Internet Access Technologies
- Explain the characteristics and benefits of various WAN technologies.
- Given a scenario, install and configure equipment in the appropriate location using best practices.
Internet access has become an integral part of modern business. You have several ways to obtain Internet access. Which type you choose often depends on the cost and what technologies are available in your area. This section explores some of the more common methods of obtaining Internet access.
DSL Internet Access
Digital subscriber line (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 a relatively inexpensive Internet access, it is often found 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 upload data.
For DSL services, two types of systems exist: asymmetric digital subscriber line (ADSL) and high-rate digital subscriber line (HDSL). ADSL provides a high data rate in only one direction. It enables fast download speeds but significantly slower upload speeds. ADSL is designed to work with existing analog telephone service (POTS) service. With fast download speeds, ADSL is well suited for home-use Internet access where uploading large amounts of data isn’t a frequent task.
In contrast to ADSL, HDSL provides a bidirectional high-data-rate service that can accommodate services such as videoconferencing that require high data rates in both directions. A variant of HDSL is VHDSL (very high-rate digital subscriber line), which provides an HDSL service at very high data transfer rates.
DSL arrived on the scene in the late 1990s and 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, which uses different channels on the line. One channel is used for POTS and is responsible for analog traffic. The second channel provides upload access, and the third channel is used for downloads. With ADSL, downloads are faster than uploads, which is why it is called asymmetric DSL.
- Symmetric DSL (SDSL): Offers the same speeds for uploads and 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): A symmetric type of DSL commonly used in environments in which SDSL and ADSL are unavailable. IDSL does not support analog phones.
- Rate-adaptive DSL (RADSL): A variation on ADSL that can modify its transmission speeds based on signal quality. RADSL supports line sharing.
- Very high bit rate DSL (VHDSL or VDSL): An asymmetric version of DSL and, as such, can share a telephone line. VHDSL supports high-bandwidth applications such as VoIP and HDTV. VHDSL can achieve data rates up to approximately 10Mbps, making it the fastest available form of DSL. To achieve high speeds, VHDSL uses fiber-optic cabling.
- High bit rate DSL (HDSL): 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 enables phone line sharing at the expense of bandwidth. In addition, some of the DSL variants are simply older technologies. Although the name persists, they have been replaced with newer DSL implementations. When you work in a home/small office environment, you should expect to work with an ADSL system.
Table 6.6 summarizes the maximum speeds of the various DSL options. Maximum speeds are rarely obtained.
TABLE 6.6 DSL Speeds
DSL Troubleshooting Procedures
Troubleshooting DSL is similar to troubleshooting any other Internet connection. The following are a few things to check when users are experiencing problems with a DSL connection:
- Physical connections: The first place to look when troubleshooting a DSL problem is the network cable connections. From time to time, these cables can come loose or inadvertently be detached, and they are often overlooked as the cause of a problem. DSL modems typically have a minimum of three connections: one for the DSL line, one for the local network, and one for the power. Make sure that they are all plugged in appropriately.
- The network interface card (NIC): While you are checking the cable at the back of the system, take a quick look to see whether the network card LED is lit. If it is not, something could be wrong with the card. It might be necessary to swap out the network card and replace it with one that is known to be working.
- Drivers: Ensure that the network card is installed and has the correct drivers. Many times, simply using the most up-to-date driver can resolve connectivity issues.
- Protocol configuration: The device you are troubleshooting might not have a valid IP address. Confirm the IP address by using the appropriate tool for the operating system (and version of IP whether it be IPv4 or IPv6) being used—for example, ipconfig or ifconfig. If the system requires the automatic assignment of an IP address, confirm that the system is automatically set to obtain an IP address. It might be necessary to use the ipconfig /release and ipconfig /renew commands to get a new IP address.
- DSL LEDs: Each DSL box has an LED on it. The light sequences are often used to identify connectivity problems or problems with the box itself. Refer to the manufacturer’s website for specific information about error codes and LEDs, but remember the basics. A link light should be on to indicate that the physical connection is complete, and a flashing LED indicates that the connection is active.
Ultimately, if none of these steps cures or indicates the cause of the problem, you might have to call the DSL provider for assistance.
Cable Internet Access
Cable Internet access is an always-on Internet access method 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, switch, or router.
Cable providers often supply the cable modem, with a monthly rental agreement. 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 offer the ability to support a higher-speed Ethernet connection for the home LAN than is achieved. 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, the average nationwide average is approximately 32Mbps down and 9.6Mbps up. Figure 6.2 shows an example of speed test results.
