1 interface is up, you should do the following:


 1. type " ifconfig ppp1" and find the IP address (I will call IP) on
    the right of " P-t-P:" string.

 2. delete it from routing table with " route del IP"

 3. add it to ppp0 interface with " route add IP dev ppp0"

 4. delete default gateway from ppp0 with " route del default"

 5. add default gateway to ppp1 with " route add default dev ppp1"

 Points 1-3 are requested cause point-to-point interface are managed,
 under Linux, adding the gateway to the new interface (which is not a
 good idea in this case): unless it you will have a endless loop, cause
 your packet will be continuously encapsulated on itself.

 Points 4,5 are used to make " all internet requests" to ppp1
 interface, so we'll reach the " world" by using VPN connection: this
 could be not optimal in some condition, for example for DNS queries,
 which could be sent directly to avoid useless Sat delay time.

 Instead of manually setup routing configuration you can try using
 these little scripts:

 " netsystem.on" script


 ______________________________________________________________________
 route add IP_DNS1 dev ppp0
 route add IP_DNS2 dev ppp0
 route add -net 212.31.242.0 netmask 255.255.255.0 dev ppp0
 pptp vpn.netsystem.com user <login>
 /bin/sleep 5
 route add default dev ppp1
 ______________________________________________________________________



 " netsystem.off" script


 ______________________________________________________________________
 route del IP_DNS1 dev ppp0
 route del IP_DNS2 dev ppp0
 route del -net 212.31.242.0 netmask 255.255.255.0 dev ppp0
 kill -9 `ps x|grep "pppd"|grep "<login>"|grep -v "ps"|tr " " "\n"|head -n 2`
 rm --force /var/lock/LCK..tty*
 rm --force /var/run/pptp/*
 rm --force /var/run/ppp1.pid
 killall -9 pptp
 ______________________________________________________________________



 IP_DNS1 and IP_DNS2 are ip addresses of your dns servers (primary and
 secondary). <login> is the login name of your Netsystem account. I
 tried it out under kernel 2.4.6 RedHat 7.1 and it works very well
 (without any problems about ppp1 endless loop or similar).

 This line:

 kill -9 `ps x|grep "pppd"|grep "<login>"|grep -v "ps"|tr " " "\n"|head
 -n 2`

 is used to find PID of pppd process talking with VPN server (ppp1
 interface): notice that you cannot just only type " killall pppd"

 cause your ppp0 interface also would go down.



 6.5.4.  Patch for dvbd.c

 After solved problems about PPTP you have to change some line in
 dvbd.c, near the end of it:


 if (strcmp (v, "filter_0") == 0) { if (s != NULL) { unsigned char ip[4];
 dvbcfg[0].status = ON ;
 dvbcfg[0].filter.data[0] = 0x3eff ;
 dvbcfg[0].filter.pid = (__u16) atoi (s) ;
 dvbcfg[0].filter.mode = 0x0c ;
 if (ipget (ip, network_device)) { fprintf(stderr,"Can't get local ip address. Stop.\n") ; return -1 ; }
 syslog (LOG_NOTICE, "Local ip is %u:%u:%u:%u\n", ip[0], ip[1], ip[2], ip[3]);
 dvbcfg[0].filter.data[1] = (ip[3] << 8) | 0x00ff ;
 dvbcfg[0].filter.data[2] = (ip[2] << 8) | 0x00ff ;
 dvbcfg[0].filter.data[6] = (ip[1] << 8) | 0x00ff ;
 dvbcfg[0].filter.data[7] = (ip[0] << 8) | 0x00ff ;
 dvbcfg[0].filter.data[8] = (0x02 << 8) | 0x00ff ;
 dvbcfg[0].filter.data[9] = (0x00 << 8) | 0x00ff ;
 setmac (ip) ; }
 else { dvbcfg[1].status = OFF ; } }



      Now following lines:


 dvbcfg[0].filter.data[1] = (ip[3] << 8) | 0x00ff ;

 dvbcfg[0].filter.data[2] = (ip[2] << 8) | 0x00ff ;

 dvbcfg[0].filter.data[6] = (ip[1] << 8) | 0x00ff ;

 dvbcfg[0].filter.data[7] = (ip[0] << 8) | 0x00ff ;

 dvbcfg[0].filter.data[8] = (0x02 << 8) | 0x00ff ;

 dvbcfg[0].filter.data[9] = (0x00 << 8) | 0x00ff ;


      will be changed to


 dvbcfg[0].filter.data[1] = (MAC[5] << 8) | 0x00ff ;

 dvbcfg[0].filter.data[2] = (MAC[4] << 8) | 0x00ff;

 dvbcfg[0].filter.data[6] = (MAC[3] << 8) | 0x00ff ;

 dvbcfg[0].filter.data[7] = (MAC[2] << 8) | 0x00ff ;

 dvbcfg[0].filter.data[8] = (MAC[1] << 8) | 0x00ff ;

 dvbcfg[0].filter.data[9] = (MAC[0] << 8) | 0x00ff ;

 Where MAC[0]:MAC[1]:MAC[2]:MAC[3]:MAC[4]:MAC[5] is our MAC address
 (according to Netsystem registration).

