Levels of Internet Connectivity
Level one Connectivity:
Level One connectivity(gateway access') is access to the Internet from a network really is not on the Internet. Picture two circles that touch each other at only one point One of the circles is the Internet, the other circle is a non-Internet network, and the port where the two networks touch is called a gateway. (see Fig 3.4) the Gateway Figure 3.4 Level One Connectivity gateway allows the two networks to talk to each other but users of the non- Internet network are limited in their ability to fully access all of the tools available on the Internet.
With Level One connectivit, we are limited in what we can access on the Intemet what our service provider allows us to access. Good examples of networks with Level One connectivity are America CompuServe, Prodigy, and many of the other commercial on-line services. AOL is, in Online(AOL), effect, its own little network. It has a great number of different programs that its subscribers chat rooms), but ALL of these programs run only on the AOL network AOL subscribers, and subscribers to most of the other commercial on-line services, are lucky in that they can access SOME of the tools on the Internet through their gateway Many people with Level One connectivity only have e-mail access.
Level Two Connectivity:
Level Two connectivity Cremote modem access) is access through a diakup terminal connection. This is when, by use of a modem, a"host is accessed and our computer acts as if it were a terminal directly connected to that host. The host that we connect to is actually"on" the Internet, i.e. it is connected to the Internet by a full time level three" connection(see the next section, "Level Three Connectivity," for details).You may type the commands on your own computer, but it is the host that carries out your commands. Your computer is, in effect, just a"dumb' terminal connected to the host. Level Two connectivity is the most popular in the sense that more people have Level Two connectivity than any other level of connectivity
Level Two connectivity is also the most misunderstood level of connectivity As well, with Level Two connectivity you must always remember that everything you are doing is done through the host, NOT through your own computer. If you download a file from somewhere, that file will go to the host, NOT to your own personal computer You will need to download the file one more time this time from the host to your computer- if you want the file to be on YOUR computer.
Level Three Connectivity Level:
Three connectivity("'direct Internet access) is the highest, and most expensive, level of connectivity. With Level Three connectivity, our computer is directly wired into the Internet using high-speed lines, and is on-line twenty-four hours a day, seven days a week. Level Three connectivity is great if we have a mainframe or a major site with hundreds of users, but is not too advantageous if we are a sole user with a beat-up personal computer. Besides, Level Three connectivity is so incredibly expensive.
For example,the University of Alabama pays $29,000.00(US) every year just to connect to the Internet, and that doesn't include the software, hardware, facility, and staff expenses. Until recently, Level Three connectivity was limited to large corporations and universities who could afford the cost. Also, because Level Three connectivity is limited mostly to mainframes, you as a user are still limited to using the programs that are already loaded on the mainframe Thanks to some recent advances in modems and telephone lines, however,there isa new branch of Level Three connectivity called'On-Demand Direct Connectivity Since 0 inn to s24 hours a day on the Internet, there are some sitesout there that will let you connect directly to the Internet whenever you want using a high speed modem and something called"Point-to-Point Protocol(PPP)" or Serial Line Internet Protocol(SLIP) connection.
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