Internet Access Technologies


Internet access has become an integral part of modern business. There are several ways to obtain Internet access. The type chosen will often depend on the cost as well as what technologies are available in the area you are located. This section explores some of the more common methods of obtaining Internet access.

The term broadband is often used to refer to high-speed Internet access. Both DSL and cable modem are common broadband Internet technologies. Broadband routers and broadband modems are network devices that support both DSL and cable.


xDSL Internet Access

DSL is an Internet access method that uses a standard phone line to provide high-speed Internet access. DSL is most commonly associated with high-speed Internet access; because it is less expensive than technologies such as ISDN, it is often used in homes and small businesses. With DSL, a different frequency can be used for digital and analog signals, which means that you can talk on the phone while you're uploading data.

DSL arrived on the scene in the late 1990s, and it brought with it a staggering number of flavors. Together, all these variations are known as xDSL:

  • Asymmetric DSL (ADSL) Probably the most common of the DSL varieties is ADSL. ADSL uses different channels on the line: One channel is used for POTS and is responsible for analog traffic, the second channel is used to provide upload access, and the third channel is used for downloads. With ADSL, downloads are faster than uploads.

  • Symmetric DSL (SDSL) SDSL offers the same speeds for uploads and for downloads, making it most suitable for business applications such as Web hosting, intranets, and e-commerce. It is not widely implemented in the home/small business environment and cannot share a phone line.

  • ISDN DSL (IDSL) ISDN DSL is a symmetric type of DSL that is commonly used in environments where SDSL and ADSL are unavailable. IDSL does not support analog phones.

  • Rate Adaptive DSL (RADSL) RADSL is a variation on ADSL that can modify its transmission speeds based on the signal quality. RADSL supports line sharing.

  • Very High Bit Rate DSL (VHDSL) VHDSL is an asymmetric version of DSL and, as such, can share a telephone line.

  • High Bit Rate DSL (HDSL) HDSL is a symmetric technology that offers identical transmission rates in both directions. HDSL does not allow line sharing with analog phones.

Why are there are so many DSL variations? The answer is quite simply that each flavor of DSL is aimed at a different user, business, or application.

Businesses with high bandwidth needs are more likely to choose a symmetric form of DSL, whereas budget-conscious environments such as home offices are likely to opt for an option that allows phone line sharing at the expense of bandwidth. In addition, some of the DSL variants are simply older technologies. While the name persists, they have been replaced with newer DSL implementations. When you're working in a home/small office environment, you should expect to work with an ADSL system.

Table 6.5 summarizes the maximum speeds of the various DSL options. Keep in mind that maximum speeds are rarely obtained.

Table 6.5. DSL Speeds

DSL Variation

Upload Speed

Download Speed

ADSL

1Mbps

8Mbps

SDSL

1.5Mbps

1.5Mbps

IDSL

144Kbps

144Kbps

RADSL

1Mbps

7Mbps

VHDSL

1.6Mbps

13Mbps

HDSL

768Kbps

768Kbps


Cable Internet Access

Cable Internet access is an always on Internet access method that is available in areas that have digital cable television. Cable Internet access is attractive to many small businesses and home office users because it is both inexpensive and reliable. Most cable providers do not restrict how much use is made of the access. Connectivity is achieved by using a device called a cable modem; it has a coaxial connection for connecting to the provider's outlet and an Unshielded Twisted Pair (UTP) connection for connecting directly to a system or to a hub or switch.

Cable providers often supply a cable modem free of charge, although of course you are paying for the rental of the modem in a monthly service fee. Many cable providers offer free or low-cost installation of cable Internet service, which includes installing a network card in a PC. Some providers also do not charge for the network card. Cable Internet costs are comparable to DSL subscription.

Most cable modems supply a 10Mbps Ethernet connection for the home LAN, although you wouldn't expect the actual Internet connection to reach these speeds. The actual speed of the connection can vary somewhat depending on the utilization of the shared cable line in your area. In day-to-day application, data rates range from 1.5Mbps to 3Mbps.

