<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <HTML> <HEAD> <META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9"> <TITLE>Sat (Satellite Technology) HOWTO: Background Knowledge</TITLE> <LINK HREF="Sat-HOWTO-3.html" REL=next> <LINK HREF="Sat-HOWTO-1.html" REL=previous> <LINK HREF="Sat-HOWTO.html#toc2" REL=contents> </HEAD> <BODY> <A HREF="Sat-HOWTO-3.html">Next</A> <A HREF="Sat-HOWTO-1.html">Previous</A> <A HREF="Sat-HOWTO.html#toc2">Contents</A> <HR> <H2><A NAME="s2">2. Background Knowledge</A></H2> <H2><A NAME="ss2.1">2.1 What about satellite</A> </H2> <P>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. <H2><A NAME="ss2.2">2.2 How does it work?</A> </H2> <P>We can imagine a path like this: <P> <PRE> |||||| 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) </PRE> <P>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. <P>Typically exist 2 kinds of request : <P> <UL> <LI>Http</LI> <LI>Ftp</LI> </UL> <P>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. <P>Recently ISP allows their clients to use also other kind of service, like <P> <P> <UL> <LI>Chat </LI> <LI>Email </LI> <LI>News </LI> </UL> <P>and many others. <P>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. <H2><A NAME="ss2.3">2.3 Other technologies</A> </H2> <P>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. <H2><A NAME="ss2.4">2.4 What is the max bandwidth?</A> </H2> <P>It depends on many factors: ISP purpose, TCP window used, applications used by the client and the more important of all, "Internet congestion". <P>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. <P>Anyway some ISPs tell you they give you a "Max" bandwidth, while the average bandwidth could be very lower, due to intra-ISP congestion. <P>Some other ISPs guarantees you to have a "Minimal" bandwidth, which is more meaningful than "MAX", cause it is available all the time. <P>Please see Appendix A for more about get downloading performance better. <H2><A NAME="ss2.5">2.5 How much does it cost?</A> </H2> <P>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). <H3>Hardware costs</H3> <P>To install our little satellite system we need: <P> <OL> <LI>Sat card</LI> <LI>Parabolic antenna</LI> <LI>one or more feed (converter)</LI> </OL> <P>Noticed that we need a digital converter to use Internet via satellite. <P>Sat card costs depends on brand you choose, about 200US$-300US$. <P>Parabolic antenna is about 50 US$. <P>Converter is about 50US$. <P>So we have about 3-400 US$ of hardware cost (maybe you still have to add installation cost!!). <P>If you want also receiver Crypt service: <P> <OL> <LI>CI is about 100 US$.</LI> <LI>CAM is about 100 US$-250 US$.</LI> </OL> <H3>Account costs</H3> <P>Here costs depend on what ISPs give you access, what's peak bandwidth, if there is a guaranteed bandwidth (which is more important than peak one), what kind of service they give you and so on. <P>Also some ISP gives you free access in change of viewing an always foreground spot banner (you cannot iconize it!!): in this case you will pay when you'll go to buy something showed in banner!! <P>Typically account costs are about 100-150 US$ 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!!). <H2><A NAME="ss2.6">2.6 What are the satellites used?</A> </H2> <P>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). <H2><A NAME="ss2.7">2.7 What ISPs give Sat Internet Access?</A> </H2> <P>In Europe we know about 8 ISPs giving Sat access for Internet: <P> <OL> <LI> <A HREF="http://www.europeonline.net">EuropeOnLine - EON</A></LI> <LI> <A HREF="http://www.netsystem.com">Netsystem</A></LI> <LI> <A HREF="http://www.starspeeder.com">Starspeeder</A></LI> <LI> <A HREF="http://www.satnode.com">Sat Node</A></LI> <LI> <A HREF="http://www.eliosat.com">Eliosat</A></LI> <LI> <A HREF="http://www.falconstream.com">Falcon Stream </A></LI> <LI> <A HREF="http://www.skydsl.com">SkyDSL</A></LI> <LI> <A HREF="http://www.opensky.it">OpenSky</A></LI> <LI> <A HREF="http://www.direcpc.com">DirecPC</A> but this use a proprietary sat card (this is a first Sat ISP )</LI> <LI> <A HREF="http://www.xanticbroadband.com/">http://www.xanticbroadband.com/</A></LI> </OL> <P>EON gives access for about 150 US$ at year without guaranteed bandwidth. <P>Netsystem offers its services at "null cost", you just have to see its banner. <P> <P>Starspeeder gives access ??? <P>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. <P>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. <P>IMPORTANT : before subscribing some satellite account, please verify "foot of Satellite" and diameter of parabola. <P>OpenSky started before summer 2001 in its "beta test": it allows you to try the sat service downloading at maximum 300 MB at month (free). To register you need to go at <A HREF="http://www.opensky.it/cc/index.asp?f=registrazione.htm">OpenSky registration procedure</A> (which is in italian language!). <H2><A NAME="ss2.8">2.8 What else?</A> </H2> <P>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. <P>Follows the schema: <P> <PRE> Smart-Card -> CAM -> Common Interface -> Sat Card (with support C.I.) </PRE> <P>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. <HR> <A HREF="Sat-HOWTO-3.html">Next</A> <A HREF="Sat-HOWTO-1.html">Previous</A> <A HREF="Sat-HOWTO.html#toc2">Contents</A> </BODY> </HTML>