Internet Connections

Internet Connections Explained Cable, DSL, Dialup

Using a DSL Internet Connection

A standard telephone installation in the United States consists of a pair of copper wires that the phone company installs in your home. The copper wires have lots of room for carrying more than your phone conversations (they are capable of handling a much greater bandwidth, or range of frequencies, than that demanded for voice). DSL exploits this "extra capacity" to carry information on the wire without disturbing the line's ability to carry conversations. The entire plan is based on matching particular frequencies to specific tasks.

Precisely how much benefit you see will greatly depend on how far you are from the central office of the company providing the DSL service; as the connection's length increases, the signal quality decreases and the connection speed goes down. The limit for DSL service is 18,000 feet (5,460 meters), though for speed and quality of service reasons many DSL providers place a lower limit on the distances for the service. At the extremes of the distance limits, DSL customers may see speeds far below the promised maximums, while customers closer to the central office have faster connections and may see extremely high speeds in the future. DSL technology can provide maximum downstream (Internet to customer) speeds of up to 8 megabits per second (Mbps) at a distance of about 6,000 feet (1,820 meters), and upstream speeds of up to 640 kilobits per second (Kbps). In practice, the best speeds widely offered today are 1.5 Mbps downstream, with upstream speeds varying between 64 and 640 Kbps

When you have DSL installed, you will almost certainly be given small filters to attach to the outlets that don't provide the signal to your DSL modem. These filters are low-pass filters (simple filters that block all signals above a certain frequency). Since all voice conversations take place below 4 KHz, the low-pass (LP) filters are built to block everything above 4 KHz, preventing the data signals from interfering with standard telephone calls

One of the main differences between Internet service through DSL and through a cable modem is because cable-modem users generally share a network loop that runs through a neighborhood, adding users means lowering performance in many instances. DSL provides a dedicated connection from each user back to the Phone company, meaning that users won't see a performance decrease as new users are added.

Pros of using a DSL Internet Connection

Bandwidth is not shared with other users
Lower maximum speed than cable
Ability to network multiple computers to use one high-speed line

Cons of using a DSL Internet Connection

More likely to get a virus with out adequate antivirus software
No need for an extra phone line
Speed is determined by how far away from the Central Offices you are
The connection is more secure than with cable access
Special line filters are needed for non-DSL carrying outlets
“Always on” Internet connectivity

Using a Cable Modem Internet Connection

One might think that a television channel would take up quite a bit of electrical "space," or bandwidth, on a cable. In reality, each television signal is given a 6-megahertz (MHz, millions of cycles per second) channel on the cable. The coaxial cable used to carry cable television can carry hundreds of megahertz of signals, which translates to hundreds of potential channels.

When a cable company offers Internet access over the cable, Internet information can use the same cables because the cable modem system puts downstream data (data sent from the Internet to an individual computer) into a 6-MHz channel. On the cable, the data looks just like a TV channel. So Internet downstream data takes up the same amount of cable space as any single channel of programming. Upstream data (information sent from an individual back to the Internet) requires even less of the cable's bandwidth, just 2 MHz, since the assumption is that most people download far more information than they upload.

The downstream information flows to all connected users, just like in an Ethernet network (it's up to the individual network connection to decide whether a particular block of data is intended for it or not). On the upstream side, information is sent from the user to the Cable company (other users don't see that data at all). The narrower upstream bandwidth is divided into slices of time, measured in milliseconds, in which users can transmit one "burst" at a time to the Internet. The division by time works well for the very short commands, queries and addresses that form the bulk of most users' traffic back to the Internet

If you are one of the first users to connect to the Internet through a particular cable channel, then you may have nearly the entire bandwidth of the channel available for your use. As new users, especially heavy-access users, are connected to the channel, you will have to share that bandwidth, and may see your performance degrade as a result. It is possible that, in times of heavy usage with many connected users, performance will be far below the theoretical maximums. The good news is that this particular performance issue can be resolved by the cable company adding a new channel and splitting the base of users.

Another benefit of the cable modem for Internet access is that, unlike DSL, its performance doesn't depend on distance from the central cable office. A digital CATV system is designed to provide digital signals at a particular quality to customer households. On the upstream side, the burst modulator in cable modems is programmed with the distance from the head-end, and provides the proper signal strength for accurate transmission.

Pros of Using a Cable Modem Internet Connection

Higher maximum speed than DSL
Bandwidth is shared amongst all users
Ability to network multiple computers to use one high-speed line

Cons of Using a Cable Modem Internet Connection

More likely to get a virus with out adequate antivirus software
No need for an extra phone line
Not as secure a connection as DSL
“Always on” Internet connectivity

Internet Connection Sharing

A router is used to share one Internet connection among multiple networked PCs. Today, most of the routers on the market come with an integrated switch; the benefit of this is that you do not need to purchase an additional piece of equipment to network the computers together and to the internet. With a router installed, the bandwidth is dynamically divided among the attached computers giving the most bandwidth to the computers that need it.

Instant Messaging

There is no doubt that the Internet has changed the way we communicate. For many of us, e-mail has virtually replaced traditional letters and even telephone calls as the choice for correspondence. Every day, billions of e-mail messages are sent out. E-mail has been the most rapidly adopted form of communication ever known. In less than two decades, it has gone from obscurity to mainstream dominance.
In our fast-paced world, sometimes even the rapid response of e-mail is not fast enough. You have no way of knowing if the person you are sending e-mail to is online at that particular moment or not. Also, if you are sending multiple e-mails back and forth with the same person, you normally have to click through a few steps to read, reply and send the e-mail. This is why instant messaging (IM) has gained popularity.
Instant messaging allows you to maintain a list of people that you wish to interact with. You can send messages to any of the people in your list, often called a buddy list or contact list, as long as that person is online. Sending a message opens up a small window where you and your associate can type in messages that both of you can see.

Online Protection

Viruses Protection for Your internet Connection.

Viruses are malicious pieces of code that, when executed, can have a variety of effects. While some simply slow your computer down, there are others that can destroy all information on your computer, allow hackers access to nearly every aspect of the machine, and bring huge companies to their knees. While the best protection against a virus is simply isolating your computer from the world (no internet, no e-mail, no installed programs that you do not have the original CD’s for) there are a few methods that allow you to safeguard your computer; one method is to have adequate antivirus software with the latest updates (we recommend Norton Antivirus 2003)

Firewall Protection for your Internet Connection.

A firewall protects networked computers from intentional hostile intrusion that could compromise confidentiality or result in data corruption or denial of service. It may be a hardware device (see Figure 1) or a software program (see Figure 2) running on a secure host computer. In either case, it must have at least two network interfaces, one for the network it is intended to protect, and one for the network it is exposed to. A firewall sits at the junction point or gateway between the two networks, usually a private network and a public network such as the Internet. The earliest firewalls were simply routers. The term firewall comes from the fact that by segmenting a network into different physical sub networks, they limited the damage that could spread from one subnet to another just like firedoors or firewalls.

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