FIGURE 6.2 Sample speed test results.
One of the biggest disadvantages of cable access is (by DSL providers, at least) 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 fast.
Cable Troubleshooting Procedures
In general, cable Internet access is a low-maintenance system with few problems. When problems do occur, you can try various troubleshooting measures:
- Check the user’s end: Before looking at the cable modem, make sure that the system is configured correctly and that all cables are plugged in. If a hub, switch. or router is used to share the cable Internet access among a group of computers, make sure that the device is on and correctly functioning.
- Check the physical connections: Like DSL modems, cable modems have three connections: one for the cable signal, one for the local network, and one for the power. Make sure that they are all appropriately plugged in.
- Ensure that the protocol configuration on the system is valid: If an IP address is assigned via Dynamic Host Configuration Protocol (DHCP), the absence of an address is a sure indicator that connectivity is at fault. Try obtaining a new IP address by using the appropriate command for the operating system platform you use. If the IP addresses are statically configured, make sure that they are correctly set. Trying to use any address other than that specified by the ISP might prevent a user from connecting to the network.
- Check the indicator lights on the modem: Most cable modems have indicator lights that show the modem’s status. Under normal conditions, a single light labeled Ready or Online should be lit. Most cable providers give the user a modem manual that details the functions of the lights and what they indicate in certain states. Generally, any red light is bad. Flashing LEDs normally indicate traffic on the connection.
- Cycle the power on the modem: Cycling the power on the modem is a surefire way to reset it.
- Call the technical support line: If you are sure that the connectors are all in place and the configuration of the system is correct, the next step is to call the technical support line of the cable provider. If the provider experiences problems that affect many users, you might get a message while you’re on hold, informing you of that. If not, you eventually get to speak to someone who can help you troubleshoot the problem. One of the good things about cable access is that the cable company can remotely monitor and reset the modem. The cable company should tell you whether the modem is correctly functioning.
Unless the modem is faulty, which is not that common, by this point the user should be back on the Internet, or at least you should fully understand why the user cannot connect. If the problem is with the cable provider’s networking equipment, you and the user simply have to wait for the system to come back on.
Broadband Security Considerations
Whether you use DSL or cable Internet access, keep a few things in mind. Each of these technologies offers always-on service. This means that even when you are away from your computer, it still connects to the Internet. As you can imagine, this creates a security risk. The longer you are online, the better the chances that someone can remotely access your system.
The operating systems in use today all have some security holes that attackers wait 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 must be protected by mechanisms such as firewalls. The firewall offers 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 use is completely up to date in terms of service packs and security updates. Today’s client systems typically offer automatic update features that alert you when a new security update is available.
If you diligently follow a few security measures, both DSL and cable Internet can provide safe Internet access.
Although it’s somewhat slow, one of the most popular means to connect to the Internet or a remote network may still be the good old telephone line and modem. Because the same line used for a household phone is used for dialup access, it is called the POTS (plain old telephone system) method of access. Although many parts of the world are served by broadband providers offering services such as those discussed so far in this chapter, some people still must (or choose to) connect with a modem.
Internet access through a phone system requires two things: a modem and a dialup 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 therefore must be configured not to conflict with other devices.
The second piece of the puzzle, the dialup ISP account, can easily be obtained by contacting one of the many local, regional, or national ISPs. Most ISPs offer a range of plans 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 carefully research an ISP choice. 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.
Another big consideration for dialup 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-served basis for dialup clients. This means that sometimes users get busy signals when they try to connect. Before signing up for a dialup Internet access account, ask the company what its ratio of lines to subscribers is, and use that figure as part of your comparison criteria.
With a modem and an ISP account, you are ready to connect. But what happens if things don’t go as you plan? Welcome to the interesting and sometimes challenging world of troubleshooting dialup connections.
Dialup Troubleshooting Procedures
Troubleshooting a dialup connection problem can be tricky and time-consuming, because you must consider many variables. Of the remote connectivity mechanisms discussed in this chapter, you are far more likely to have problems with a POTS connection than with any of the others. The following are some places to start your troubleshooting under various conditions.
If the user cannot dial out, try the following:
- Check physical connections: The most common problem with modem connections is that something has become unplugged; modems rarely fail after they initially work. For an external modem, you also need to verify that the modem has power and that it is connected to the correct COM port.