A cable modem is generally equipped with a medium-dependent interface crossed (MDI-X) port, so a straight through UTP cable can be used to connect the modem to a system.


One of the biggest disadvantages of cable access is cited (by DSL providers at least) as the fact that you share the available bandwidth with everyone else in your cable area. As a result, during peak times, performance of a cable link might be poorer than in low-use periods. In residential areas, busy times are evenings and weekends, and particularly right after school. In general, though, performance with cable systems is good, and in low-usage periods, it can be very fast.

Although the debate between cable and DSL goes on, for us regular users, it really won't make that much difference which one we choose. Although cable modem technology delivers shared bandwidth within the local neighborhood, its speeds are marginally higher but influenced by this shared bandwidth. DSL delivers dedicated local bandwidth but is sensitive to distance that impacts overall performance. With the monthly costs about the same, it really is too close to call.


Broadband Security Considerations

Whether using DSL or cable Internet access, there are a few things to keep in mind. Each of these technologies offers always on service. This means that even when you are away from your computer, it is still on the Internet. As you can imagine, this creates a security risk. The longer you are online, the more chance someone has of remotely accessing your system.

The operating systems we use today all have some security holes through which some people are waiting to exploit. These attacks often focus on technologies such as email or open TCP/UDP ports. Combining OS security holes with an always on Internet technology is certainly a dangerous mix.

Today, DSL and cable Internet connections have to be protected by mechanisms such as firewalls to protect the system. The firewall system will offer features such as packet filtering and network address translation (NAT). The firewall can be a third-party software application installed on the system, or it can be a hardware device.

In addition to a firewall, it is equally important to ensure that the operating system you are using is completely up-to-date in terms of service packs and security updates. Today's client systems typically offer automatic update features that will alert you when a new security update is available.

Following a few safety rules, both DSL and cable Internet can provide safe Internet access. We just have to be security diligent.

POTS/PSTN (Plain Old Telephone Service/Public Switched Telephone Network)

The most popular means of connecting to the Internet or a remote network might still be the good old telephone line and modem.

Internet access through a phone system requires two things: a modem and a dial-up access account through an ISP. Modems are devices that convert the digital signals generated by a computer system into analog signals that can travel across a phone line. A computer can have either an internal or external modem. External modems tend to be less problematic to install and troubleshoot because they don't require reconfiguration of the host system. Internal modems use one of the serial port assignments (that is, a COM port) and must therefore be configured not to conflict with other devices.

The second piece of the puzzle, the dial-up ISP account, can easily be obtained by contacting one of the many local, regional, or national ISPs. Most ISPs offer a range of plans that are normally priced based on the amount of time the user is allowed to spend online. Almost without exception, ISPs offer 56Kbps access, the maximum possible under current standards. Most ISPs also provide email accounts, access to newsgroup servers, and often small amounts of Web space.

It is a good idea to research an ISP choice carefully. Free services exist, but they generally restrict users to a certain number of online hours per month or use extensive banner advertising to pay for the services. Normally, you pay a monthly service fee for an ISP; doing so provides a degree of reassurance because the ISP can be held accountable. Paid-for service also tends to provide a higher level of support.

Another big consideration for dial-up Internet access is how many lines the ISP has. ISPs never have the same number of lines as subscribers; instead, they work on a first-come, first-serve basis for dial-up clients. This means that on occasion, users get busy signals when they try to connect. Before signing up for a dial-up Internet access account, you should ask the company what its ratio of lines to subscribers is and use that figure as part of your comparison criteria.

Satellite Internet Access

Many of us take DSL and cable Internet access for granted, but these technologies are not offered everywhere. For areas where cheaper broadband options are not available, there are a limited number Internet options. One of the primary ones is Internet via satellite.

Satellite access provides a viable Internet access solution for those who cannot get other methods of broadband. Satellite Internet offers an always on connection with theoretical speeds advertised anywhere from 512Kbps upload speeds to 2048Kbps download speeds, considerably faster than a 56k dial-up connection. One of the primary drawbacks to satellite Internet is the cost, and even with the high price tag, it is not as fast as DSL or cable modem.

