5.3 Internet Access Technologies

High-rate digital subscriber line (HDSL)

A bidirectional high rate of service, suited for such services as videoconferencing. VHDSL (Very high rate digital subscriber line) is a variant which provides even higher transfer rates. (10Mbps and uses fiber-optics)

ISDN DSL (IDSL)

A symmetric type of DSL commonly used in environments in which SDSL and ADSL are unavailable. Does not support analog phones.

Rate-Adaptive DSL (RADSL)

A variation on ADSL that can modify its transmission speeds based on signal quality. Supports line sharing.

Cable Internet Access

Always on connection available through a coaxial connection or an Unshielded Twisted Pair (UTP) connection for connecting directly to a system or to a hub or switch. Costs comparable to DSL, although will generally be faster. Modems generally come with a medium-dependent interface crossed (MDI-X) port, so you can use a straight-through UTP cable to connect the modem to a system. Disadvantage is that you share available bandwidth with everyone else in your cable area.

POTS troubleshooting

Check physical connections, check for dial tone. Make sure user is dialing the correct number, check if ISP is having problems, check the modem speaker for busy signal. If DC: make sure modem is correctly configured, check the username/password, verify the connection settings, make sure user has not exceeded a preset time limit, try specifying a lower speed of connection.

DSL troubleshooting

Check physical connections, the NIC, drivers, protocol configuration, DSL LEDs,

plain old telephone system (POTS) service

Connect using a telephone line and modem. Modems convert the digital signals generated by a system into analog signals that can travel along the phone line. A dialup ISP account must also be obtained. 56Kbps is the fastest available.

Public Switched Telephone Network (PSTN)

Considered a POTS, is the entire collection of interconnected telephone wires throughout the world. Includes all the equipment. The cheapest way to create a WAN. Modern iteration is largely digital. Limited to 56K on modem and 128K with ISDN.

Cellular

Mobile data service. Long Term Evolution (LTE), often referred to as 4G because it is the fourth generation. Another tech is Worldwide Interoperability for Microwave Access (WiMax) (even faster). Evolved High Speed Packet Access (HSPA+) is known as a 3G transitional technology that supports legacy architecture.

Symmetric DSL (SDSL)

Offers the same speed for uploads and downloads, making it suitable for business applications such as web hosting, intranets, and e-commerce. Cannot share a phone line.

Asymmetric Digital Subscriber Line (ADSL)

Provides a high data rate in only one direction. Fast download speeds, but significantly slower upload speeds. Designed to work with existing analog plain old telephone service (POTS) service. Suited for home internet use where huge uploads are uncommon.

Satellite Internet Access

Provides a viable internet connection for those without access to other methods. Always on connection with speeds: 512K to 2048K. High cost and latency issues. One-way satellite system: outgoing: phone line, incoming: satellite. Two way: in/outgoing: satellite. Line of sight technology

Broadband Security Considerations

Since these connections are 'always-on,' a security risk is created. The longer you are online, the more likely it is that someone can remotely access your system. Attacks on an OS usually focus on email or open TCP/UDP ports. Combining security holes with an always on connection is a dangerous mix. Firewalls add protection via packet filtering and NAT. Also, be sure to keep your system completely updated.

DSL Internet

Uses a standard phone line to provide high speed. Often found in homes/small businesses. A different freq. can be used for dig/ana signals, which means you can use the phone while uploading data.

Wireless Internet Access

Wireless Internet Service Provider provides public wireless internet, known as hotspots. May or may not be free.