- Check that the line has a dial tone: You can do this by plugging a normal phone into the socket to see whether you can dial out. Also, a modem generally has a speaker, and you can set up the modem to use the speaker so that you can hear what is going on.
If the user can dial out but cannot connect to the network, try the following:
- Make sure that the user is dialing the correct number: This suggestion sounds obvious, but sometimes numbers change or are incorrectly entered.
- Call the ISP: You can call the ISP to determine whether it is having problems.
- Check the modem speaker: Find out whether you get busy signals from the ISP by turning on the modem speaker.
If the user can dial out and can get a connection but is then disconnected, try the following:
- Make sure that the modem connection is correctly configured: The most common modem configuration is 8 data bits, 1 stop bit, and no parity (commonly called eight-one-none).
- Check the username and password: Make sure that the correct username and password combination is configured for the dialup connection.
- Verify that the connection settings are correct: Pay particular attention to things such as the IP address. Nearly all ISPs assign IP addresses through DHCP, and trying to connect with a statically configured IP address is not permitted.
- Make sure that the user has not exceeded a preset connection time limit: Some ISPs restrict the number of monthly access hours. If the user has such a plan, check to ensure that some time credit is left.
- Try specifying a lower speed for the connection: Modems are designed to negotiate a connection speed with which both devices are comfortable. Sometimes, during the negotiation process, the line can be dropped. Initially setting a lower speed might get you a connection. You can then increase the modem speed to accommodate a better connection.
The Public Switched Telephone Network
The Public Switched Telephone Network (PSTN), often considered a POTS, is the entire collection of interconnected telephone wires throughout the world. Discussions of the PSTN include all the equipment that goes into connecting two points, such as the cable, the networking equipment, and the telephone exchanges.
The modern PSTN is largely digital, with analog connections existing primarily between homes and local phone exchanges. Modems are used to convert the computer system’s digital signals into analog so that they can be sent over the analog connection.
Using the PSTN to establish WAN connections is a popular choice, although the significant drawback is the limited transfer speeds. Transfer on the PSTN is limited to 56Kbps with a modem and 128Kbps with an ISDN connection, and it is difficult to share large files or videoconferencing at such speeds. However, companies that need to send only small amounts of data remotely can use the PSTN as an inexpensive alternative for remote access, particularly when other resources such as the Internet are unavailable.
Satellite Internet Access
Many people take DSL and cable Internet access for granted, but these technologies are not offered everywhere. Many rural areas do not have cable Internet access. For areas where cheaper broadband options are unavailable, a limited number of Internet options are available. One of the primary options 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 download speeds considerably faster than an old dialup connection. Satellite Internet access does have a few drawbacks, though, such as cost and high latency. Latency is the time it takes for the signal to travel back and forth from the satellite.
Although satellite Internet is slower and more costly than DSL or cable, it offers some attractive features, the first of which is its portability. Quite literally, wherever you go, you have Internet access with no phone lines or other cables. For businesses with remote users and clients, the benefit is clear. But the technology has a far-reaching impact; it is not uncommon to see recreational vehicles (RVs) with a satellite dish on the roof. They have 24/7 unlimited access to the Internet as they travel.
Many companies offer satellite Internet services; a quick Internet search reveals quite a few. These Internet providers offer different Internet packages that vary greatly in terms of price, access speeds, and service. Some target businesses, whereas others aim 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, in contrast, provides data paths for both upstream and downstream data. Like a one-way system, a two-way system 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. A home satellite system is likely to use a modem for the uplink 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 time—how long it takes the signal to travel back and forth from the satellite. In networking terms, this time is long and therefore is an important consideration for business applications.
Home Satellite Troubleshooting Procedures
Your ability to troubleshoot satellite Internet connections might be limited. Home satellite Internet is a line-of-sight wireless technology, and the installation configuration must be precise. Because of this requirement, many satellite companies insist that the satellite be set up and configured by trained staff members. If you install a satellite system in a way that does not match the manufacturer’s recommendations, you might void any warranties.
Given this limitation, troubleshooting satellite connections often requires you to concentrate less on connectivity issues and more on physical troubleshooting techniques. Perhaps more than for any other Internet technology, calls to technical support occur early in the troubleshooting process. Satellite Internet has a few aspects that you should be aware of:
- Rain fade: Refers to signal loss due to moisture interference. The general rule is that the smaller the dish, the more susceptible it is to rain fade. Home and small businesses use small dishes.
- Latency: Refers to the time lapse between sending or requesting information and the time it takes to return. As you might expect, satellite communication experiences high latency due to the distance it has to travel.