Although satellite Internet is slower and more costly than DSL or cable, it offers some very attractive featuresfirst of which has to be its portability. Quite literally, wherever you go, you can have Internet access. For business with remote users and clients, the benefit to this is clear. But the technology has far reaching impact; it is not uncommon to see RVs with a satellite dish on the roof. They have 24/7 unlimited access to the Internet as they travel.

There are many companies offering satellite Internet services, and a quick Internet search will reveal many. These Internet providers offer different Internet packages that vary greatly in terms of price, access speeds, and service. Some target business, whereas others are aiming for the private market.

Two different types of broadband Internet satellite services are deployed: one-way and two-way systems. A one-way satellite system requires a satellite card and a satellite dish installed at the end user's site; this system works by sending outgoing requests on one link using a phone line, with inbound traffic returning on the satellite link. A two-way satellite system, on the other hand, provides data paths for both upstream and downstream data. Like a one-way system, a two-way system also uses a satellite card and a satellite dish installed at the end user's site; bidirectional communication occurs directly between the end user's node and the satellite.

Home satellite systems are asymmetric; that is, download speeds are faster than upload speeds. In fact, a home satellite system is likely to use a modem for the upline traffic, with downloads coming over the satellite link. The exact speeds you can expect with satellite Internet depend on many factors. As with other wireless technologies, atmospheric conditions can significantly affect the performance of satellite Internet access. One additional consideration for satellite Internet is increased propagation timethe time it takes for the signal to travel back and forth from the satellite. In networking terms, this time is very high and an important consideration for business applications.

Wireless Internet Access

Not too long ago, it would have been inconceivable to walk into your local coffee shop with your laptop under your arm and surf the Web while drinking a latte. Putting aside the fact that beverages and laptops don't mix, wireless Internet access is everywhere and increasing.

Wireless Internet access is provided by a Wireless Internet Service Provider (WISP). The WISP provides public wireless Internet access known as hotspots. Hotspots provide Internet access for mobile network devices such as laptops, handheld computers, and cell phones in airports, coffee shops, conference rooms, and so on. A hotspot is created using one or many wireless access points near the hotspot location.

Client systems might need to install special application software for billing and security purposes; others require no configuration other than obtaining the network name (SSID). Hotspots do not always require a fee for service as companies use them as a marketing tool to lure Internet users to their businesses.

As of today, hotspots are not everywhere, but finding them is not difficult. Typically, airports, hotels, and coffee shops will advertise that they offer Internet access for customers or clients. In addition, WISP providers list their hotspot sites online so that they are easily found.

Establishing a connection to a wireless hotspot is a straightforward process. If not equipped with built-in wireless capability, laptops will require an external wireless adapter card. With the physical requirements of the wireless card taken care of, connect as follows:

  1. When you arrive at the hotspot site, power up your laptop. In some instances, you might need to reboot your system if it was on standby to clear out old configuration settings.

  2. The card might detect the network automatically. If this is the case, configuration settings, such as the SSID, will be automatically detected, and the wireless Internet will be available. If Internet access is free, there is little else to do; if it is a paid-for service, you will need to enter a method of payment. One thing to remember is to verify that you are using encryption for secure data transfer.

  3. If for some reason the wireless settings are not automatically detected, you will need to open up your wireless NICs configuration utility and manually set the configurations. These settings can include setting the mode to infrastructure, inputting the correct SSID, and setting the level of encryption used.

In addition to using a WISP, some companies such as hotels and cafes will provide wireless Internet access by connecting a wireless router to a DSL or cable Internet connection. The router becomes the wireless access point to which the users connect, and it allows clients to connect to the Internet through the broadband connection. The technology is based on the 802.11 standards, typically 802.11b/g, and client systems require only an internal or external wireless adapter.



    Network+ Exam Cram 2
    Network+ Exam Cram 2
    ISBN: 078974905X
    EAN: N/A
    Year: 2003
    Pages: 194

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