 After, you have to type " make" and use the new dvbd created.

 Note: to successfully patch the dvbd.c you need to use dvb driver
 version >= 0.8.2, cause older versions have some instability problems.



 6.5.5.  Test it

 Finally, we can test Netsystem under Linux. We can make a " ping
 www.somehostpingable.com" and check the response time: it should be
 between 400 and 2000 ms.

 If you still have problems, you should control if all is OK with VPN
 interface:


 1. open your preferred network sniffer (for example Ethereal
    <http://www.ethereal.net> ) and starts to analyze " ppp0" interface
    (ppp0, not ppp1!!)

 2. make a ping

 If VPN is ok you should see 2 (or maybe 1) GRE-Encapsulated packets
 each second, endless. If you cannot view anything your VPN is not
 correctly working: stop it and restart it.

 6.5.6.  Get performance better

 Once you setup all things you NEED to use (particularly with Netsystem
 service) some " download accelerator" to get performance better:
 please see Appendix A for more.

 6.5.7.  Sharing Netsystem with many clients

 To do this you can enable " IP Masquering" , allowing your client to
 use VPN like a normal Internet interface; main problem is that our
 satellite connection is very good for download while it has bad
 performance for just browsing web pages (or other service more
 interactive than downloading).

 You can think to use Squid proxy <http://www.squid-cache.org> or Socks
 proxy <http://www.socks.nec.com/> , but you don't solve your problems,
 cause even now ALL your request would be forwarded to same interface,
 VPN.

 The solution is to use 2 routing tables, one using direct line
 interface and the other using VPN one. So you can do like this:


 1. be sure of have installed " iproute2" commands (for example type "
    ip" on shell and control if it tells you something), for more see
    Linux 2.4 Advanced Routing HOWTO
    <http://www.linuxdoc.org/HOWTO/Adv-Routing-HOWTO.html> .

 2. be sure of have started Netsystem service and annotate ppp1
    interface IP address, we'll call it LOCALIP.

 3. type: " echo " 210 sat" >> /etc/iproute2/rt_tables" , to more
    comfortable call " sat" rule 210

 4. type: " ip rule add from LOCALIP table sat" , to create table "
    sat"

    relative to all requests coming from LOCALIP IP address.

 5. type: " ip route add default dev ppp1 table sat" , to send all "
    sat" requests (see above) to ppp1 interface.

 6. if you use Socks proxy <http://www.socks.nec.com/> be sure to set,
    in sockd.conf file, " external" to LOCALIP.


 7. if you use Squid proxy <http://www.squid-cache.org> be sure to set,
    in squid.conf file, " tcp_outgoing_address"

    to LOCALIP.

 Once done all that, you will notice to have 2 kind of working: without
 any proxy your clients will ask to direct line, while by using proxy
 (squid or sockd) the request will be forwarded to VPN interface and,
 definitely, toward satellite.

 Notice that maybe you wish to use sockd instead of squid, cause
 satellite requests are typically used for download (while squid is
 typically used for browsing...).

 What happens with iproute2 commands is that, when you ask for an
 address to sockd or squid, relative proxy (using IPLOCAL IP address,
 bound at run-time by proxy network daemon) request enters the TCP/IP
 stack where kernel will forward it (thanks to point 4 above) to sat
 table and, definitely (by using point 5) to ppp1 interface. All other
 rules will be forwarded to classical default route (I mean across ppp0
 interface or whatever other interface for direct Internet).

 6.6.  How to use Sat Node service

 You have to follow all instructions as for Netsystem.

 Before enabling VPN connection, you need to type:


 �

 �  to reach the vpn server just through ppp0

 �

 �  route to reach every place.

 What really changes from Netsystem is that, we don't force VPN gateway
 (212.56.224.34, IP on the right of ''P-t-P'' in ppp1 interface) on
 ppp0 interface, but we force another IP (212.56.224.36). All other
 things should not change.

 Thanks to Ricardo Santiago Mozos and Norberto Garcia Prieto.

