BILL'S GUIDE TO ADSL IN SPAIN

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What is it?  Who Does It? How Do I Get It?

What does ADSL stand for?

Asymmetric Digital Subscriber Line.

What is ADSL?

ADSL is a broadband connection technology which utilises existing copper wired telephone networks. ADSL uses a wide range of frequencies over an existing telephone line to deliver much higher speeds than your standard 56k modem (between 4 and 40 times faster). It is also possible to use your phone while online. The vast majority of ADSL customers in Spain will be on a 256/128 line.  They can receive data at up to 256kbs, and can send it at 128kbs.  By comparison, the fastest analog modem could only achieve a theoretical 56kbs.

Can I get it where I live?

You can find out from  the Ministry of Science and Technology using THIS LINK

How does it work?

The service makes use of your existing telephone line. It splits the signal into two channels, one for voice communications and the other for the high speed data connection. It makes use of a frequency range not used in normal voice communications:

Voice: 0 - 20 kHz
Data: 25.875 kHz - 1.104 MHz

Graphically, it looks like this:

Khz 0    20    40    60    80    100    120    140
RTB <---->
RDSI    <--------->
ADSL         <----------------------- upwards to 1.104 MHz

RTB is your ordinary analog (voice) telephone line.  Sometimes known as POTS (Plain Old Telephone System)

RDSI (also known as ISDN) is a dial-up digital connection, used for Internet connections before ADSL became available, and still in use where it is not yet available, or a cheaper alternative is required.

Do I still have to pay Telefonica line rental if I get ADSL?

What hardware and software do I need?

You will need either a Router or a USB modem.  You will probably be supplied with one or the other as part of the deal when you sign up for ADSL, and this may be a facotor in your choice of ISP.  Read what you're getting before agreeing!.  If you only have one computer, then a USB modem is probably easier to set up.  However, a Router will enable you to have all your family's computers connected to the Internet at the same time through the same ADSL connection using NAT (explained below). A router is completely independent of your computer, to which it will connect through a standard ethernet LAN card, and so can be used equally on a PC using Linux, or a MAC as well as a PC using Windows.  Although the software that the ISP supplies with the router assumes Windows, software for other systems can be downloaded or the router configured through a standard terminal program.

What can I do with it?

A simple answer to this would be: Anything you already do with your current 56k connection just much faster. However, you can do things that wouldn't be viable on a dialup connection:

• Play games with much lower latency.
• Multitask - download a file, browse the web, check email at the same time - all still much quicker than using a dial up connection.
• Streaming media - You can now watch high quality streaming media on your PC such as music videos, movie trailers, concerts, and even space shuttle launches!
• Some users now leave their systems running 24/7 and operate their pc remotely.

I've heard that the Spanish ISPs use NAT.  What is it?

NAT is an acronym for Network Address Translation. It operates as a solution to having multiple, global IP addresses. You can find more detail on my Technical page

So NAT is a good thing?

Generally, yes. NAT saves on IP allocation. It certainly helps me, as at any time I have between two and four computers connected through my ADSL connection using LAN.

Contention is basically sharing. You share your local ADSL capacity with others in the area.  The contention ratio is how many other users share your connection. I have been unable to find out what the contention level is for Spanish ISPs, but for BT - there are two levels of contention at the moment:

50:1 for the home user;
20:1 for the business user.

If you take the worst case scenario for the home user then that means you're sharing your 256kbs with 49 other people. If you are all downloading at the same time then you'll get 5kbs - about a tenth of the speed of a normal dial-up analogue modem.  However, the major ISPs guarantee a speed at least 10% of the maximum.  This is 25kbs, which is still only half of that achieveable by a dial-up modem!

Many ISPs are currently offering ADSL.  You can also subscribe directly with Telefonica.

ISPs are currently competing vigorously for market share.  This means that offers are changing quickly.  Please make sure you check the current position with the ISP of your choice.

Technical stuff - IPs, NAT, etc.

Words of wisdom from Bill Gray, an early adopter

My home page

Teltarifas.com (from whom much of this information came)

Telefonica (without whom .....)

Adslayuda A website in Spanish full of helpful content about ADSL in Spain