- Line of sight: Despite the distance, satellite is basically a line-of-sight technology. This means that the path between the satellite dish and the satellite should be as unobstructed as possible.
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 that beverages and laptops don’t mix, wireless Internet access has become common.
Wireless Internet access is provided by an ISP providing public wireless Internet access known as hotspots. Hotspots offer 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 (service set identifier [SSID]). Hotspots do not always require a fee for service because companies use them as a marketing tool to lure Internet users to their businesses.
Hotspots are not everywhere, but finding them is not difficult. Typically, airports, hotels, and coffee shops advertise that they offer Internet access for customers or clients. In addition, ISPs 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 require an external wireless adapter card. With the physical requirements of the wireless card taken care of, connect as follows:
- When you arrive at the hotspot site, power up your laptop or other mobile device. In some instances, you might need to reboot your system if it was on standby to clear out old configuration settings.
- The card might automatically detect the network. If this is the case, configuration settings, such as the SSID, are automatically detected, and the wireless Internet is available. If Internet access is free, there is little else to do; if it is a paid-for service, you need to enter a method of payment. One thing to remember is to verify that you use encryption for secure data transfer.
- If for some reason the wireless settings are not automatically detected, you need to open your wireless NIC’s 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 an ISP, some companies such as hotels and cafes 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 enables clients to connect to the Internet through the broadband connection. The technology is based on the 802.11 standards, typically 802.11n/ac today, and client systems require only an internal or external wireless adapter.
Just as POTS can serve as a means to connect to the Internet, so, too, can the cellular network. When the cellular network is used for this purpose, it is often marketed as a mobile data service and uses a wireless NIC to connect the mobile device or desktop to the network.
One technology that enables this is Long-Term Evolution (LTE), which is often referred to as 4G because it is the fourth generation in a long series of products offering similar services. Another technology is Worldwide Interoperability for Microwave Access (WiMAX), which is based on 802.16. Table 6.7 shows peak upload and download speeds for both LTE and WiMAX. Actual implementations by carriers vary but are always below the theoretical possibilities.
TABLE 6.7 LTE and WiMax Speeds
Peak Upload Speed
Peak Download Speed
Evolved High Speed Packet Access (HSPA+) is known as a 3G transitional technology that supports legacy architecture. It can offer theoretical upload speeds of 22Mbps and downloads of 84Mbps.
Edge, an acronym for enhanced data rates for GSM evolution, is a technology that is backward compliant and provides faster data rates (3G) on the GSM standard. Networks built for Edge are used to deliver streaming data at speeds up to 384Kbps (slow by most standards but faster than GSM).
Which of the following technologies require dialup access? (Choose the two best answers.)
- A. FDDI
- B. ISDN
- C. Packet switching
- D. The PSTN
Which of the following is an advantage of ISDN over the PSTN?
- A. ISDN is more reliable.
- B. ISDN is cheaper.
- C. ISDN is faster.
- D. ISDN uses 53Kbps fixed-length packets.
Which of the following technologies is known as a 3G transitional technology that supports legacy architecture?
- A. HSPA+
- B. LTE
- C. WiMAX
- D. PON
What is the theoretical download speed possible with WiMAX?
- A. 84Mbps
- B. 100Mbps
- C. 1Gbps
- D. 10Gbps
Which of the following is the time lapse between sending or requesting information and the time it takes to return?
- A. Echo
- B. Attenuation
- C. Bandwidth
- D. Latency
What is the speed usually offered with dialup service?
- A. 1Gbps
- B. 256Kbps
- C. 144Kbps
- D. 56Kbps
Cram Quiz Answers
- B and D. Both the PSTN and ISDN require dialup connections to establish communication sessions.
- C. One clear advantage that ISDN has over the PSTN is its speed. ISDN can combine 64Kbps channels for faster transmission speeds than the PSTN can provide. ISDN is no more or less reliable than the PSTN. ISDN is more expensive than the PSTN.
- A. HSPA+ (Evolved High Speed Packet Access) is known as a 3G transitional technology that supports legacy architecture.
- C. The theoretical download speed possible with WiMAX is 1Gbps. The speed possible with HSPA+ is 84Mbps, whereas that possible with LTE is 100Mbps.
- D. Latency refers to the time lapse between sending or requesting information and the time it takes to return.
- D. Almost without exception, ISPs offer 56Kbps access, the maximum possible under current standards.