Part 2 - How We Connect and Reach the Net by Dudette
In general, there are three ways that devices like computers and WebTVs connect to the Internet.
A Permanent Connection
The first way is a permanent connection to the Net over a "dedicated" (and, often, high-speed) phone line. Servers that host web pages connect this way -- they're always connected (or so their webmasters hope), and they have a permanent address or IP number.
The IP address is how the data packets find their way from one computer to the other. Special switches call "routers" read the IP address on the packet's "envelope" and send it on to a router closer to the computer it's meant for.
If you request a page from a site with a domain name, like www.net4tv.com, special servers on the Net called "Domain Name Servers" act like Directory Assistance operators -- looking up the domain name and getting the IP address for it to put on the envelope.
Dial-Up Connection with Dynamic Address
The second way, the way most PC users connect from home, is over a dial-up connection. Generally, once the user has logged in, the ISP lends the computer an IP address to use for the online session. This is called a "dynamic IP" and, when the user logs off, the IP address is freed to be handed out to another user logging on.
In the old days (all of three or four years ago), even dial-up connections had permanent or "static" IP numbers. But now, with so many people online, IP numbers are in very short supply, so permanent IPs are generally not used for dialup any more.
Even though you're only using the IP number temporarily, the data you're looking for can find you because the ISP who owns the IP number is permanently attached to the Net. The data is sent to the ISP portion of the address and then on down its network to your computer's specific address.
Proxy Servers
The third way, which is used both by WebTV and AOL, is a proxy server connection. A "proxy" is someone who does something on your behalf, and what the proxy server does for you is request and send data onto the Net.
When you come onto the Net via a proxy server, the server actually does the data requests for you. When you request a Web page, for example, you're not actually throwing the request out onto the Net as you do with the permanent and dialup connections we talked about above.
Instead, you ask the proxy server to go get it for you. The proxy server takes one of its IPs and sends it out to the server that has the Web page you want with its request. The server packages the data and addresses it to the proxy server. When the proxy server receives it, it delivers it to you.
WebTV's Proxy Server
So why add this extra step? One advantage is that a lot of computers or WebTV boxes using a proxy server can surf on a very few IP addresses -- the proxy server keeps track of who asked for what.
Another reason is security, although this applies more to computers with sensitive data stored on their hard disks. A computer that's attached directly to the Net can be penetrated from the Net. A proxy server can function as a sort of firewall for its clients (PCs or WebTVs).
WebTV's proxy server also processes the data to make it more "TV friendly" -- for example, pulling the colors of the graphics down from "computer colors" to colors that the TV can display. It then compresses it to make it smaller and faster to transmit, and sends it down the modem line to the box.
WebTV: A "Thin Client"
The WebTV unit is a computer. But it's a special type of computer called a "thin client" that must run with its matching server, or it won't run at all.
The reason is that part of the software that makes it run is on the server, not in the box at all. When the WebTV connects to the server, much of the work that would take place on a PC is taken care of by the server. Email and favorites and user names are on the server, for example, not in the WebTV box itself.
An advantage of the "thin client" approach is cost. If the heavy lifting and storage is on the server, then the box doesn't have to have a lot of power or memory. This is how WebTV has been able to deliver so much in such a low-cost box -- with high-cost servers doing most of the work.
WebTV occasionally downloads an upgrade into our boxes, but "server side upgrades" and software maintenance can be done any time. The addition of the "Fetch" POP3 feature to email was a server-side upgrade.
The other thing that this approach provides (for WebTV itself) is control of the clients. Since user email and personal information is stored on the server and every thing you do on line goes through the server, WebTV has access to every piece of information available about who its users are and what they do, every minute they are on line.
"Thin client" users can't decide to change services, as PC users can if they get tired of AOL. "Churn" (user turnover) rate of a thin client service should be lower, but as we saw with NetChannel, discontinuance of the service by the network turns the box into a bookend.
Most of the Internet settop boxes will likely be thin clients. They allow a functional, low-cost "appliance" that does not need any technical knowledge in order to be fully enjoyed. Over the next year, we're likely to begin to see cable modem "thin clients" offering the Internet at blazing speeds. In future part of "How the Internet Works," we'll look at the next generation and how it will change how we surf.
Next Time...
In our next issue, we really will look at how the browser actually draws the web page on your TV or computer screen. (We'd planned it for this time, but got so many questions we decided to explain this part first.) In the meantime, we'd appreciate your feedback to know if this sort of information is interesting and/or useful to you.