 7.  Configuration under Windows

 7.1.  EON

 Hauppage WinTV has DVB-DATA application that allows to specify data-
 link settings.

 7.2.  Netsystem

 First you need to install VPN capabilities.

 In addition you need to download Netsystem software (always foreground
 spot banner) and launch it: after you should not be able to use
 Netsystem service: you can download it from here
 <http://bertolinux2000.interfree.it/Netsystem/Netsystem.zip>


 8.  Appendix A - Notes



 8.1.  Translation Dynamic IP -> MAC Address

 The translation used by some ISPs to calculate MAC address (which need
 to have your DVB card to receive their packets) is:

 00 : 01 : IP[0] : IP[1] : IP[2] : IP[3]

 where

 IP[0].IP[1].IP[2].IP[3] is your dynamic IP address.

 This feature is used, for example, by EON.

 8.2.  TCP Window

 Satellite connections are an interesting example of very high RTT
 (round trip time, access time): another example is the Mars - Earth
 communication or also the Moon - Earth one.

 These connections have a very bad feature: very low interactively.

 Typical network (or digital, generally) connections use the so called
 transmission " window" , which represents the data buffer can be sent
 before waiting for an answer. In TCP/IP protocol stack this is the TCP
 Window.


                   ----------------------
   | - - - - - - - > can continue |-|-|-|---->
   |               ----------------------
   |             Buffer sendable before confirm
   |
   | - - - - - - - <----------------------
                    Confirmation Answering



 Now, if our communication has an high access time and if we had a
 little TCP Window we would lose very much time only waiting for the
 data confirmation (ACK), so the real bandwidth would decrease (for
 example if you have a 16KB TCP window, typical of Windows systems and
 a RTT of 400 ms, you cannot overcome 16KB/0.4 = 40 KB/s)

 Solution is to use a very high TCP Window (such as 256 KB or some MB).

 Unfortunately, under many systems, is not so simple to have a great
 TCP Window, so, in latest years, it starts to appear new applications
 (" download accelerators" described in next section) that split in
 many pieces a file and download all them in the main time: this is
 just equivalent to download only one file with a single piece size,
 avoiding the RTT problem.

 8.3.  Download accelerator

 We report here some useful link to so called " download accelerator"

 which is an application that does 2 things:


 1. resuming session management, it allows stopping downloading and
    restarting later (this can be done thanks to " resuming feature"
    introduced in Http and Ftp server, which allows you to specify at
    what byte number start to download).

 2. splitting, divide the file in many pieces and let them start in a
    multithreaded fashion.
 As we saw in the previous section, a download accelerator allows us to
 increase satellite bandwidth.

 8.3.1.  Under Linux


 �  Aria <http://aria.rednoah.com/>

 8.3.2.  Under Windows


 �  FlashGet <http://www.amazesoft.com>

 �  GetRight <http://www.getright.com>

 �  Mass Downloader <http://www.metaproducts.com>

 9.  Appendix B - Well Known Sat ISP setting value

 9.1.  EuropeOnLine

 EON sends data from Astra satellite (19.2 SE).

 MAC address is calculated from IP address (see Appendix A).

 It uses " Proxy Authentication" .

 Follows the 4 transponder setting:

 9.1.1.  Transponder 113


 �  Frequency: 12633.250 MHz,

 �  SRate : 22 MS/s

 �  Polarization: Horizontal

 �  Unicast PID: 512 (decimal)

 9.1.2.  Transponder 114


 �  Frequency: 12640 MHz,

 �  SRate : 22 MS/s

 �  Polarization: Vertical

 �  Unicast PID: 512 (decimal)

 9.1.3.  Transponder 115


 �  Frequency: 12662.750 MHz,

 �  SRate : 22 MS/s

 �  Polarization: Horizontal

 �  Unicast PID: 512 (decimal)

 9.1.4.  Transponder 103



 �  Frequency: 12461 MHz,

 �  SRate : 27.5 MS/s

 �  Polarization: Horizontal

 �  Unicast PID: 512 (decimal)

 9.2.  Netsystem

 Netsystem uses Astra satellite (19.2 SE) to send data .

 MAC address used is your real MAC address DVB card.

 It uses VPN connection.

 Follows data setting:

 9.2.1.  Transponder 119


 �  Frequency: 12721 MHz

 �  SRate: 22MS/s

 �  Polarization: Horizontal

 �  Unicast PID: 451 (decimal)

 9.3.  Sat Node

 Sat Node uses Astra satellite (19.2 SE).


 �  Frequency: 12603.750 MHz

 �  SRate: 22MS/s

 �  Polarization: Horizontal

 �  Unicast PID: 302

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