Article, May 2007
By Hilton Kaufman,
a Member of the Chicago Computer Society
Obtained from APCUG with the author's permission for publication by APCUG member groups.
email@example.com (click to email author)
(This is part of a series of articles providing a brief explanation of the Internet. The previous article provided an overview and mentioned that there are separate issues of connections, addressing of messages, and available services.)
The method of connection into the Internet varies somewhat among users. At various points, telephone lines, coaxial cables, UHF relays, satellite shots, and a few other methods might be utilized to make the actual connections. It is even possible to bring a lap top computer into a coffee house and reach an internet connection starting with a radio link.
Typically a home or small office user will connect through a company known as an Internet Service Provider or ISP. These could be small local companies or giants, such as AOL, Earthlink, and AT&T-Yahoo. A large company establishes local routing centers known as Points of Presence or POPs to allow for local calls into the system. Small ISPs have local numbers but might also use POPs if covering an area of more than just a few miles. A large ISP might have over 2,000 POPs.
POPs have some equipment that receives the connection from the individual user and routes it to the server, a powerful dedicated computer, at the actual ISP location. The ISP then routes the message toward where it supposed to go, probably eventually through another ISP and POP. Trunk lines owned by a few major long distance telephone service providers are used to send messages across country in this process.
There are also sites known as redirection services. In some ways, they can be used to hide where a message is coming from and going to, but do have other purposes. For example, one can frequently change ISPs based on availability in local areas and price, but keep a constant address with a redirection service. These services might also provide things like a personal web site, useful software, and online storage.
I live in Chicago, Illinois and use a redirection service in California. My ISP also is in California. If I receive a message, it is somehow sent to the redirection service in California; it then goes through my ISP; then to a POP somewhere in Chicago; then through my telephone switch center about three or four miles from where I live; and eventually to my computer.
The person sending me the message might live nearby, but use a different ISP. While the telephone switching center might be the same, the POP and ISP locations would be different. Another major ISP is located in Minnesota. Different trunk line connections would be used to send the message there and then over to by redirection service in California.
A small ISP might go directly into the trunk lines or work through a larger wholesale ISP. Various capacity heavy duty lines go to the ISPs which break down the capacity for individual users. The smallest of these heavy lines is known as a T1 and could be sufficient for a small ISP. A larger ISP or a POP for a major ISP might use a T3 line. Single user service over a T3 line would make normal broadband service look extremely slow, but costs thousands of dollars per month.
All of these connections take place in seconds.
Government entities, schools, large businesses, and some others might connect in to the Internet in other ways. A unit of government might have a connection to the Internet through a major ISP or might connect more directly into the trunk lines.
In Illinois, all Internet service for agencies under the governor is supposed to go through a Department of Central Management Services. A worker in Chicago searching for something at another site in Chicago would have to go through Springfield. The central agency probably connects to the trunk lines. The central agency for a state that centralizes its computer operations, as does Illinois, might be a computer operations agency or the state library.
Even municipalities might go through a state service. For example, to get to the Brooklyn Museum site at one time, one had go through a single site that served the entire State of New York. I tried this once from a Chicago Public Library public computer and received the message that the New York state computer was down; I then had to go the old fashioned encyclopedia that was on a shelf about 10 feet away to learn what I wanted.
Firewalls are used to protect data inside a network from outside tampering or prying. They can also be used to control what gets out. Firewalls can be set up at various levels to control access. In the other direction, if I send a message about something to one of my doctors, it will reach them among other messages on their hospital computers; but I cannot get in to see confidential information. One of the hospital systems, VA, can retrieve medical records across country, but no one else can get in. The other can exchange records among three hospitals and numerous scattered clinic sites.
Schools often act as small to moderate size ISPs. Faculty, staff, and students usually have internet privileges through the school. The schools might connect directly through the trunk, a large ISP, a state service, or another school. The main state university might serve as a central point for other schools in the state and have a direct connection to the trunk. ?
(The articles to follow in this series are concerned with Internet addressing, or how the system knows where to send things, and the services, such as e-mail, that are available.)
Hilton Kaufman serves as the technical support person for the procedures writing unit of an Illinois state agency, where higher level technical support personnel are concerned with the details of Internet connections and services. As such, he uses the software provided to him to create forms, convert documents into PDFs, advise members of his unit as to how to use the available software, and similar tasks. For his home computer, he can go all out and get a powerful machine that allows him to do things like playing games and surf the web without getting in trouble. He has prepared a number of articles aimed at novice users on the basics of standard computer programs.
This article has been provided to APCUG by the author solely for publication by APCUG member groups. All other uses require the permission of the author (see e-mail address above).Click here to return to top