If you aren't familiar with some of the terms used on this page, you may refer to our computer acronyms web page for the definitions.

The diagram below is a simplified explanation of how UTD connects to the Internet. The upper left-hand portion is a very simple representation of our network. Essentially, all computing equipment at UTD is connected together through twisted pair cables and fiber in a 100Mb switched Ethernet LAN. When a machine on our network requests a connection to a "foreign" host (i.e. a host not on our LAN), that request travels over telephone lines to its destination.

The Internet is a huge cooperatively managed, distributed WAN using the worldwide telecommunications infrastructure as the vehicle to connect computer networks all over the world. Data travels through telephone lines (copper, fiber, satellite and microwave channels) to each network connected to the telecommunications system. If you look at the diagram, you will notice that when data leaves UTD, the first place it goes is the local CO for Southwestern Bell Telephone Company (labeled "public switch" in the diagram.) From there the data travels through three routers that belong to THENet and several that belong to Sprint before finally being routed to its destination.

The cloud with several servers in it represents the Internet and portrays the difficulty of defining the Internet accurately. No one entity controls the Internet, nor can anyone tell you precisely how many networks are connected to it. (Really, no network is connected to the Internet, because the Internet doesn't exist in the sense of a place networks can connect to. Networks are connected to each other through the telecommunications infrastructure as discussed above.)

One way to think about the data connections that interlink all the networks participating in the Internet is like a water distribution system. Every home has a small pipe feeding water to it. Each neighborhood has a larger pipe to feed the whole neighborhood, and so on, up to the source of the water. If the neighborhood pipe isn't large enough, the water pressure will drop, and it becomes more difficult to do things like water the lawn, wash dishes and take showers.

Using this analogy, the "source" of data for the Internet is the backbone; i.e. the major telecommunications companies that provide the distribution system for the data. Each NSP is analagous to a city or state distribution system. Each ISP is analogous to a neighborhood distribution system, and each individual machine on a network is analagous to a home in that neighborhood. When the ISP's "pipe" isn't big enough, the "pressure" drops, and it becomes harder and harder to do anything on the Internet. If the NSP's "pipe" is not big enough, the entire state or city suffers. And if the backbone isn't big enough, the entire system loses "pressure", and all networks will suffer.

To some degree, this has been happening on the Internet recently. The backbone providers, MCI, AT&T, Sprint, UUNET, GTE/BBNPlanet, et.al. have been suffering from slowdowns within their systems, because the Internet is growing so fast they can hardly order equipment fast enough to keep up with the demand. To get an idea of the problem and see if it's presently affecting your connection, you can visit some of their sites where they keep traffic statistics. (AT&T, Cable & Wireless, MAE EAST, MAE WEST and UUNET all have sites which report traffic statistics. For an overall view of worldwide Internet traffic, see the Internet Traffic Report.)